%R 2023HEAD...2016115S %T Chandra Observation of the Large Magellanic Cloud Supernova Remnant J0550-6823 %A Seward, Frederick %F AA(Harvard Smithsonian Center for Astrophysics) %J AAS/High Energy Astrophysics Division %V 20 %D 09/2023 %P 116.115 %C Copyright 2023 the American Astronomical Society %I ABSTRACT: Abstract; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/2023HEAD...2016115S %B Radio, optical, and X-ray observations of this rather faint, old, LMC supernova remnant are described. The [OIII] emission forms a distinct shell, the remnant of the Outer Shock, which encloses the radio and X-ray emission and gives an estimate of age and explosion energy. Because of a collision with an LMC Hα filament, radio and X-ray emission are concentrated in the northern half of the remnant. The X-ray spectrum is almost solely lines from O, Ne, Mg, and Fe. The known distance, low extinction, and low ISM metallicity, allow derivation of masses of several elements produced by the star and in the explosion. Masses of O, Ne, and Fe point to a Type II Supernova from the explosion of a 20-25 M star. The mass of Mg, however, is higher than that of almost all predictions. In the background, a radio-bright AGN appears just outside the shell of the remnant. %R 2023ApJ...950...74S %T The Large Magellanic Cloud Supernova Remnant MCSNR J0550-6823 %A Seward, Frederick D.; Points, Sean D. %F AA(Smithsonian Astrophysical Observatory), AB(Cerro Tololo Interamerican Observatory) %J The Astrophysical Journal %V 950 %D 06/2023 %P 74 %K X-ray astronomy, Large Magellanic Cloud, Type II supernovae, Supernova remnants, 1810, 903, 1731, 1667 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I PUB_HTML: Publisher Article; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %U https://ui.adsabs.harvard.edu/abs/2023ApJ...950...74S %B We describe radio, optical, and X-ray observations of this rather faint, old Large Magellanic Cloud (LMC) supernova remnant. The [O III] emission forms a distinct shell, the remnant of the outer shock, which encloses the radio and X-ray emission and gives an estimate of age and explosion energy. Because of a collision with an LMC Hα filament, radio and X-ray emission are concentrated in the northern half of the remnant. The X-ray spectrum is well fit assuming the plasma is isothermal and in collisional equilibrium. The best-fit temperature is such that almost all energy is in lines from O, Ne, Mg, and Fe. The known distance, low extinction, and low interstellarmedium metallicity allow derivation of masses of several elements produced by the star and in the explosion. The masses of O, Ne, and Fe point to a Type II supernova from the explosion of a 20-25 M _⊙ star. The mass of Mg, however, is higher than that of almost all predictions, but some of this apparent excess might be due to a higher-temperature region in the X-ray-emitting material. Point-like background sources are examined to search for a neutron star, and one possible candidate is found just inside the shell of the remnant. %H IOP %Y DOI: 10.3847/1538-4357/acc656 %R 2021ApJ...909...13S %T XMM Observation of the Supernova Remnant J0454-6713 and the Adjacent N9 Superbubble %A Seward, Frederick D.; Foster, Adam R.; Smith, Randall K.; Points, Sean D. %F AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory), AC(Smithsonian Astrophysical Observatory), AD(Cerro Tololo Interamerican Observatory) %J The Astrophysical Journal %V 909 %D 03/2021 %P 13 %K Supernova remnants, Large Magellanic Cloud, X-ray astronomy, Plasma astrophysics, Type Ia supernovae, 1667, 903, 1810, 1261, 1728 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %I XMM: XMM Newton Science Archive; %U https://ui.adsabs.harvard.edu/abs/2021ApJ...909...13S %B The Large Magellanic Cloud supernova remnant J0454-6713 abutting the H II region N9 has been observed with XMM-Newton. Two groups of lines from Fe XVII account for half the emission and lines from Fe XVIII, O VII, and O VIII are also clearly detected with the XMM RGS. Isothermal equilibrium fits of the EPIC spectra reproduce the basic spectral form and show little variation throughout the remnant but are insensitive to the lines from the high-temperature ions. These are overwhelmed in the EPIC cameras by the dominant Fe XVII radiation and the EPIC best-fit spectra do not agree with the RGS data. Uncertainties in the atomic data used to determine Fe-line strength present a further complication which inhibits a good EPIC spectral fit. We build a two-temperature model which does fit both RGS and EPIC results and propose that the high-T component is from SN debris and the low from heated material in the H II region. The high ratio of Fe emission to that from O requires the remnant to be the product of a Type Ia supernova and points to a deflagration-detonation origin. Weak X-ray emission from the N9 superbubble is detected and briefly discussed. The abundance of Ne in N9 material seems higher than average for the LMC in both the superbubble spectrum and the low-temperature component of the remnant RGS spectrum. %H IOP %Y DOI: 10.3847/1538-4357/abd561 %R 2018ApJ...861..154S %T J0453-6655, the Supernova Remnant in N4D %A Seward, F. D.; Smith, R. K.; Slane, P. O.; Murray, S. S.; Points, S. D.; Gordon, A. J. R.; Dickel, J. R. %F AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory), AC(Smithsonian Astrophysical Observatory), AD(Smithsonian Astrophysical Observatory), AE(Cerro Tololo Interamerican Observatory), AF(Macalester College, Minnesota), AG(University of New Mexico, Department of Physics and Astronomy) %J The Astrophysical Journal %V 861 %D 07/2018 %P 154 %K H ii regions, ISM: supernova remnants, Magellanic Clouds %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %I HEASARC: NASA's High Energy Astrophysics Science Archive Research Center; %I XMM: XMM Newton Science Archive; %U https://ui.adsabs.harvard.edu/abs/2018ApJ...861..154S %B The Large Magellanic Cloud supernova remnant J0453-6655 in the H II region N4 has been observed with XMM-Newton and with Chandra. Almost all of the diffuse X-ray emission is from within a 3.‧5 × 2.‧3 region of bright optical filaments, and X-ray results from XMM-Newton and Chandra are very similar. Spectra indicate that the plasma is close to equilibrium and that the remnant is likely the result of a Type II supernova powered by the collapse of a <12 M _⊙ star. Composition, density, and mass of the X-ray-emitting plasma are derived, and the age of the remnant is estimated to be 60-80 kyr. There is an apparent blowout of energy into an adjoining cavity. Because cooling neutron stars are objects of interest, the surrounding sky is searched for possible compact remnants of the core. There are six point-like sources within the remnant, all rather faint. Two are probably background active galactic nuclei. The others have soft spectral components and no IR counterparts, but, with the present data, none can be proved to be a neutron star. They do represent upper limits to any neutron star luminosity. %H IOP %Y DOI: 10.3847/1538-4357/aabf43 %R 2015xmm..prop...67S %T The Spectrum of the Magellanic Cloud Supernova Remnant 0454-67.2 in N9 %A Seward, Frederick %J XMM-Newton Proposal %D 10/2015 %P 67 %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/2015xmm..prop...67S %B The supernova remnant 0454-67.2 in the northwest wing of the LargeMagellanic Cloud is cooling and has faded to the point where most ofthe X-ray emission is in lines of O and Fe below 1 keV. These energiesand the remnant geometry are well suited to the XMM RGS spectrometer,making it possible to get important information from this low-luminosityobject. We will to measure the abundance and temperature of O, Ne, and Fein the central region and confirm (or not) the Type Ia identification. Wewill then use the measured line ratios to directly estimate the ionizationage of the remnant and, using the morphology measured by EPIC and byChandra, calculate the mass of Fe in the central region. There may alsobe evidence for overionized plasma as in some 'mixed morphology'remnants. %R 2014fysc.confP..58S %T Where are the Low-mass Neutron Stars? %A Seward, Frederick %F AA(Smithsonian Astrophysical Observatory) %J 15 Years of Science with Chandra %D 11/2014 %P P58 %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/2014fysc.confP..58S %B Neutron stars are predicted to be stable over the mass range ≈0.1 to ≈3 M⊙. At 1.4 M⊙, 98% of the mass is in a core with supernuclear density and 1-2 % forms a thin crust and atmosphere. As mass decreases, the fraction of mass in the crust increases until at 0.1 M⊙, all material is at nuclear density or below and the star is all crust. Observationally, the masses of ≈ 60 neutron stars have been measured and all fall between 1 M⊙ and 2 M⊙. It is of interest to search for low-mass neutron stars, those with M < 0.5 M⊙. These should have different characteristics and might be found in high-mass binaries, as high-velocity objects, and perhaps as Magnetars. %R 2013ApJ...769...17S %T Azimuthal Structure of the Cyg X-2 X-Ray Dust Halo %A Seward, F. D.; Smith, R. K. %F AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory) %J The Astrophysical Journal %V 769 %D 05/2013 %P 17 %K dust, extinction, X-rays: individual: Cyg X-2 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I PUB_HTML: Publisher Article; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/2013ApJ...769...17S %B There is little information concerning the azimuthal distribution of X-rays in dust-scattering halos. This paper describes a Chandra observation of the bright source Cyg X-2 designed specifically for this purpose. After measuring and subtracting ≈10% instrument effects, we find the scattering halo to be rather uniform with possible fluctuations in the surface brightness of only 2%. Observations and data processing are discussed in detail. Some information about the dust distribution is derived. %H IOP %Y DOI: 10.1088/0004-637X/769/1/17 %R 2013AAS...22111312S %T X-ray Astronomy at Lawrence Livermore Laboratory 1965-1975 %A Seward, Frederick D. %F AA(Harvard Smithsonian Center for Astrophysics) %J American Astronomical Society Meeting Abstracts #221 %V 221 %D 01/2013 %P 113.12 %C (c) 2013: American Astronomical Society %I ABSTRACT: Abstract; %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/2013AAS...22111312S %B In 1965 a group of nuclear physicists at the Livermore Laboratory started to make observations of the X-ray sky. They found themselves in a unique situation - easy access to sounding rocket flights and generous support for instrument buiding and data analysis. The program continued for ten years. With rocket-borne detectors we showed that Sco X-1 was a thermal source and measured its approximate size and density. New sources were discovered in the southern sky including a bright transient and two luminous sources in the Large Magelanic Cloud. Detectors were developed for sub keV X-rays and three old supernova remnants were found to be the brightest sources in this energy band. These astronomy observations provided inspiration and challenge to the rocket development program and, in addition to these discoveries, a resource useful for the nation's interests was developed. %R 2012ApJ...759..123S %T DEM L241, a Supernova Remnant Containing a High-mass X-Ray Binary %A Seward, F. D.; Charles, P. A.; Foster, D. L.; Dickel, J. R.; Romero, P. S.; Edwards, Z. I.; Perry, M.; Williams, R. M. %F AA(Smithsonian Astrophysical Observatory), AB(University of Southampton, School of Physics and Astronomy; University of Cape Town, Department of Astronomy), AC(South African Astronomical Observatory; Vanderbilt University, Department of Physics and Astronomy), AD(University of New Mexico, Department of Physics and Astronomy), AE(University of New Mexico, Department of Physics and Astronomy), AF(Columbus State University), AG(Columbus State University), AH(Columbus State University) %J The Astrophysical Journal %V 759 %D 11/2012 %P 123 %K ISM: supernova remnants, Magellanic Clouds, X-rays: binaries, X-rays: individual: DEM L241, Astrophysics - High Energy Astrophysical Phenomena %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I EPRINT_HTML: arXiv Article; %I PUB_HTML: Publisher Article; %I EPRINT_PDF: arXiv PDF; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %I HEASARC: NASA's High Energy Astrophysics Science Archive Research Center; %I XMM: XMM Newton Science Archive; %U https://ui.adsabs.harvard.edu/abs/2012ApJ...759..123S %B A Chandra observation of the Large Magellanic Cloud supernova remnant DEM L241 reveals an interior unresolved source which is probably an accretion-powered binary. The optical counterpart is an O5III(f) star making this a high-mass X-ray binary with an orbital period likely to be of the order of tens of days. Emission from the remnant interior is thermal and spectral information is used to derive density and mass of the hot material. Elongation of the remnant is unusual and possible causes of this are discussed. The precursor star probably had mass >25 M _⊙ %H IOP %Y DOI: 10.1088/0004-637X/759/2/123 %Y eprintid: arXiv:1208.1453 %R 2012AAS...21923917M %T The X-ray Structure Of The Supernova Remnant And Pulsar-wind Nebula in DEM L 241 %A Murphy Williams, Rosa Nina; Seward, F.; Dickel, J.; Edwards, Z.; Furnish, B.; Perry, M.; Williams, T. %F AA(Columbus State University), AB(Harvard Smithsonian Center for Astrophysics), AC(University of New Mexico), AD(Columbus State University), AE(Columbus State University), AF(Columbus State University), AG(Columbus State University) %J American Astronomical Society Meeting Abstracts #219 %V 219 %D 01/2012 %P 239.17 %C (c) 2012: American Astronomical Society %I ABSTRACT: Abstract; %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/2012AAS...21923917M %B High energy astrophysics offers us the ability to further understand pulsars (PSR), pulsar wind nebulae (PWN), and their interaction with the host supernova remnant (SNR). SNR DEM L241, located in the Large Magellanic Cloud, allows us to study a complex SNR in close proximity and low absorption. DEM L241 is also ideal for this study due to the separation of the internal PSR and PWN. Using data provided by the Chandra Space Telescope we were able to analyze spatially resolved spectra and calculate physical properties for various regions of the remnant in order to better understand the evolution of the SNR and PWN, and their interactions with each other and the interstellar medium.

The authors thank NASA's Chandra grant G01-12094C and LTSA grant NNX08AM54G for support of this project. %R 2010cxo..prop.3135S %T The Pulsar Wind Nebula in DEM L241 %A Seward, Frederick %J Chandra Proposal %D 09/2010 %P 3135 %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/2010cxo..prop.3135S %X Chandra proposal ID #12500668 %B DEM L241 is a moderately bright SNR in the Large Magellanic Cloud. XMM has revealed but not resolved a PWN inside this remnant. Chandra's arcsec resolution makes possible a search for structure within the PWN and for the PSR itself as a point source. Any structure observed in the thermal part of the remnant will help determine age and evolution. Results will be particularly useful added to Chandra observations of 33 other MC remnants, 8 of which contain compact sources or PWN. %R 2010exru.book.....S %T Exploring the X-ray Universe %A Seward, Frederick D.; Charles, Philip A. %J Exploring the X-ray Universe by Frederick D. Seward and Philip A. Charles. Cambridge University Press %D 08/2010 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I Co-Reads: Co-Reads; %I LIBRARY: Library Entry; %I PUB_HTML: Publisher Article; %I PUB_PDF: Publisher PDF; %U https://ui.adsabs.harvard.edu/abs/2010exru.book.....S %B 1. Birth and childhood of X-ray astronomy; 2. X-ray emission and interaction with matter; 3. Tools and techniques; 4. Solar System X-rays; 5. X-ray absorption and scattering in the interstellar medium; 6. Active stellar coronae; 7. Early-type stars; 8. Supernova explosions and their remnants; 9. Neutron stars, pulsars, pulsar wind nebulae, more supernova remnants; 10. Cataclysmic variable stars; 11. X-ray binaries; 12. Black-hole X-ray binaries; 13. Normal and starburst galaxies; 14. Active galactic nuclei; 15. Clusters of galaxies; 16. The diffuse X-ray background; 17. Gamma-ray bursts; Index. %R 2010AJ....140..177S %T A Chandra Observation of SNR 0540 - 697 %A Seward, F. D.; Williams, R. M.; Chu, Y. -H.; Gruendl, R. A.; Dickel, J. R. %F AA(Smithsonian Astrophysical Observatory), AB(Columbus State University), AC(University of Illinois, Urbana-Champaign, Department of Astronomy), AD(University of Illinois, Urbana-Champaign, Department of Astronomy), AE(University of New Mexico, Department of Physics and Astronomy) %J The Astronomical Journal %V 140 %D 07/2010 %P 177 %L 183 %K dust, extinction, H II regions, ISM: supernova remnants, Magellanic Clouds, techniques: image processing, X-rays: individual: SNR 0540 – 697 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I PUB_HTML: Publisher Article; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %U https://ui.adsabs.harvard.edu/abs/2010AJ....140..177S %B This paper describes a Chandra observation of SNR 0540 - 697 within the H II complex N159 in the Large Magellanic Cloud (LMC). Scattering from the nearby bright source LMC X-1, which obscures the western edge of the remnant, has been removed. Larger than previously believed, the 2farcm0 × 2farcm8 remnant is defined by optical filaments and two lobes of X-ray emission. A band of intervening material absorbs X-rays from the central part of the remnant. The N Lobe of the remnant is relatively bright and well defined, while emission from the S Lobe is much weaker. There is structure within the N Lobe but no clear X-ray emission from an outer shell indicating a shock in the interstellar medium. The X-ray spectrum is thermal with emission lines from Fe, Mg, and Si. The observed temperature and luminosity of the hot gas are 0.6 keV and 6 × 10³⁵ erg s^-1, respectively. These are consistent with characteristics expected for older remnants. There is also diffuse thermal X-ray emission north of N159 extending into N160, evidence for a larger remnant or bubble. %H IOP %Y DOI: 10.1088/0004-6256/140/1/177 %R 2010HEAD...11.1805S %T A Chandra Observation of SNR 0540-697 %A Seward, Frederick D.; Williams, R.; Chu, Y.; Dickel, J.; Gruendl, R. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Columbus State University), AC(University of Illinois System), AD(University of New Mexico), AE(University of Illinois System) %J AAS/High Energy Astrophysics Division #11 %V 11 %D 03/2010 %P 18.05 %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/2010HEAD...11.1805S %B This paper describes a Chandra observation of the supernova remnant SNR 0540-697 within the HII complex N159 in the Large Magellanic Cloud. Scattering from the nearby bright source LMC X-1, which obscures the western edge of the remnant, has been removed. Larger than previously believed, the 2.0 X 2.8 arcmininute remnant is defined by optical filaments and two lobes of X-ray emission. A band of intervening material absorbs X-rays from the central part of the remnant. The N Lobe of the remnant is relatively bright and well defined, while emission from the S Lobe is much weaker. There is structure within the N Lobe but the outer shell is not prominent in X-rays. The X-ray spectrum is thermal with some emission lines. The derived physical parameters of this SNR are consistent with those expected for older remnants.

There is also diffuse thermal X-ray emission north of N159 extending into N160, evidence for a larger remnant or bubble. %R 2009cxo..prop.4168S %T Chandra Supernova Remnant Catalog Update %A Seward, Frederick %J Chandra Proposal %D 09/2009 %P 4168 %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/2009cxo..prop.4168S %X Chandra proposal ID #11500086 %B We seek funds to hire a person to repair and update our web-based catalog of Chandra supernova remnant observations. We have found this quite useful for general-knowledge browsing and for proposal preparation. It is also used by a number of organizations. Eliminating the PI's computer, search engines, and selecting one remnant (so a catalog visit counts as 1) we record about 50-100 hits/month. But after 5 years of use, environment updates and other improvements have broken some of the scripts. Some information is hard to retrieve and catalog updates are now done by hand. There are also research possibilities which could be enhanced. We need someone to concentrate on this for 3-6 months, fix the scripts, and incorporate new material. %R 2008ApJ...676.1040C %T The Thermal Composite Supernova Remnant Kesteven 27 as Viewed by Chandra: Shock Reflection from a Cavity Wall %A Chen, Yang; Seward, Frederick D.; Sun, Ming; Li, Jiang-tao %F AA(Nanjing University, Department of Astronomy), AB(Harvard Smithsonian Center for Astrophysics), AC(Michigan State University, Department of Physics and Astronomy), AD(Nanjing University, Department of Astronomy) %J The Astrophysical Journal %V 676 %D 04/2008 %P 1040 %L 1049 %K ISM: individual: Kesteven 27 = G327.4+0.4, radiation mechanisms: thermal, shock waves, supernova remnants, X-rays: ISM, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I EPRINT_HTML: arXiv Article; %I PUB_HTML: Publisher Article; %I EPRINT_PDF: arXiv PDF; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/2008ApJ...676.1040C %B We present a spatially resolved spectroscopic study of the thermal composite supernova remnant Kes 27 with Chandra. The X-ray spectrum of Kes 27 is characterized by K lines from Mg, Si, S, Ar, and Ca. The X-ray-emitting gas is found to be enriched in sulfur and calcium. The broadband and tricolor images show two incomplete shell-like features in the northeastern half and brightness fading with increasing radius to the southwest. There are over 30 unresolved sources within the remnant. None shows characteristics typical of a young neutron star. The maximum diffuse X-ray intensity coincides with a radio-bright region along the eastern border. In general, gas in the inner region is at higher temperature, and the emission is brighter, than that in the outer region. The gas in the remnant appears to be near ionization equilibrium. The overall morphology can be explained by the evolution of the remnant in an ambient medium with a density enhancement from west to east. We suggest that the remnant was born in a preexisting cavity and that the bright inner emission is due to the reflection of the initial shock from the dense cavity wall. This scenario may provide a new candidate mechanism to explain the X-ray morphology of other thermal composite supernova remnants. %H IOP %Y DOI: 10.1086/525240 %Y eprintid: arXiv:0711.0515 %R 2007ApJ...665.1304H %T X-Ray Timing of PSR J1852+0040 in Kesteven 79: Evidence of Neutron Stars Weakly Magnetized at Birth %A Halpern, J. P.; Gotthelf, E. V.; Camilo, F.; Seward, F. D. %F AA(Columbia University, Department of Astronomy and Astrophysics), AB(Columbia University, Department of Astronomy and Astrophysics), AC(Columbia University, Department of Astronomy and Astrophysics), AD(Smithsonian Astrophysical Observatory) %J The Astrophysical Journal %V 665 %D 08/2007 %P 1304 %L 1310 %K ISM: Individual: Name: Kesteven 79, ISM: Individual: Alphanumeric: SN 1987A, Stars: Pulsars: Individual: Alphanumeric: 1E 1207.4-5209, pulsars: individual (CXOU J185238.6 + 004020), pulsars: individual (PSR J1852 + 0040), Stars: Neutron, ISM: Supernova Remnants, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I EPRINT_HTML: arXiv Article; %I PUB_HTML: Publisher Article; %I EPRINT_PDF: arXiv PDF; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %I MAST: Mikulski Archive for Space Telescopes; %I HEASARC: NASA's High Energy Astrophysics Science Archive Research Center; %I XMM: XMM Newton Science Archive; %U https://ui.adsabs.harvard.edu/abs/2007ApJ...665.1304H %B The 105 ms X-ray pulsar J1852+0040 is the central compact object (CCO) in supernova remnant Kes 79. We report a sensitive upper limit on its radio flux density of 12 μJy at 2 GHz using the NRAO Green Bank Telescope. Timing using the Newton X-Ray Multi-Mirror Mission (XMM-Newton) and the Chandra X-Ray Observatory over a 2.4 yr span reveals no significant change in its spin period. The 2 σ upper limit on the period derivative leads, in the dipole spin-down formalism, to an energy loss rate E˙<7×10³³ ergs s^-1, surface magnetic field strength B_p<1.5×10¹¹ G, and characteristic age τ_c≡P/2P˙>8 Myr. This value of τ_c exceeds the age of the SNR by 3 orders of magnitude, implying that the pulsar was born spinning at its current period. However, the X-ray luminosity of L_bol~3×10³³(d/7.1 kpc)² ergs s^-1 is a large fraction of E˙, which challenges the rotation-powered assumption. Instead, its high blackbody temperature kT_BB=0.46+/-0.04 keV, small blackbody radius R_BB~0.8 km, and large pulsed fraction f_p~80% may be evidence of accretion onto a polar cap, possibly from a fallback disk made of supernova debris. If B_p<10¹⁰ G, an accretion disk can penetrate the light cylinder and interact with the magnetosphere, while resulting torques on the neutron star remain within the observed limits. A weak B field is also inferred in another CCO, the 424 ms pulsar, from its steady spin and soft X-ray absorption lines. We propose this origin of radio-quiet CCOs: the magnetic field, derived from a turbulent dynamo, is weaker if the neutron star is formed spinning slowly, which enables it to accrete supernova debris. Accretion excludes neutron stars born with both B_p<10¹¹ G and P>0.1 s from radio pulsar surveys, where B_p<10¹¹ G is not encountered except among very old (τ_c>40 Myr) or recycled pulsars. Finally, such a CCO, if born in SN 1987A, could explain the nondetection of a pulsar there. %H IOP %Y DOI: 10.1086/519557 %Y eprintid: arXiv:0705.0978 %R 2006ApJ...652.1277S %T Faint X-Ray Structure in the Crab Pulsar Wind Nebula %A Seward, F. D.; Tucker, W. H.; Fesen, R. A. %F AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory), AC(Dartmouth College, Department of Physics and Astronomy) %J The Astrophysical Journal %V 652 %D 12/2006 %P 1277 %L 1287 %K ISM: Individual: Name: Crab Nebula, Stars: Neutron, ISM: Supernova Remnants, X-Rays: ISM, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I EPRINT_HTML: arXiv Article; %I PUB_HTML: Publisher Article; %I EPRINT_PDF: arXiv PDF; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/2006ApJ...652.1277S %B We report on a Chandra observation of the Crab Nebula that gives the first clear view of the faint boundary of the Crab's X-ray-emitting pulsar wind nebula. There is structure in all directions. Fingers, loops, bays, and the south pulsar jet all indicate that either filamentary material or the magnetic field is controlling the relativistic electrons. In general, spectra soften as distance from the pulsar increases but do not change rapidly along linear features. This is particularly true for the pulsar jet. The termination of the jet is abrupt; the east side is close to an [O III] optical filament, which may be blocking propagation on this side. We argue that linear features have ordered magnetic fields and that the structure is determined by the synchrotron lifetime of particles diffusing perpendicular and parallel to the magnetic field. We find no significant evidence for thermal X-rays inside the filamentary envelope. %H IOP %Y DOI: 10.1086/508532 %Y eprintid: arXiv:astro-ph/0608485 %R 2006cxo..prop.2270S %T Accurate Determination of the Dust-Scattering Halo Around Cyg X-2 %A Seward, Frederick %J Chandra Proposal %D 09/2006 %P 2270 %K Chandra Proposal ID #08910231 %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/2006cxo..prop.2270S %B In a short time, one million events can be collected from the bright dust-scattered halo around CYG X-2. The ACIS observation is the first serious attempt to observe azimuthal structure in a dust-scattering halo. If structure due to nonuniformity of the gas and dust permits, we will measure the quadrupole moment of the halo which might indicate scattering from partially-aligned non-spherical grains in the path to the source. Systematic instrument effects will be identified by observing at different roll angles. We will also extract the radial dependence of surface brightness from 5" to 15' in several energy bands and use these data to investigate the applicability of several dust models. Model parameters will be derived concerning size and spatial distribution of dust particles. %R 2006ApJ...640..327S %T Chandra Observation of the Magellanic Cloud Supernova Remnant 0454-67.2 in N9 %A Seward, F. D.; Williams, R. M.; Chu, Y. -H.; Dickel, J. R.; Smith, R. C.; Points, S. D. %F AA(Smithsonian Astrophysical Observatory), AB(University of Illinois, Urbana-Champaign), AC(University of Illinois, Urbana-Champaign), AD(University of Illinois, Urbana-Champaign), AE(Cerro Tololo Interamerican Observatory), AF(Cerro Tololo Interamerican Observatory) %J The Astrophysical Journal %V 640 %D 03/2006 %P 327 %L 334 %K ISM: individual (SNR 0454-67.2), ISM: Supernova Remnants, X-Rays: ISM, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I EPRINT_HTML: arXiv Article; %I PUB_HTML: Publisher Article; %I EPRINT_PDF: arXiv PDF; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %U https://ui.adsabs.harvard.edu/abs/2006ApJ...640..327S %B A Chandra observation has defined the extent of the SNR 0454-67.2 in the LMC H II region N9. The remnant has dimension 2.3 arcmin×3.6 arcmin and is elongated in the north-south direction. The brightest emission comes from a north-south central ridge that includes three bright patches. There is good agreement between X-ray and [O III] and [S II] morphology. The remnant is old enough so that optical data give more information about dynamics than do the X-ray data. The supernova (SN) energy release was >=5×10⁵⁰ ergs, and the age is ~3×10⁴ yr. There are several unresolved sources nearby, but none are clearly associated with the remnant. The X-ray spectrum is soft and indicates enhanced Fe abundance in the central region, consistent with a Type Ia SN origin, but a Type II origin cannot be ruled out. %H IOP %Y DOI: 10.1086/499767 %Y eprintid: arXiv:astro-ph/0511619 %R 2006ApJ...636..873S %T Chandra Observations of the X-Ray Halo around the Crab Nebula %A Seward, F. D.; Gorenstein, P.; Smith, R. K. %F AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory), AC(NASA Goddard Space Flight Center, Maryland; Johns Hopkins University, Department of Physics and Astronomy) %J The Astrophysical Journal %V 636 %D 01/2006 %P 873 %L 880 %K ISM: Individual: Name: Crab Nebula, ISM: Supernova Remnants, X-Rays: ISM, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I EPRINT_HTML: arXiv Article; %I PUB_HTML: Publisher Article; %I EPRINT_PDF: arXiv PDF; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/2006ApJ...636..873S %B Two Chandra observations have been used to search for thermal X-ray emission from within and around the Crab Nebula. Dead time was minimized by excluding the brightest part of the nebula from the field of view. A dust-scattered halo comprising 5% of the strength of the Crab is clearly detected, with surface brightness measured out to a radial distance of 18'. Coverage is 100% at 4', 50% at 12', and 25% at 18'. The observed halo is compared with predictions based on three different interstellar grain models, and one can be adjusted to fit the observation. This dust halo and mirror scattering form a high background region that has been searched for emission from shock-heated material in an outer shell. We find no evidence for such emission. We can set upper limits a factor of 10-1000 less than the surface brightness observed from outer shells around similar remnants. The upper limit for X-ray luminosity of an outer shell is ~10³⁴ ergs s^-1. Although it is possible to reconcile our observation with an 8-13 M_solar progenitor, we argue that this is unlikely. %H IOP %Y DOI: 10.1086/498105 %Y eprintid: arXiv:astro-ph/0509636 %R 2006ESASP.604..375W %T New High Resolution X-ray Studies of Magellanic Cloud Supernova Remnants %A Williams, R. N. M.; Chu, Y. -H.; Chen, C. -H.; Gruendl, R. A.; Dickel, J. R.; Seward, F. D.; Guerrero, M. A.; Shelton, R.; MCELS Collaboration %J The X-ray Universe 2005 %V 604 %D 01/2006 %P 375 %I CITATIONS: Citations to the Article; %I TOC: Table of Contents; %I ADS_SCAN: Scanned Article (GIF); %I PUB_PDF: Publisher PDF; %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/2006ESASP.604..375W %R 2006cosp...36.3449C %T Chandra spectroscopy of thermal composite supernova remnant Kes 27 %A Chen, Yang; Seward, F. D.; Sun, Ming; Li, J. -T. %J 36th COSPAR Scientific Assembly %V 36 %D 01/2006 %P 3449 %I ABSTRACT: Abstract; %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/2006cosp...36.3449C %B We present a spatially resolved spectroscopic study of thermal composite supernova remnant Kes 27 with sl Chandra ACIS observation The X-ray spectrum of Kes 27 is characterized by evident K lines from element species Mg Si S Ar and Ca Most of the X-ray emitting regions are found to be silicon-enriched Calcium is also over-abundant in the remnant The broadband and tri-color images of the remnant show two incomplete shell-like features in the northeastern half and brightness fading away with radius in the southwest The X-ray intensity peak coincides with the radio bright region along the eastern border The gas in the inner region is at higher temperature and emits brighter and harder emission than that in the outer The gas in the remnant is generally close to ionization equilibrium The overall morphology can be explained by the evolution of the remnant in an ambient medium with a density gradient from west to the east We discuss the effect of reflected reverse shock and cloud evaporation the mechanisms that may cause the inner bright emission There are no unresolved sources that might be a central compact object %R 2005ApJ...633..946K %T Chandra Observations of the W51C Supernova Remnant %A Koo, Bon-Chul; Lee, Jae-Joon; Seward, Frederick D.; Moon, Dae-Sik %F AA(Seoul National University, Department of Physics and Astronomy; JAXA, Institute of Space and Astronautical Science), AB(Seoul National University, Department of Physics and Astronomy), AC(Harvard Smithsonian Center for Astrophysics), AD(California Institute of Technology, Division of Physics, Mathematics and Astronomy) %J The Astrophysical Journal %V 633 %D 11/2005 %P 946 %L 952 %K ISM: Individual: Alphanumeric: W51, ISM: Supernova Remnants, X-Rays: ISM %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I PUB_HTML: Publisher Article; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/2005ApJ...633..946K %B We present the results of Chandra ACIS observations of the supernova remnant (SNR) W51C. The remnant is located in the cross section of the Sagittarius arm, and the Chandra images present a superb X-ray view of this complex region including the massive star-forming region W51B. The properties of thermal diffuse SNR emission are consistent with the results of previous studies except that an enhanced abundance of sulfur is required. It is found that the ASCA hard X-ray source CXO J192318.5+1403035, proposed to be a pulsar wind nebula, is composed of a relatively bright core surrounded by an extended (~7.0×2.5 pc) diffuse envelope. The core contains a compact (<0.1 pc) source at the center. The X-ray spectrum of CXO J192318.5+1403035 can be fitted by a power-law emission model with Γ=1.82^+0.28_-0.29, and the implied X-ray (0.2-4.0 keV) luminosity is 5×10³³ ergs s^-1. The core contributes ~20% of the total luminosity. The core-envelope structure and its spectral properties support CXO J192318.5+140305 as a pulsar-wind nebula associated with the SNR W51C. There is also enhanced radio emission coincident with the source. It is conceivable that the central compact source might harbor a pulsar. However, the large extent and the hardening of X-rays at the extreme boundaries need to be explained. We have searched for the Brγ line from the ionized gas associated with the source, but no emission was detected. %H IOP %Y DOI: 10.1086/491468 %R 2005JRASC..99R.136E %T Chandra Observations of Open Cluster h Per %A Evans, N. R.; Wolk, S.; Bizunok, N.; Spitzbart, B.; Seward, F.; Kenyon, S.; Barnes, T.; Pasachoff, J. M. %J Journal of the Royal Astronomical Society of Canada %V 99 %D 08/2005 %P 136 %I ABSTRACT: Abstract; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/2005JRASC..99R.136E %B We have obtained a 40 ksec ACIS observation of the open star cluster h Per in December 2004, from which we have identified more than 200 X-ray sources and found optical counterparts for many of them. We are processing the h Per data with the ANCHORS pipeline, which is being used to process Chandra observations of star forming regions in a uniform manner. This will provide fits to the instrumental low-resolution spectra for cool pre-main sequence stars in h Per including fluxes, temperatures, and absorption. %R 2005ApJ...628..704W %T Supernova Remnants in the Magellanic Clouds. V. The Complex Interior Structure of the N206 Supernova Remnant %A Williams, R. M.; Chu, Y. -H.; Dickel, J. R.; Gruendl, R. A.; Seward, F. D.; Guerrero, M. A.; Hobbs, G. %F AA(University of Illinois, Urbana-Champaign, Department of Astronomy), AB(University of Illinois, Urbana-Champaign, Department of Astronomy), AC(University of Illinois, Urbana-Champaign, Department of Astronomy), AD(University of Illinois, Urbana-Champaign, Department of Astronomy), AE(Harvard Smithsonian Center for Astrophysics), AF(Institute of Astrophysics of Andalusia), AG(CSIRO Australian Telescope National Facility) %J The Astrophysical Journal %V 628 %D 08/2005 %P 704 %L 720 %K ISM: Individual: Alphanumeric: SNR B0532-71.0, Galaxies: Magellanic Clouds, X-Rays: ISM, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I EPRINT_HTML: arXiv Article; %I PUB_HTML: Publisher Article; %I EPRINT_PDF: arXiv PDF; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %I MAST: Mikulski Archive for Space Telescopes; %I ESA: ESAC Science Data Center; %I XMM: XMM Newton Science Archive; %U https://ui.adsabs.harvard.edu/abs/2005ApJ...628..704W %B The N206 supernova remnant (SNR) in the Large Magellanic Cloud has long been considered a prototypical ``mixed morphology'' SNR. Recent observations, however, have added a new twist to this familiar plot: an elongated, radially oriented radio feature seen in projection against the SNR face. Utilizing the high resolution and sensitivity available with the Hubble Space Telescope, Chandra, and XMM-Newton, we have obtained optical emission line images and spatially resolved X-ray spectral maps for this intriguing SNR. Our findings present the SNR itself as a remnant in the middle to late stages of its evolution. X-ray emission associated with the radio linear feature strongly suggests it to be a pulsar wind nebula (PWN). A small X-ray knot is discovered at the outer tip of this feature. The feature's elongated morphology and the surrounding wedge-shaped X-ray enhancement strongly suggest a bow shock PWN structure. %H IOP %Y DOI: 10.1086/431349 %Y eprintid: arXiv:astro-ph/0504609 %R 2005JRASC..99..136E %T Chandra observations of open cluster h Per. %A Evans, N. R.; Wolk, S.; Bizunok, N.; Spitzbart, B.; Seward, F.; Kenyon, S.; Barnes, T.; Pasachoff, J. M. %J Journal of the Royal Astronomical Society of Canada %V 99 %D 08/2005 %P 136 %L 137 %I ABSTRACT: Abstract; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/2005JRASC..99..136E %B We have obtained a 40 ksec ACIS observation of the open star cluster h Per in December, 2004, from which we have identified more than 200 X-ray sources and found optical counterparts for many of them. We are processing the h Per data with the ANCHORS pipeline which is being used to process Chandra observations of star forming regions in a uniform manner. This will provide fits to the instrumental low resolution spectra for cool pre-main sequence stars in h Per including fluxes, temperatures and absorption. %R 2005sfet.confE..48B %T h Persei: Young Star Cluster in X-rays %A Bizunok, Natalya; Wolk, S. J.; Evans, N. R.; Spitzbart, B.; Seward, F.; Kenyon, S.; Barnes, T.; Pasachoff, J. M. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics), AE(Harvard Smithsonian Center for Astrophysics), AF(Harvard Smithsonian Center for Astrophysics), AG(University of Texas System), AH(Williams College) %J Star Formation in the Era of Three Great Observatories %D 07/2005 %P 48 %I ABSTRACT: Abstract; %I TOC: Table of Contents; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/2005sfet.confE..48B %B We have obtained a 40 ksec ACIS observation of the open star cluster h Per in December, 2004, from which we have identified more than 200 X-ray sources and found optical counterparts for many of them. We are processing the h Per data with the ANCHORS pipeline, which is being used to process Chandra observations of star forming regions in a uniform manner. This will provide fits to the instrumental low-resolution spectra for cool pre-main sequence stars in h Per including fluxes, temperatures, and absorptions. %R 2005ApJ...627..390G %T Discovery of a 105 ms X-Ray Pulsar in Kesteven 79: On the Nature of Compact Central Objects in Supernova Remnants %A Gotthelf, E. V.; Halpern, J. P.; Seward, F. D. %F AA(Columbia University, Department of Astronomy and Astrophysics), AB(Columbia University, Department of Astronomy and Astrophysics), AC(Smithsonian Astrophysical Observatory) %J The Astrophysical Journal %V 627 %D 07/2005 %P 390 %L 396 %K ISM: Individual: Name: Kesteven 79, Stars: Pulsars: Individual: Alphanumeric: CXOU J185238.6+004020, Stars: Pulsars: Individual: Alphanumeric: PSR J1852+0040, Stars: Neutron, ISM: Supernova Remnants, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I EPRINT_HTML: arXiv Article; %I PUB_HTML: Publisher Article; %I EPRINT_PDF: arXiv PDF; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %I XMM: XMM Newton Science Archive; %U https://ui.adsabs.harvard.edu/abs/2005ApJ...627..390G %B We report the discovery of 105 ms X-ray pulsations from the compact central object (CCO) in the supernova remnant Kes 79 using data acquired with the Newton X-Ray Multi-Mirror Mission (XMM-Newton). Two observations of the pulsar taken 6 days apart yield an upper limit on its spin-down rate of P˙<7×10^-14 s s^-1 and no evidence for binary orbital motion. The implied energy loss rate is E˙<2×10³⁶ ergs s^-1, the surface magnetic field strength is B_p<3×10¹² G, and the spin-down age is τ>24 kyr. The latter exceeds the remnant's estimated age, suggesting that the pulsar was born spinning near its current period. The X-ray spectrum of PSR J1852+0040 is best characterized by a blackbody model of temperature kT_BB=0.44+/-0.03 keV, radius R_BB~0.9 km, and L_bol=3.7×10³³ ergs s^-1 at d=7.1 kpc. The sinusoidal light curve is modulated with a pulsed fraction of >45%, suggestive of a small hot spot on the surface of the rotating neutron star. The lack of a discernible pulsar wind nebula is consistent with an interpretation of PSR J1852+0040 as a rotation-powered pulsar whose spin-down luminosity falls below the empirical threshold for generating bright wind nebulae, E˙_c~4×10³⁶ ergs s^-1. The age discrepancy implies that its E˙ has always been below E˙_c, perhaps a distinguishing property of the CCOs. Alternatively, the X-ray spectrum of PSR J1852+0040 suggests a low-luminosity anomalous X-ray pulsar (AXP), but the weak inferred B_p field is incompatible with a magnetar theory of its X-ray luminosity. We cannot exclude accretion from a fallback disk. The ordinary spin parameters discovered from PSR J1852+0040 highlight the difficulty that existing theories of isolated neutron stars have in explaining the high luminosities and temperatures of CCO thermal X-ray spectra. %H IOP %Y DOI: 10.1086/430300 %Y eprintid: arXiv:astro-ph/0503424 %R 2005yCat.9002....0C %T VizieR Online Data Catalog: Second Ariel X-Ray Catalogue (2A) (Cooke+ 1978) %A Cooke, B. A.; Ricketts, M. J.; Maccacaro, T.; Pye, J. P.; Elvis, M.; Watson, M. G.; Griffiths, R. E.; Pounds, K. A.; McHardy, I. M.; Maccagni, D.; Seward, F. D.; Page, C. G.; Turner, M. J. L. %J VizieR Online Data Catalog %V 9002 %D 05/2005 %P IX/2 %K X-ray sources %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/2005yCat.9002....0C %X 2a.dat 107x80 Catalog Data (table1, plus 2 additional sources); doc.txt 280x79 Original ADC documentation %B This catalog contains 107 sources in the energy range 2-18 keV, galactic latitude |b|>10°. It results from the sky survey conducted by the Leiscester Sky Survey Instrument on Ariel V.

The file "2a.dat" is the electronic version of the table 1 of the original paper, prepared by G. Share (Naval Research Laboratory). It contains 2 sources more than the original paper.

(2 data files). %R 2005AAS...206.3604B %T The Open Cluster h Per as Seen by Chandra %A Bizunok, N. S.; Evans, N. R.; Wolk, S. J.; Spitzbart, B.; Seward, F. D.; Kenyon, S. J.; Barnes, T. G.; Pasachoff, J. M. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics), AE(Harvard Smithsonian Center for Astrophysics), AF(Harvard Smithsonian Center for Astrophysics), AG(University of Texas System), AH(Williams College) %J American Astronomical Society Meeting Abstracts #206 %V 206 %D 05/2005 %P 36.04 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/2005AAS...206.3604B %B In December, 2004, we observed the open star cluster h Per with Chandra ACIS for 40 ksec. We have identified more than 200 X-ray sources on the image and found optical counterparts for many of them. The ANCHORS pipeline, which we used to process the data, provides homogeneous output products for this and many other star forming regions. Among the outputs are fits to the instrumental low resolution spectra for cool pre-main sequence stars in h Per that yield flux, temperature and absorption for these sources.

Funding for this investigation has been provided by Chandra contract NAS8-39073 and NASA Grant GO5-6007A %R 2005xrrc.procE6.04S %T How to Write an X-ray Proposal %A Seward, F. D. %F AA(Smithsonian Astrophysical Observatory) %J X-Ray and Radio Connections %D 04/2005 %P 6.04 %K X-ray, radio, proposals %I ABSTRACT: Abstract; %I TOC: Table of Contents; %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/2005xrrc.procE6.04S %B The Chandra observing proposal process is described. Suggestions are given to minimize the pain of proposal submission and to maximize the chance of getting observing time. %R 2005ChNew..12....1C %T Unveiling Eta Carinae with Chandra %A Corcoran, M. F.; Seward, F. D.; Henley, D. B.; Hamaguchi, K. %F AA(Universities Space Research Association), AB(Smithsonian Astrophysical Observatory), AC(University of Birmingham, UK), AD(NRC) %J Chandra News %V 12 %D 01/2005 %P 1 %L 5 %U https://ui.adsabs.harvard.edu/abs/2005ChNew..12....1C %R 2005ChNew..12...29S %T How to Write an X-ray Proposal %A Seward, Fred %J Chandra News %V 12 %D 01/2005 %P 29 %L 30 %U https://ui.adsabs.harvard.edu/abs/2005ChNew..12...29S %R 2004AAS...205.7005W %T The Supernova Remnant and Superbubble Components of the N206 Complex %A Williams, R. N. M.; Chu, Y. -H.; Dickel, J. R.; Gruendl, R. A.; Dunne, B. C.; Guerrero, M. A.; Seward, F. D.; Hobbs, G.; Magellanic Cloud Emission-Line Survey %F AA(University of Illinois System), AB(University of Illinois System), AC(University of Illinois System), AD(University of Illinois System), AE(University of Illinois System), AF(Institute of Astrophysics of Andalusia), AG(Harvard Smithsonian Center for Astrophysics), AH(CSIRO Australian Telescope National Facility) %J American Astronomical Society Meeting Abstracts %V 205 %D 12/2004 %P 70.05 %I ABSTRACT: Abstract; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/2004AAS...205.7005W %B Supernovae (SNe), through their diffuse supernova remnants (SNRs), are primarily responsible for the injection of energy and heavy elements into the interstellar medium (ISM). The consequences of these injections are far-reaching. SNe provide most of the hot gas component of the ISM, and through collective inputs to structures such as superbubbles (SBs), can transfer hot gas into a galaxy halo. The energy and heavy elements influence future generations of star formation in a galaxy and have a profound effect on galaxy evolution.

We have undertaken a large project to examine the dispersal of energy and heavy elements into a host galaxy by its population of SNRs and SBs, using the populations of therse objects in the Large and Small Magellanic Clouds (LMC, SMC). As part of this study, we have examined of the neighboring N206 SNR (SNR B 0532-71.0) and N206 superbubble (DEM L 221) at optical, X-ray and radio wavelengths.

The N206 SNR was recently found to posess an elongated, radially-oriented radio feature. Utilizing the HST, Chandra, and XMM-Newton, we have obtained optical emission-line images and spatially resolved X-ray spectral maps for this SNR. Our findings imply the SNR is in the mid to late stages of its evolution. X-ray emission associated with the radio "linear feature" strongly suggests it to be a pulsar-wind nebula (PWN). A small-diameter X-ray source is discovered at the outer tip of this feature, which, with the feature's elongated morphology, suggests a bow-shock PWN structure.

X-ray emission from the N206 superbubble had been detected with ROSAT. Using the higher sensitivity of XMM, we were able to obtain detailed spectral results for ths SB. We combine this information with ground-based optical emission-line and radio HI data to form a complete picture of this SB and its possible enhancements of X-ray emission from internal SNRs. %R 2004AAS...20510105S %T Chandra Observation of the Magellanic Cloud Supernova Remnant 0454-672 in N9 %A Seward, F. D.; Chu, Y. -H.; Dickel, J. R.; Williams, R. M.; Smith, C. %F AA(Smithsonian Astrophysical Observatory), AB(University of Illinois System), AC(University of Illinois System), AD(University of Illinois System), AE(Cerro Tololo Interamerican Observatory) %J American Astronomical Society Meeting Abstracts %V 205 %D 12/2004 %P 101.05 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/2004AAS...20510105S %B A Chandra observation has defined the extent of a supernova remnant in the LMC HII region N9. There is good agreement between X-ray and OIII and SII morphology. In X-rays, the central region is bright and emission from the outer shell is weak. The X-ray spectrum is soft and indicates enhanced Fe abundance in the central region which favors a Type IA SN origin. %R 2004ApJ...612.1065E %T Chandra Observations of Associates of η Carinae. II. Spectra %A Evans, Nancy Remage; Schlegel, Eric M.; Waldron, Wayne L.; Seward, Frederick D.; Krauss, Miriam I.; Nichols, Joy; Wolk, Scott J. %F AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory), AC(L-3 Communications Government Services, Inc., 1801 McCormick Drive, Suite 170, Largo, MD 20774), AD(Smithsonian Astrophysical Observatory), AE(Smithsonian Astrophysical Observatory), AF(Smithsonian Astrophysical Observatory), AG(Smithsonian Astrophysical Observatory) %J The Astrophysical Journal %V 612 %D 09/2004 %P 1065 %L 1080 %K Stars: Individual: Constellation Name: η Carinae, X-Rays: Stars, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I EPRINT_HTML: arXiv Article; %I PUB_HTML: Publisher Article; %I EPRINT_PDF: arXiv PDF; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/2004ApJ...612.1065E %B The low-resolution X-ray spectra around η Car covering Trumpler 16 and part of Trumpler 14 have been extracted from a Chandra CCD ACIS image. Various analysis techniques have been applied to the spectra based on their count rates. The spectra with the greatest number of counts (HD 93162 = WR 25, HD 93129 AB, and HD 93250) have been fitted with a wind model, which uses several components with different temperatures and depths in the wind. Weaker spectra have been fitted with Raymond-Smith models. The weakest spectra are simply intercompared with strong spectra. In general, fits produce reasonable parameters based on knowledge of the extinction from optical studies and on the range of temperatures for high- and low-mass stars. Direct comparisons of spectra confirm the consistency of the fitting results and also hardness ratios for cases of unusually large extinction in the clusters. The spectra of the low-mass stars are harder than the more massive stars. Stars in the sequence evolving from the main sequence (HD 93250) through the system containing the O supergiant (HD 93129 AB) and then through the Wolf-Rayet stage (HD 93162), presumably ending in the extreme example of η Car, share the property of being unusually luminous and hard in X-rays. For these X-ray-luminous stars, their high mass and evolutionary status (from the very last stages of the main sequence and beyond) is the common feature. Their binary status is mixed, and their magnetic status is still uncertain.

Based on observations made with the Chandra X-Ray Observatory. %H IOP %Y DOI: 10.1086/422543 %Y eprintid: arXiv:astro-ph/0405587 %R 2004HEAD....8.2806S %T Search for Thermal X-rays from the Crab Nebula %A Seward, F. D.; Gorenstein, P.; Slane, P. O.; Tucker, W. H.; Smith, R.; Fesen, R. A. %F AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory), AC(Smithsonian Astrophysical Observatory), AD(Smithsonian Astrophysical Observatory), AE(NASA Goddard Space Flight Center, Maryland), AF(Dartmouth College, New Hampshire) %J AAS/High Energy Astrophysics Division #8 %V 8 %D 08/2004 %P 28.06 %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/2004HEAD....8.2806S %B Using two Chandra observations, we have searched for an "outer shell"around the Crab Nebula. Although coverage is not 100 Crab Pulsar (corresponding to an average shock velocity of 11,000 km/s). The observed Nebula is surrounded by a bright X-ray halo due to scattering from the Chandra mirrors and from interstellar dust. No evidence for a blast wave or shock-related X-ray emission is found in this halo. Upper limits for the brightness of an outer shell are derived.

One pointing mapped the faint outer extent of the X-ray synchrotron nebula (or PWN) inside the optical Crab. The outer part of the PWN contains brush-like fingers, loops, clouds, and the termination of the south on-axis pulsar jet. Morphology and spectra are being studied to determine the nature of these features.

This work was supported by Chandra Grants GO2-3087X and GO4-5059X. %R 2004ApJ...605..742S %T Chandra View of Kesteven 79: A Nearly Isothermal Supernova Remnant with Rich Spatial Structure %A Sun, M.; Seward, F. D.; Smith, R. K.; Slane, P. O. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics) %J The Astrophysical Journal %V 605 %D 04/2004 %P 742 %L 750 %K Conduction, ISM: Individual: Name: Kesteven 79, Stars: Winds, Outflows, ISM: Supernova Remnants, X-Rays: ISM, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I EPRINT_HTML: arXiv Article; %I PUB_HTML: Publisher Article; %I EPRINT_PDF: arXiv PDF; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/2004ApJ...605..742S %B A 30 ks Chandra ACIS-I observation of Kes 79 reveals rich spatial structures, including many filaments, three partial shells, a loop, and a ``protrusion.'' Most of them have corresponding radio features. Regardless of the different results from two nonequilibrium ionization (NEI) codes, temperatures of different parts of the remnant are all around 0.7 keV, which is surprisingly constant for a remnant with such rich structure. If thermal conduction is responsible for smoothing the temperature gradient, a lower limit on the thermal conductivity of ~1/10 of the Spitzer value can be derived. Thus, thermal conduction may play an important role in the evolution of at least some supernova remnants (SNRs). No spectral signature of the ejecta is found, which suggests that the ejecta material has been well mixed with the ambient medium. From the morphology and the spectral properties, we suggest that the bright inner shell is a wind-driven shell (WDS) overtaken by the blast wave (the outer shell) and estimate the age of the remnant to be ~6 kyr for the assumed dynamics. Projection is also required to explain the complicated morphology of Kes 79. %H IOP %Y DOI: 10.1086/382666 %Y eprintid: arXiv:astro-ph/0401165 %R 2004ApJ...601.1045S %T X-Ray Observations of the Compact Source in CTA 1 %A Slane, Patrick; Zimmerman, Erik R.; Hughes, John P.; Seward, Frederick D.; Gaensler, Bryan M.; Clarke, Melanie J. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard University, Massachusetts), AC(Rutgers University, Department of Physics and Astronomy), AD(Harvard Smithsonian Center for Astrophysics), AE(Harvard Smithsonian Center for Astrophysics), AF(Harvard Smithsonian Center for Astrophysics) %J The Astrophysical Journal %V 601 %D 02/2004 %P 1045 %L 1049 %K ISM: Individual: Alphanumeric: CTA 1, Stars: Individual: Alphanumeric: RX J0007.0+7302, Stars: Individual: Alphanumeric: 3EG J0010+7309, Stars: Neutron, ISM: Supernova Remnants, X-Rays: ISM, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I EPRINT_HTML: arXiv Article; %I PUB_HTML: Publisher Article; %I EPRINT_PDF: arXiv PDF; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %I HEASARC: NASA's High Energy Astrophysics Science Archive Research Center; %I XMM: XMM Newton Science Archive; %U https://ui.adsabs.harvard.edu/abs/2004ApJ...601.1045S %B We have studied the point source RX J0007.0+7302, at the center of supernova remnant CTA 1, using the X-Ray Multi-mirror Mission (XMM-Newton). The X-ray spectrum of the source is consistent with that of a neutron star and is well described by a power law with the addition of a soft thermal component that may correspond to emission from hot polar cap regions or to cooling emission from a light-element atmosphere over the entire star. There is evidence of extended emission on small spatial scales, which may correspond to structure in the underlying synchrotron nebula. No pulsations are observed. Extrapolation of the nonthermal spectrum of RX J0007.0+7302 to gamma-ray energies yields a flux consistent with that of EGRET source 3EG J0010+7309, supporting the proposition that there is a gamma-ray-emitting pulsar at the center of CTA 1. Observations of the outer regions of CTA 1 with ASCA confirm earlier detections of thermal emission from the supernova remnant and show that the synchrotron nebula extends to the outermost reaches of the remnant. %H IOP %Y DOI: 10.1086/380498 %Y eprintid: arXiv:astro-ph/0310250 %R 2004IAUS..218...93S %T The Chandra Supernova Remnant Catalog %A Seward, F.; Smith, R.; Hagler, J.; Portolese, L.; Gaetz, T.; Slane, P.; Koo, B. -C.; Lee, J. -J. %J Young Neutron Stars and Their Environments %V 218 %D 01/2004 %P 93 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I TOC: Table of Contents; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/2004IAUS..218...93S %B We show some examples from a WWW-based catalog, containing Chandra archive data, that is now under construction. Many remnants show manifestations of internal neutron stars, which are of particular interest to this conference. %R 2003cxo..prop.1451S %T Thermal Emission from the Crab Nebula %A Seward, Frederick %J Chandra Proposal %D 09/2003 %P 1451 %K Chandra Proposal ID #05500128 %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/2003cxo..prop.1451S %B A Cycle 3 observation to search for an outer shock shows nothing outside the visible Crab. There is, however, evidence for soft emission from the northern edge of the 5' X 7' optical nebula, which was just inside the ACIS field of view. This proposal is to observe the entire outer 2' of the 5' X 7' nebula with a sensitivity 10X greater than in previous Chandra observations. It is an exploration of a region not yet really observed (in X-rays) and requires great care to set up so the bright central source does not overwhelm the telemetry. The high spectral resolution of Chandra is essential and the time required modest. The result will be a map of the outer part of the PWN and should also locate additional mass within the Nebula. %R 2003ApJ...589..509E %T Chandra Observations of Associates of η Carinae. I. Luminosities %A Evans, Nancy Remage; Seward, Frederick D.; Krauss, Miriam I.; Isobe, Takashi; Nichols, Joy; Schlegel, Eric M.; Wolk, Scott J. %F AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory), AC(Smithsonian Astrophysical Observatory), AD(Smithsonian Astrophysical Observatory) %J The Astrophysical Journal %V 589 %D 05/2003 %P 509 %L 525 %K Galaxy: Open Clusters and Associations: Individual: Name: Trumpler 14, Galaxy: Open Clusters and Associations: Individual: Name: Trumpler 16, X-Rays: Stars, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I EPRINT_HTML: arXiv Article; %I PUB_HTML: Publisher Article; %I EPRINT_PDF: arXiv PDF; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %I CDS: Strasbourg Astronomical Data Center; %U https://ui.adsabs.harvard.edu/abs/2003ApJ...589..509E %B The region around the η Carinae Nebula has three OB associations, which contain a Wolf-Rayet star and several massive O3 stars. An early Chandra ACIS-I image was centered on η Car and includes Trumpler 16 and part of Trumpler 14. The Chandra image confirms the well-known result that O and very early B stars are X-ray sources with L_X~=10^-7L_bol over an X-ray luminosity range of about 100. Two new, anomalously strong X-ray sources have been found among the hot star population: Tr 16-244, a heavily reddened O3 I star, and Tr 16-22, a heavily reddened O8.5 V star. Two stars have an unusually large L_X/L_bol: HD 93162, a Wolf-Rayet star (and possible binary), and Tr 16-22, a possible colliding-wind binary. In addition, a population of sources associated with cool stars is detected. In the color-magnitude diagram, these X-ray sources sit above the sequence of field stars in the Carina arm. The OB stars are on average more X-ray-luminous than the cool star X-ray sources. X-ray sources among A stars have X-ray luminosities similar to those of cooler stars and may be due to cooler companions. Upper limits are presented for B stars that are not detected in X-rays. These upper limits are also the upper limits for any cool companions that the hot stars may have. Hardness ratios are presented for the most luminous sources in bands 0.5-0.9, 0.9-1.5, and 1.5-2.04 keV. The available information on the binary nature of the hot stars is discussed, but binarity does not correlate with X-ray strength in a simple way.

Based on observations made with the Chandra X-Ray Observatory. %H IOP %Y DOI: 10.1086/374355 %Y eprintid: arXiv:astro-ph/0301485 %R 2003xmm..prop..264S %T XMM-Newton Proposal 02049702 %A Seward, Frederick %J XMM-Newton Proposal %D 03/2003 %P 264 %K CXOUJ185238.6+00402, CXOUJ185238.6+00402, XMM-Newton Proposal 02049702 %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/2003xmm..prop..264S %B We have made a tentative discovery of pulsations from an X-ray source at the center of the Galactic supernova remnant Kes 79. A pointed ROSAT PSPC observation indicates a coherent period with marginal significance, limited only by counting statistics. We propose an EPIC-pn observation to confirm this detection and to obtain a second epoch pulse measurement to determine its spin-down rate. This will allow critical pulsar parameters to be estimated. If the ROSAT period is not confirmed, the request 2 X 21 ks exposures, separated by a week, are sufficient to search independently for the pulsar period and its derivative. Identifying a pulsar at the center of Kes 79 and characterizing its unusual properties have important consequences for neutron star evolution. %R 2003ApJ...584..414S %T A Compact Central Object in the Supernova Remnant Kesteven 79 %A Seward, F. D.; Slane, P. O.; Smith, R. K.; Sun, M. %F AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory), AC(Smithsonian Astrophysical Observatory), AD(Harvard College Observatory) %J The Astrophysical Journal %V 584 %D 02/2003 %P 414 %L 417 %K ISM: Individual: Name: Kesteven 79, Stars: Neutron, ISM: Supernova Remnants, X-Rays: Stars, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I EPRINT_HTML: arXiv Article; %I PUB_HTML: Publisher Article; %I EPRINT_PDF: arXiv PDF; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/2003ApJ...584..414S %B A Chandra X-ray observation has detected an unresolved source at the center of the supernova remnant Kes 79. The best single-model fit to the source spectrum is a blackbody with an X-ray luminosity of L_X(0.3-8.0keV)=7×10³³ ergs s^-1. There is no evidence for a surrounding pulsar wind nebula. There are no cataloged counterparts at other wavelengths, but the absorption is high. The source properties are similar to the central source in Cas A even though the Kes 79 remnant is considerably older. %H IOP %Y DOI: 10.1086/345600 %Y eprintid: arXiv:astro-ph/0210496 %R 2002cxo..prop.1208S %T Observing the Thermal Composite SNR Kes 27 %A Seward, Frederick %J Chandra Proposal %D 09/2002 %P 1208 %K Chandra Proposal ID #04500364 %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/2002cxo..prop.1208S %B An AO-2 ACIS-I observation of Kes 79 has yielded some unexpected results, including a central point source with AXP-like spectrum and many filaments possibly caused by shock-cloud interaction. We propose a 40 ksec ACIS-I observation to a similar SNR to Kes 79: Kes 27. Kes 27 is a thermal composite SNR with a number of unusual properties: one of the youngest thermal composites, the least swept-up mass, limb-brightening at the east and a hard tail above 5 keV. Two point sources revealed by ROSAT inside the remnant can be candidates for a central pulsar. With the proposed observation, we will be able to identify an interior pulsar with any associated nebula, resolve fine structures like filaments, understand its center-filled morphology, and locate the hard tail. %R 2002cxo..prop.1206S %T Supernova Remnants in the Magellanic Clouds %A Seward, Frederick %J Chandra Proposal %D 09/2002 %P 1206 %K Chandra Proposal ID #04500278 %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/2002cxo..prop.1206S %B Chandra has now observed 20 of the brightest remnants in the Magellanic Clouds. Because the distances are known and the absorption low, this set is going to yield definitive data on remnant characteristics and evolution. We propose to observe 6 more remnants in the LMC. All are fainter and some are larger than those in the observed sample. We expect to see faint central sources and previously unobserved structure. These observations will span a region of parameter space not covered in the presently-observed sample aad will include some remnants with unique interesting features. %R 2002AAS...200.7412E %T Associates of Eta Car: New Insights %A Evans, N. R.; Seward, F. D.; Krauss, M. I.; Nichols, J.; Schlegel, E. M.; Wolk, S. J.; Waldron, W. L. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics), AE(Harvard Smithsonian Center for Astrophysics), AF(Harvard Smithsonian Center for Astrophysics), AG(L-3 Comm. Analytics) %J American Astronomical Society Meeting Abstracts #200 %V 200 %D 05/2002 %P 74.12 %I ABSTRACT: Abstract; %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/2002AAS...200.7412E %B The region around the η Car nebula contains several of the most massive stars known (O3 V stars). In addition it also contains objects which (probably) spell out an evolutionary progression from massive (O3 If) supergiants (HD 93129AB, Tr 16-244) to a WN6 Wolf-Rayet star (WR 25 = HD 93162), to η Car itself. We have used a Chandra ACIS-I X-ray image of the region surrounding η Car, including the clusters Tr 16 and Tr 14, to study the stars in this extremely young association. In particular, we discuss modeling of the X-ray spectra of a selection of these objects, together with hardness ratios. We also discuss optical photometry of the newly discovered population of cool star X-ray sources. Supported by funding from Chandra X-ray Center NASA Contract NAS8-39073 %R 2002APS..APRN17036S %T Chandra view of SNR Kes 79 %A Sun, Ming; Seward, Frederick; Smith, Randall; Slane, Patrick %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics) %J APS April Meeting Abstracts %D 04/2002 %P N17.036 %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/2002APS..APRN17036S %B A 30 ks Chandra ACIS-I observation of Kes 79 (G33.6+0.1) provides new insights into this SNR. Spectra from different regions are fitted with several models and results strongly favor an NEI model. This implies underionized states of plasma in Kes 79, which is also indicated by the measured centroids of Mg, Si and S Heα lines. The temperatures in different regions are remarkably similar, around 0.6 keV. The narrow band images of Mg, Si and S also show little difference from one another. A partial shell-like structure is seen between the previously known bright inner and faint outer shells. This might indicate another shell or a projection effect. The X-ray outer shell follows the radio shell very well, including two filamentary structures in the east and a protrusion in the northeast. The thermal structure and evolution of Kes 79 are discussed as well as possibilities for multi-shell structure. %R 2002APS..APRN17035S %T A Central Source in the Supernova Remnant Kes 79 %A Seward, F.; Slane, P.; Smith, R.; Sun, M. %F AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory), AC(Smithsonian Astrophysical Observatory), AD(Smithsonian Astrophysical Observatory) %J APS April Meeting Abstracts %D 04/2002 %P N17.035 %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/2002APS..APRN17035S %B Kes 79 (G33.6+0.1) was observed 31 July 2001 for 30 ks with the Chandra ACIS-I instrument. This remnant, in the constellation Aquila, lies in the galactic plane at a distance of ~10 kpc. The 11^' angular diameter implies an age of a few thousand years. The morphology shows faint outer and bright inner shells. The Chandra image reveals, for the first time, a point-like source at the center of the remnant. This source has a black body spectrum with kT = 0.5 keV. No regular pulsations were found at periods greater than 6.4 s (the ACIS integration time is 3.2 s). No surrounding synchrotron emission wass detected. The X-ray luminosity is 7 × 10^33 erg/s, about 1% the luminosity of the entire remnant. The source may be similar to the one at the center of Cas A. %R 2002ApJ...568..226M %T Discovery of X-Ray Pulsations from the Compact Central Source in the Supernova Remnant 3C 58 %A Murray, Stephen S.; Slane, Patrick O.; Seward, Fredrick D.; Ransom, Scott M.; Gaensler, Bryan M. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics), AE(MIT, Center for Space Research/Kavli Institute) %J The Astrophysical Journal %V 568 %D 03/2002 %P 226 %L 231 %K ISM: Individual: Alphanumeric: 3C 58, Stars: Pulsars: Individual: Alphanumeric: PSR J0205+6449, Stars: Neutron, ISM: Supernova Remnants, X-Rays: Stars, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I EPRINT_HTML: arXiv Article; %I PUB_HTML: Publisher Article; %I EPRINT_PDF: arXiv PDF; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %I HEASARC: NASA's High Energy Astrophysics Science Archive Research Center; %U https://ui.adsabs.harvard.edu/abs/2002ApJ...568..226M %B We report on high time and spatial resolution observations of the supernova remnant (SNR) 3C 58 using the High Resolution Camera (HRC) on the Chandra X-Ray Observatory. These data show a pointlike central source from which we detect 65.68 ms pulsations at 6.7 σ significance. We interpret these pulsations as corresponding to a young rotation-powered pulsar, PSR J0205+6449, that is associated with and powers SNR 3C 58. Analysis of archival Rossi X-Ray Timing Explorer (RXTE) data from 3 years earlier confirms these pulsations and allows us to determine a spin-down rate of P=1.93×10^-13ss^-1. Assuming a magnetic dipole model for PSR J0205+6449, we infer a surface magnetic field of 3.6×10¹² G. The historical age for the pulsar (based on its identification with SN 1181) is 820 yr. Taken with the observed period and spin-down rate, we derive an initial spin period of ~60 ms. %H IOP %Y DOI: 10.1086/338766 %Y eprintid: arXiv:astro-ph/0108489 %R 2002AJ....123.1629K %T An ASCA Study of the W51 Complex %A Koo, Bon-Chul; Lee, Jae-Joon; Seward, Frederick D. %F AA(Seoul National University, Department of Physics and Astronomy), AB(Seoul National University, Department of Physics and Astronomy), AC(Harvard Smithsonian Center for Astrophysics) %J The Astronomical Journal %V 123 %D 03/2002 %P 1629 %L 1638 %K ISM: H II Regions -ISM: Individual: Alphanumeric: W51, Stars: Formation, ISM: Supernova Remnants -X-rays: ISM, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I EPRINT_HTML: arXiv Article; %I PUB_HTML: Publisher Article; %I EPRINT_PDF: arXiv PDF; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %I HEASARC: NASA's High Energy Astrophysics Science Archive Research Center; %U https://ui.adsabs.harvard.edu/abs/2002AJ....123.1629K %B We present the analysis of ASCA archival data from the Galactic source W51. The ASCA spectra show that the soft (kT<~2.5 keV) X-rays are of thermal origin and are compatible with W51C being a single isothermal (kT~=0.3 keV) supernova remnant at the far side of the Sagittarius arm. The ASCA images reveal hard (kT>~2.5 keV) X-ray sources that were not seen in previous X-ray observations. Some of these sources are coincident with massive star-forming regions, and the spectra are used to derive X-ray parameters. By comparing the X-ray-absorbing column density with atomic hydrogen column density, we infer the location of star-forming regions relative to molecular clouds. There are unidentified hard X-ray sources superposed on the supernova remnant, and we discuss the possibility of their association. %H IOP %Y DOI: 10.1086/339179 %Y eprintid: arXiv:astro-ph/0112367 %R 2002cosp...34E2928R %T High-Precision X-ray Timing of the Pulsar in 3C 58 %A Ransom, S.; Kaspi, V.; Gaensler, B.; Murray, S.; Gotthelf, E.; Slane, P.; Seward, F. %J 34th COSPAR Scientific Assembly %V 34 %D 01/2002 %P 2928 %I ABSTRACT: Abstract; %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/2002cosp...34E2928R %B We report results from the first 6 months of X-ray timing of the young pulsar in the supernova remnant 3C 58 using the Rossi X-ray Timing Explorer. In addition to much improved timing parameters, we present high signal-to-noise phase-resolved X-ray spectra, and interpret them in the context of current theories of high energy pulsar emission. %R 2002ASPC..271..270S %T Low-Mass Neutron Stars as Anomalous Pulsars %A Seward, F. D. %J Neutron Stars in Supernova Remnants %V 271 %D 01/2002 %P 270 %K Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I TOC: Table of Contents; %I EPRINT_HTML: arXiv Article; %I ADS_SCAN: Scanned Article (GIF); %I EPRINT_PDF: arXiv PDF; %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/2002ASPC..271..270S %B A neutron star with mass close to the lower limit might be a reasonable model for some anomalous pulsars. Emission is thermal. X-ray luminosity is high. Spatial velocity can be high. Since the radius is predicted to be large, the magnetic field calculated for spin-down is lower than that required by the magnetar model. %Y DOI: 10.48550/arXiv.astro-ph/0112047 %Y eprintid: arXiv:astro-ph/0112047 %R 2001tysc.confE..95E %T Stars Grouped with η Car %A Evans, Nancy Remage; Seward, Fredrick D. %J Two Years of Science with Chandra %D 09/2001 %P 95 %K NORMAL STARS AND WHITE DWARFS %I ABSTRACT: Abstract; %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/2001tysc.confE..95E %B The region around the η Car nebula contains three O associations, which provide examples of very rare objects, including a Wolf-Rayet star and several massive O3 stars. One of the early Chandra ACIS-I images was centered on η Car, and included the region of Trumpler 16 (of which η Car is a member), and also some of Trumpler 14. The Chandra image confirms the well known result that O and very early B stars are X-ray sources (Seward and Chlebowski, 1982, ApJ, 256, 530) with L_X ~= 10^-7 L_bol. In addition, the new Chandra image reveals a population of X-ray sources without O or B spectral type counterparts, which are presumably pre-main sequence stars. Analysis is assisted by reasonable uniformity of the optical extinction across the association. However, X-ray results permit us to confirm extra absorption of soft X-ray flux in two stars which have unusually high optical extinction, and lie near the edge of dust lanes. The energy sensitivity of the ACIS-CCD provides low resolution spectra. We have used these to compare spectra of the stars with different photospheric temperatures, as well as varying stellar wind strengths. %R 2001cxo..prop.3951S %T An Atlas of Chandra Supernova Remnants %A Seward, Frederick %J Chandra Proposal %D 09/2001 %P 3951 %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/2001cxo..prop.3951S %X Chandra proposal ID #03500190 %B We propose to start a catalog of Chandra supernova remnant observations containing images and spectra. We will include images in selected spectral bands and spectra observed from selected parts of the remnants. Tables will give count rates, fluxes, and luminosities. The intent is to present data useful in proposal preparation as well as in studies of properties of remnants as a class of objects. This proposal is to support the incorporation of radio data in the catalog and the development of a website. %R 2001cxo..prop..855S %T Search for the Outer Shell of the Crab Nebula %A Seward, Frederick %J Chandra Proposal %D 09/2001 %P 855 %K Chandra Proposal ID #03500419 %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/2001cxo..prop..855S %B The Crab Nebula is unique among supernova remnants in that there is no evidence for rapidly moving debris from the explosion. We propose to search for an outer shock with sensitivity 10-100 times that of previous X-ray observations. If found, the properties of the shock will determine properties of the progenitor star. Chandra is very well suited for this observation. We will also obtain an excellent image of the dust halo. Properties of the interstellar grains and their distribution can be derived. %R 2001ApJ...553..832S %T Early Chandra X-Ray Observations of η Carinae %A Seward, F. D.; Butt, Y. M.; Karovska, M.; Prestwich, A.; Schlegel, E. M.; Corcoran, M. %F AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory), AC(Smithsonian Astrophysical Observatory), AD(Smithsonian Astrophysical Observatory), AE(Smithsonian Astrophysical Observatory), AF(Goddard Space Flight Center, Astrophysics Division) %J The Astrophysical Journal %V 553 %D 06/2001 %P 832 %L 836 %K Stars: Early-Type, Stars: Individual: Constellation Name: η Carinae, X-Rays: Stars, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I EPRINT_HTML: arXiv Article; %I PUB_HTML: Publisher Article; %I EPRINT_PDF: arXiv PDF; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %I MAST: Mikulski Archive for Space Telescopes; %I ESA: ESAC Science Data Center; %U https://ui.adsabs.harvard.edu/abs/2001ApJ...553..832S %B Subarcsecond-resolution Chandra observations of η Carinae reveal a 40^''×70^'' ring or partial shell of X-ray emission surrounding an unresolved bright central source. The spectrum of the central source is strongly absorbed and can be fitted with a high-temperature thermal continuum and emission lines. The surrounding shell is well outside the optical/infrared bipolar nebula and is coincident with the outer shell of η Car. The X-ray spectrum of the shell is much softer than that of the central source. The X-ray shell is irregular and only correlates well with optical features in which a bright X-ray knot coincides with a bright feature of the outer shell. Implications for the binary model of the central source are discussed. %H IOP %Y DOI: 10.1086/320961 %Y eprintid: arXiv:astro-ph/0101206 %R 2001ApJ...546.1159K %T Chandra Observations of the Young Pulsar PSR B0540-69 %A Kaaret, P.; Marshall, H. L.; Aldcroft, T. L.; Graessle, D. E.; Karovska, M.; Murray, S. S.; Rots, A. H.; Schulz, N. S.; Seward, F. D. %F AA(Harvard Smithsonian Center for Astrophysics), AB(MIT, Center for Space Research/Kavli Institute), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics), AE(Harvard Smithsonian Center for Astrophysics), AF(Harvard Smithsonian Center for Astrophysics), AG(Harvard Smithsonian Center for Astrophysics), AH(MIT, Center for Space Research/Kavli Institute), AI(Harvard Smithsonian Center for Astrophysics) %J The Astrophysical Journal %V 546 %D 01/2001 %P 1159 %L 1167 %K Stars: Pulsars: General, Stars: Pulsars: Individual: Alphanumeric: PSR 0540-69, Stars: Neutron, ISM: Supernova Remnants, X-Rays: Stars, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I EPRINT_HTML: arXiv Article; %I PUB_HTML: Publisher Article; %I EPRINT_PDF: arXiv PDF; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/2001ApJ...546.1159K %B The young pulsar PSR B0540-69 was one of the first targets observed with the Chandra X-Ray Observatory. The high angular resolution of Chandra allows us to resolve the compact nebula surrounding the pulsar. We have determined a position for PSR B0540-69 of R.A.=05^h40^m11.221^s,decl.=- 69^deg19^'54.98" (J2000) with a 1 σ radial uncertainty of 0.7". Combining our measurements of the pulsar period with previous measurements covering a span of 12 years, we derive a braking index of 2.082+/-0.005 (95% confidence). The spectrum of the pulsed emission is consistent with a power law with a photon index of 1.83+/-0.13. The compact nebula has a softer spectrum with a photon index of 1.85-2.26. %H IOP %Y DOI: 10.1086/318287 %Y eprintid: arXiv:astro-ph/0008388 %R 2000cxo..prop..614S %T The Thermal Composite SNR Kes 79 %A Seward, Frederick %J Chandra Proposal %D 09/2000 %P 614 %K Chandra Proposal ID #02500707 %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/2000cxo..prop..614S %B Kes 79 is a relatively young (3-6 kyr) supernova remnant (SNR) with an unusual double-shell X-ray structure. The faint outer shell is aligned with the radio shell, while the bright interior X-rays may form a second shell, although the data are inconclusive. Kes 79 has been classified as a thermal composite remnant due to the thermal X-rays in its interior, but it is very unusual in that an outer shell can also be seen. We propose a 30 ksec ACIS-I observation of Kes 79 to answer these questions about the origin of the interior emission, to map the outer shell and determine its spectrum, and to determine which if any of the competing models for thermal composite remnants fit this unusual object. We will also search for a pulsar with a sensitivity 30 times greater than the existing limit. %R 2000ApJ...538..777E %T Settling onto the Main Sequence: ROSAT Observations of H and χ Persei %A Evans, Nancy Remage; Seward, Fredrick D. %F AA(Smithsonian Astrophysical Observatory) %J The Astrophysical Journal %V 538 %D 08/2000 %P 777 %L 782 %K open clusters and associations: individual (χ Persei, h Persei), Stars: Formation, Stars: Pre-Main-Sequence, X-Rays: Stars %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %I HEASARC: NASA's High Energy Astrophysics Science Archive Research Center; %U https://ui.adsabs.harvard.edu/abs/2000ApJ...538..777E %B We have studied X-rays from the double cluster h and χ Per with an 11 ks ROSAT position-sensitive proportional counter (PSPC) observation. Emission is concentrated toward the two cluster centers. Whether the emission is diffuse emission or from a population of unresolved faint sources is uncertain because the resolution is poor at the distance of the clusters (2.4 kpc). Twenty-three sources were found with an X-ray luminosity of logL=31.5 ergs s^-1 or greater. These sources were found in the cluster nuclei, between the clusters, and in a halo around the cluster pair. The ROSAT PSPC error circle is too large for the identification of X-ray sources with individual optical objects. However, because of a lack of correlation between X-ray sources and B stars, we conclude that the X-rays are produced by late spectral type pre-main-sequence stars. The X-ray sources are brighter than all but the very brightest sources in the younger Orion Nebula cluster, which makes them important in tracing the final stages approaching the main sequence. Based on observations made with the ROSAT satellite. %H IOP %Y DOI: 10.1086/309162 %R 2000ApJ...536..948S %T ROSAT Observations of the Vela Pulsar %A Seward, F. D.; Alpar, M. A.; Flanagan, C.; Kızıloǧlu, Ü.; Markwardt, C.; McCulloch, P.; Ögelman, H. %F AA(Smithsonian Astrophysical Observatory), AB(Sabanci University, Turkey), AC(South African Radio Astronomy Observatory), AD(Sabanci University, Turkey), AE(NASA Goddard Space Flight Center, Maryland), AF(University of Tasmania, School of Mathematics and Physics), AG(University of Wisconsin, Madison, Department of Physics) %J The Astrophysical Journal %V 536 %D 06/2000 %P 948 %L 953 %K Stars: Pulsars: Individual: Name: Vela pulsar, Stars: Neutron, X-Rays: Stars, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I EPRINT_HTML: arXiv Article; %I PUB_HTML: Publisher Article; %I EPRINT_PDF: arXiv PDF; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %I HEASARC: NASA's High Energy Astrophysics Science Archive Research Center; %U https://ui.adsabs.harvard.edu/abs/2000ApJ...536..948S %B The ROSAT HRI was used to monitor X-ray emission from the Vela pulsar. Six observations span 2.5 yr and three glitches. The summed data yield a determination of the pulse shape, and X-ray emission from the pulsar is found to be 12% pulsed with one broad and two narrow peaks. One observation occurred 15 days after a large glitch. No change in pulse structure was observed, and any change in X-ray luminosity, if present, was less than 3%. Implications for neutron star structure are discussed. %H IOP %Y DOI: 10.1086/308961 %Y eprintid: arXiv:astro-ph/0004015 %R 2000ChNew...7....7E %T Chandra Images %A Evans, Nancy Remage; Canizares, Claude; Flanagan, Kathryn; Davis, David; Houck, John; Kraft, Ralph P.; Schwartz, Dan; Murray, Steve; Garcia, Mike; Weisskopf, Martin; Garmire, Gordon; Feigelson, Eric; Broos, Patrick; Hillenbrand, Lynne; Pravdo, Steven; Townsley, Leisa; Tsuboi, Yohko; Seward, Fred; Harnden, Rick; Wolk, Scott %J Chandra News %V 7 %D 05/2000 %P 7 %I PUB_HTML: Publisher Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/2000ChNew...7....7E %R 2000ChNew...7...15S %T Finding Chandra Targets and Target Parameters %A Seward, Fred %J Chandra News %V 7 %D 05/2000 %P 15 %I PUB_HTML: Publisher Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/2000ChNew...7...15S %R 2000ChNew...7...14S %T The Scheduling of Observations %A Seward, Fred %J Chandra News %V 7 %D 05/2000 %P 14 %I PUB_HTML: Publisher Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/2000ChNew...7...14S %R 2000ApJ...533L..29S %T Chandra Observations of the Crab-like Supernova Remnant G21.5-0.9 %A Slane, Patrick; Chen, Yang; Schulz, Norbert S.; Seward, Frederick D.; Hughes, John P.; Gaensler, Bryan M. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics; Nanjing University, Department of Astronomy), AC(MIT, Center for Space Research/Kavli Institute), AD(Harvard Smithsonian Center for Astrophysics), AE(Rutgers University, Department of Physics and Astronomy; CEA Saclay, Service d'Astrophysique), AF(MIT, Center for Space Research/Kavli Institute) %J The Astrophysical Journal %V 533 %D 04/2000 %P L29 %L L32 %K ISM: INDIVIDUAL: ALPHANUMERIC: G21.5-0.9, ISM: SUPERNOVA REMNANTS, X-RAYS: ISM, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I EPRINT_HTML: arXiv Article; %I PUB_HTML: Publisher Article; %I EPRINT_PDF: arXiv PDF; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/2000ApJ...533L..29S %B Chandra observations of the Crab-like supernova remnant G21.5-0.9 reveal a compact central core and spectral variations indicative of synchrotron burn-off of higher energy electrons in the inner nebula. The central core is slightly extended, perhaps indicating the presence of an inner wind-shock nebula surrounding the pulsar. No pulsations are observed from the central region, yielding an upper limit of ~40% for the pulsed fraction. A faint outer shell may be the first evidence of the expanding ejecta and blast wave formed in the initial explosion, indicating a composite nature for G21.5-0.9. %H IOP %Y DOI: 10.1086/312589 %Y eprintid: arXiv:astro-ph/0001536 %R 2000asqu.book..183S %T X-Ray Astronomy %A Seward, Frederick D. %J Allen's Astrophysical Quantities %D 01/2000 %P 183 %I CITATIONS: Citations to the Article; %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/2000asqu.book..183S %R 1999AAS...195.7514S %T Chandra Observation of Eta Carina %A Seward, F. D.; Evans, N. R.; Karovska, M.; Prestwich, A.; Schlegel, E. M.; Corcoran, M.; Townsley, L. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics), AE(Harvard Smithsonian Center for Astrophysics), AF(NASA Goddard Space Flight Center, Maryland), AG(Pennsylvania State University) %J American Astronomical Society Meeting Abstracts %V 195 %D 12/1999 %P 75.14 %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/1999AAS...195.7514S %B A 10 ks observation with the ACIS-I imaging detector reveals a partial, 1' diameter ring of X-ray emission surrounding a central source. The central source is an 8'' diameter region of diffuse emission surrounding a hard unresolved source. All emission from this central region is heavily absorbed, indicating that it originates in the vicinity of the central star(s). The position of the unresolved source is the same as that of the bright central optical object. The outer X-ray ring is of non-uniform brightness and temperature and surrounds the outermost optical nebulosity. An X-ray bright knot is apparently associated with strong N emission in the ``S-Ridge''. The pre-shock velocity implied by the X-ray temperatures and the size of the ring suggests an origin in an event centuries before the ``Great Erruption'' in 1843. X-rays are also detected from nearby early stars. %R 1999ApJ...527..866L %T DA 530: A Supernova Remnant in a Stellar Wind Bubble %A Landecker, T. L.; Routledge, D.; Reynolds, S. P.; Smegal, R. J.; Borkowski, K. J.; Seward, F. D. %F AA(Dominion Radio Astrophysical Observatory), AB(University of Alberta, Canada), AC(North Carolina State University, Department of Physics), AD(University of Alberta, Canada), AE(North Carolina State University, Department of Physics), AF(Harvard Smithsonian Center for Astrophysics) %J The Astrophysical Journal %V 527 %D 12/1999 %P 866 %L 878 %K ISM: BUBBLES, ISM: INDIVIDUAL (DA 530), RADIO CONTINUUM: ISM, ISM: SUPERNOVA REMNANTS, X-RAYS: ISM, ISM: Bubbles, ISM: individual (DA 530), Radio Continuum: ISM, ISM: Supernova Remnants, X-Rays: ISM %C (c) 1999: The American Astronomical Society %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I PUB_HTML: Publisher Article; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %I HEASARC: NASA's High Energy Astrophysics Science Archive Research Center; %U https://ui.adsabs.harvard.edu/abs/1999ApJ...527..866L %B The high-latitude supernova remnant (SNR) DA 530 (G93.3+6.9), apparently a typical shell remnant, has highly polarized radio continuum emission and a very uniform circumferential magnetic field. We present new radio continuum (408 and 1420 MHz) and H I line observations, made with the Dominion Radio Astrophysical Observatory Synthesis Telescope, and we have made the first detection of X-ray emission from the SNR, using the ROSAT Position-Sensitive Proportional Counter. The SNR lies within a shell of H I, possibly created by an earlier stellar wind, whose kinematic distance is nominally 2.5 kpc but whose actual distance may be larger. The X-ray emission is extremely faint. A Raymond-Smith ionization-equilibrium model fits the data and suggests a very low density, ~0.05 cm^-3, consistent with the occurrence of the supernova in a stellar wind cavity, but this model yields an explosion energy 100 times lower than the accepted value. A nonequilibrium shock model, incorporating a range of ionization timescales, is able to give more realistic physical parameters for the supernova remnant. On the balance of the evidence, we place DA 530 at a distance of 3.5 kpc, the largest distance permitted by the H I observations, where it lies 420 pc above the Galactic plane. The explosion, probably a Type Ia supernova, in a low-density cavity has resulted in weak X-ray emission and slow evolution. The explosion energy was 3.9×10⁵⁰ ergs and the age is ~5000 years. The remnant, having swept up 3.9 M_solar in an ambient density of ~0.01 cm^-3, is only now in the adiabatic phase, and this explains the absence of detected optical emission. Despite the low ambient density the efficiency of generation of synchrotron radio emission is ~0.4%, higher than in some historical SNRs. The ratio of radio to X-ray flux is about 100 times that for the remnant of SN 1006, which has comparable radio continuum properties. The very uniform magnetic field is not explained. DA 530 joins a small group of remnants at high Galactic latitude with unusual features, perhaps resulting from low ambient densities. Inhomogeneous nonequilibrium ionization models may be required for the interpretation of the X-ray emission from many other older SNRs. %H IOP %Y DOI: 10.1086/308100 %R 1999yCat..20730781S %T VizieR Online Data Catalog: X-ray observations of galactic Supernova Remnants (Seward, 1990) %A Seward, F. D. %J VizieR Online Data Catalog %V 207 %D 04/1999 %P J/ApJS/73/781 %K Supernova remnants, X-ray sources %I ABSTRACT: Abstract; %I PUB_HTML: Publisher Article; %I CDS: Strasbourg Astronomical Data Center; %U https://ui.adsabs.harvard.edu/abs/1999yCat..20730781S %X snr_ctrt.dat 61x114 SNR Count Rates in Einstein Detectors; snr_indx.dat 76x137 Index to FITS Images of SNR Available on Tape; snr_psrc.dat 62x87 Unresolved X-ray Sources Within or Nearby the SNR %B This paper summarizes the observations of Galactic supernova remnants with the imaging detectors of the Einstein Observatory. X-ray surface brightness contours of 47 remnants are shown together with gray-scale pictures. Count rates for these remnants have been derived and are listed for the HRI, IPC, and MPC detectors. (3 data files). %Y DOI: 10.26093/cds/vizier.20730781 %R 1999HEAD....4.0901E %T Settling onto the Main Sequence: ROSAT Observations of H and chi Per %A Evans, Nancy Remage; Seward, Fredrick D. %F AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory) %J AAS/High Energy Astrophysics Division #4 %V 4 %D 04/1999 %P 09.01 %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/1999HEAD....4.0901E %B We have observed the double cluster h and chi Per with the ROSAT PSPC for 11 ksec. Emission is concentrated toward the two cluster centers, however the resolution at the distance of the clusters (2.4 kpc) is too poor to say whether the emission is diffuse or from a population of unresolved faint sources. 30 sources were found (at the 2.5 sigma level), with an X-ray luminosity of log L = 31.5 ergs sec(-1) or greater. These sources occur in the cluster nuclei, between the clusters and in the halo around the cluster pair. Individual optical sources cannot be identified, but because of the lack of correlation between the X-ray sources and B stars, we conclude that the X-rays are produced by late spectral type pre-main sequence stars. The X-ray sources are brighter than all but the brightest sources in the younger Orion Nebula cluster. These h and chi sources may represent the peak X-ray flux prior to the main sequence when stars have spun up more than the Orion Nobula stars but have still not fully contracted to the main sequence. %R 1999HEAD....4.2903S %T ROSAT Observations of the VELA Pulsar %A Seward, F. D.; Alpar, A.; Flanagan, C.; Markwardt, C.; McCulloch, P.; Ogelman, H. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Middle East Technical University, Turkey), AC(South African Radio Astronomy Observatory), AD(NASA Goddard Space Flight Center, Maryland), AE(University of Tasmania, Australia), AF(University of Wisconsin System) %J AAS/High Energy Astrophysics Division #4 %V 4 %D 04/1999 %P 29.03 %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/1999HEAD....4.2903S %B The ROSAT HRI has been used to monitor emission from the Vela Pulsar. Six observations span 2-1/2 years and 3 glitches. The summed data yield a good determination of the pulse shape and X-ray emission from the pulsar is found to be 11% pulsed with one broad and two narrow peaks. One observation occurred 15 days after a large glitch. No change in pulse structure was observed and any change in X-ray luminosity, if present, was less than 3%. Implications for neutron star structure are discussed. %R 1999ChNew...6...16S %T Peer Review %A Seward, Fred %J Chandra News %V 6 %D 02/1999 %P 16 %I PUB_HTML: Publisher Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1999ChNew...6...16S %R 1997ChNew...5...29S %T AXAF Users' Committee %A Seward, Fred %J Chandra News %V 5 %D 12/1997 %P 29 %I PUB_HTML: Publisher Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1997ChNew...5...29S %R 1997ApJ...485..221S %T Nonthermal X-Ray Emission from CTA 1 %A Slane, Patrick; Seward, Frederick D.; Bandiera, Rino; Torii, Ken'ichi; Tsunemi, Hiroshi %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Astronomical Observatory of Arcetri), AD(Osaka University, Department of Earth and Space Studies), AE(Japan Science and Technology Agency) %J The Astrophysical Journal %V 485 %D 08/1997 %P 221 %L 227 %K ISM: Individual: Alphanumeric: CTA 1, ISM: Supernova Remnants, X-Rays: ISM %C (c) 1997: The American Astronomical Society %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %I PUB_PDF: Publisher PDF; %I SIMBAD: SIMBAD Database at the CDS; %I HEASARC: NASA's High Energy Astrophysics Science Archive Research Center; %U https://ui.adsabs.harvard.edu/abs/1997ApJ...485..221S %B CTA 1 is a center-filled supernova remnant (SNR) whose morphology and spectrum indicate the presence of a central pulsar, a synchrotron nebula, and a thermal component associated with the expansion of the blast wave into the interstellar medium. The centrally bright emission surrounds the position of a faint point source of X-rays observed with the ROSAT PSPC. Here we report on ASCA observations that confirm the nonthermal nature of the diffuse emission from the central regions of the remnant. We also present evidence for weak thermal emission that appears to increase in strength toward the outer boundary of the SNR. Thus, CTA 1 appears to be an X-ray composite remnant. Both the aftermath of the explosive supernova event and the energetic compact core are observable. %H IOP %Y DOI: 10.1086/304416 %R 1997rxte.prop20259S %T Observation of Crab-Like Supernova Remnants %A Seward, Frederick %J RXTE Proposal %D 01/1997 %P 20259 %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/1997rxte.prop20259S %X RXTE Proposal #20259, Cycle 2 %B The supernova remnants 3C58 and G21.5-0.9 will be searched for pulsed emission. If a pulsar is found, the period derivative and inferred magnetic field will have extreme values if evolution has followed the standard model. If this is not the case, the standard model must be revised. We will also obtain very accurate measurement of the synchrotron emission spectrum of each remnant. %R 1997ICRC....5..173W %T VERITAS: The Very Energetic Radiation Imaging Telescope Array System. %A Weekes, T. C.; Akerlof, C.; Biller, S.; Breslin, A. C.; Catanese, M.; Carter-Lewis, D. A.; Cawley, M. F.; Dingus, B.; Fazio, G. G.; Fegan, D. J.; Finley, J.; Fishman, G.; Gaidos, J.; Gillanders, G. H.; Gorham, P.; Grindlay, J. E.; Hillas, A. M.; Huchra, J.; Kaaret, P.; Kertzman, M.; Kieda, D.; Krennrich, F.; Lamb, R. C.; Lang, M. J.; Marscher, A. P.; Matz, S.; McKay, T.; Muller, D.; Ong, R.; Purcell, W.; Rose, H. J.; Sembroski, G.; Seward, F. D.; Slane, P.; Swordy, S.; Tumer, T.; Ulmer, M.; Urban, M.; Wilkes, B. %J International Cosmic Ray Conference %V 5 %D 01/1997 %P 173 %K Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I Co-Reads: Co-Reads; %I EPRINT_HTML: arXiv Article; %I ADS_SCAN: Scanned Article (GIF); %I EPRINT_PDF: arXiv PDF; %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1997ICRC....5..173W %B A next generation atmospheric Cherenkov observatory is described based on the Whipple Observatory $\gamma$-ray telescope. A total of nine such imaging telescopes will be deployed in an array that will permit the maximum versatility and give high sensitivity in the 50 GeV - 50 TeV band (with maximum sensitivity from 100 GeV to 10 TeV). %Y DOI: 10.48550/arXiv.astro-ph/9706143 %Y eprintid: arXiv:astro-ph/9706143 %R 1996ApJ...471..887S %T ROSAT Observations of Two Southern Supernova Remnants %A Seward, F. D.; Kearns, K. E.; Rhode, K. L. %J The Astrophysical Journal %V 471 %D 11/1996 %P 887 %K ISM: SUPERNOVA REMNANTS, ISM: INDIVIDUAL ALPHANUMERIC: G327.1-1.1, ISM: INDIVIDUAL ALPHANUMERIC: G327.4+0.4, ISM: INDIVIDUAL NAME: KESTEVEN 27, X-RAYS: ISM %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I PUB_PDF: Publisher PDF; %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I HEASARC: NASA's High Energy Astrophysics Science Archive Research Center; %U https://ui.adsabs.harvard.edu/abs/1996ApJ...471..887S %B The supernova remnants G327.1-1.1 and G327.4+0.4 (Kes 27) are located 1°.5 apart in the constellation Norma. In 1980, Einstein IPC observations discovered that both were irregular filled-center X-ray sources with possible point sources superposed. This paper describes new ROSAT PSPC observations which both map the diffuse structure and clearly show several unresolved sources in each field. Both remnants have bright emitting regions inside the limb which might indicate the presence of high-energy electrons accelerated by a pulsar. The interior region is more prominent in G327.1-1.1 than in Kes 27.

The spectra are relatively strongly absorbed, as expected from distant remnants close to the Galactic plane. Comparison of the X-ray and radio maps of each remnant allows us to attribute some emission to a shell and some to the interior. With this information, a blast-wave model is used to derive approximate ages and energy release. Indications are that the Kes 27 supernova deposited ∼1O⁵¹ ergs in the surrounding medium. The G327.1-1.1 event probably deposited a factor of 3-1O less. %H IOP %Y DOI: 10.1086/178015 %R 1996ChNew...4...19S %T AXAF Users' Committee Report %A Seward, Fred %J Chandra News %V 4 %D 09/1996 %P 19 %I PUB_HTML: Publisher Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1996ChNew...4...19S %R 1996rftu.proc..277S %T Two southern SNR: G 327.1-1.1 and Kes 27. %A Seward, F. D.; Kearns, K. E.; Rhode, K. L. %J Roentgenstrahlung from the Universe %D 02/1996 %P 277 %L 278 %K Supernova Remnants: X-Ray Sources, Supernova Remnants: X-Ray Maps, Supernova Remnants: Radio Maps, Supernova Remnants: Structure %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I TOC: Table of Contents; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1996rftu.proc..277S %B The supernova remnants G 327.1-1.1 and G 327.4+0.4 (Kes 27) are located 1.5° apart in the galactic plane in the constellation Norma. Lamb and Markert (1981), using the Einstein IPC, discovered that both were irregular, filled-center X-ray sources with possible point sources superposed. ROSAT PSPC observations now map the diffuse structure and clearly show the unresolved sources in each field. As expected, the spectra are relatively strongly absorbed. Comparison of the X-ray and radio maps allows to attribute some emission to a shell and some to the interior. With this information, a blastwave model can be used to derive approximate age and energy release. Both remnants have bright emitting regions inside the limb which might indicate the presence of high energy electrons accelerated by a pulsar. This relatively bright interior region is more prominent in G 327.1-1.1 than in Kes 27. %R 1995exru.book.....S %T Exploring the X-Ray Universe %A Seward, Frederick D.; Charles, Philip A. %F AA(University of Oxford, UK), AB(Smithsonian Astrophysical Observatory) %J Exploring the X-Ray Universe %D 11/1995 %P 414 %K X-RAY ASTRONOMY %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I Co-Reads: Co-Reads; %I LIBRARY: Library Entry; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1995exru.book.....S %X LCCN: 92-34641 (BKS3); CALL NUMBER: QB472 .C46 1995 ISBN: 0521261821, 0521437121 %B Exploring the X-Ray Universe describes the view of the stars and galaxies that is obtained through X-ray telescopes. X-rays, which are invisible to human sight, are created in the cores of active galaxies, in cataclysmic stellar explosions, and in streams of gas expelled by the Sun and stars. The window on the heavens used by the X-ray astronomers shows the great drama of cosmic violence on the grandest scale.

This account of X-ray astronomy incorporates the latest findings from several observatories operating in space. These include the Einstein Observatory operated by NASA, and the EXOSAT satellite of the European Space Agency. The book covers the entire field, with chapters on stars, supernova remnants, normal and active galaxies, clusters of galaxies, the diffuse X-ray background, and much more. The authors review basic principles, include the necessary historical background, and explain exactly what we know from X-ray observations of the Universe. %R 1995ApJ...453..284S %T X-Ray Emission from the Supernova Remnant CTA 1 %A Seward, F. D.; Schmidt, B.; Slane, P. %J The Astrophysical Journal %V 453 %D 11/1995 %P 284 %K GALAXIES: SEYFERT, ISM: INDIVIDUAL ALPHANUMERIC: CTA 1, ISM: SUPERNOVA REMNANTS, X-RAYS: ISM %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %I HEASARC: NASA's High Energy Astrophysics Science Archive Research Center; %U https://ui.adsabs.harvard.edu/abs/1995ApJ...453..284S %B Three pointings of the ROSAT PSPC have been used to map the X-ray emission of CTA 1. Emission is brightest at the center and extends in all directions to the boundaries of the remnant. The luminosity is model-dependent and (at 1.4 kpc), is, L_X(0.1 24 keV) = 5-8 x 10³⁴ ergs s^-1. Emission from the center is harder and considerably brighter than that from the rim. Spectra from several parts of the remnant are fitted with two component models. Both a two-temperature thermal model and a model consisting of a power law and a soft thermal component produce good fits to all regions. The spectra do not allow us to distinguish between a remnant with hot evaporated material at the center, or an old Crab-like remnant. Both are plausible models for CTA 1.

The ROSAT HRI was used to obtain an accurate location of a bright unresolved source within the remnant. This is identified as a background active galactic nucleus. Properties of eight weaker, unresolved X-ray sources within or nearby the remnant are tabulated. %H IOP %Y DOI: 10.1086/176388 %R 1995ChNew...3...11S %T AXAF Users' Committee Report %A Seward, Fred %J Chandra News %V 3 %D 09/1995 %P 11 %I PUB_HTML: Publisher Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1995ChNew...3...11S %R 1995ApJ...449..681S %T A ROSAT-detected, New Galactic Supernova Remnant in Sagittarius, G13.3-1.3 %A Seward, F. D.; Dame, T. M.; Fesen, R. A.; Aschenbach, B. %J The Astrophysical Journal %V 449 %D 08/1995 %P 681 %K ISM: SUPERNOVA REMNANTS, ISM: INDIVIDUAL ALPHANUMERIC: G13.3-1.3, X-RAYS: ISM %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I HEASARC: NASA's High Energy Astrophysics Science Archive Research Center; %U https://ui.adsabs.harvard.edu/abs/1995ApJ...449..681S %X LBN 52 not standard format %B Faint and diffuse soft X-ray emission, coincident with [S II] strong optical filaments, probably marks a previously unrecognized supernova remnant (SNR) in Sagittarius (1 = 13.3, b = -1.3). ROSAT PSPC data show soft X-rays from an area 40' × 70' with a flux of 1.3 × 10^-11 erg cm^-2 s^-1 between 0.1-2.4 keV. Optical interference-filter images taken of the region reveal a 20' long complex of relatively bright filaments located along the south central boundary of the X-ray region which may be associated with a ridge of faint 11 cm continuum emission. Optical spectra of these filaments show strong [S II] λλ6716, 6731 emission ([S II]/ Hα = 0.85) and [O I] λλ6300, 6364 characteristic of shocked interstellar gas found in SNRs. Both X-rays and optical emissions along the source's NE extent show strong absorption by the dust regions Lynds 332, 336, and 342, indicating a location behind these nebulae. CO emission from this region has been mapped and a kinematic distance derived for absorbing material. The remnant is shown to lie between two absorbing regions located at distances of 2 and 4 kpc. %H IOP %Y DOI: 10.1086/176089 %R 1995ApJ...447..211K %T ROSAT Observations of the Supernova Remnant W51C %A Koo, Bon-Chul; Kim, Kee-Tae; Seward, Frederick D. %J The Astrophysical Journal %V 447 %D 07/1995 %P 211 %K ISM: INDIVIDUAL ALPHANUMERIC: W51, ISM: SUPERNOVA REMNANTS, RADIO CONTINUUM: ISM, X-RAYS: ISM %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I HEASARC: NASA's High Energy Astrophysics Science Archive Research Center; %U https://ui.adsabs.harvard.edu/abs/1995ApJ...447..211K %B We have carried out ROSAT X-ray observations of the W51C supernova remnant (SNR). The SNR appears as an elongated (50' × 38') structure along the east-west direction. In contrast to its shell-type morphology in radio continuum, the SNR has both center-filled and shell-type morphologies in X-ray structure. The boundary of the radio structure matches well with that of the X-ray in the southeast. To the west, the X-ray structure appears to extend beyond the radio continuum shell. High-resolution (40") interferometric 21 cm continuum observation shows a thin shell located within the X-ray structure. The thin shell appears to surround the central X-ray-bright region.

The X-ray spectrum of the SNR becomes systematically harder toward the west. By comparing the spectral hardness with the distribution of molecular gas in this region, we have found that the spectral hardening is due to the selective absorption by intervening interstellar gas. The W51C SNR is considered to be behind the "high-velocity molecular stream" at a mean distance of 5.6 kpc. The average X-ray spectrum of the SNR can be fitted well by the Raymond-Smith thermal model with T_e = 3.4 × 10⁶ K. We apply the Sedov and evaporative (White & Long 1991) models to derive the SNR parameters. Both models yield an age of ∼3 × 10⁴ yr and an explosion energy of 3.6 × 10⁵¹ ergs, which is larger than the canonical value of a single supernova explosion. We discuss the implications of the large energy requirement and the complex X-ray and radio morphologies. %H IOP %Y DOI: 10.1086/175867 %R 1995ApJ...439..715S %T A ROSAT Observation of the Supernova Remnant Kesteven 79 %A Seward, F. D.; Velusamy, T. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics) %J The Astrophysical Journal %V 439 %D 02/1995 %P 715 %K Interstellar Matter, Radio Observation, Stellar Envelopes, Supernova Remnants, X Ray Astronomy, X Ray Spectra, Astronomical Models, Brightness, Emission Spectra, Luminosity, Rosat Mission, Shock Wave Luminescence, Spectrum Analysis, Astrophysics, ISM: SUPERNOVA REMNANTS, ISM: INDIVIDUAL NAME: KESTEVEN 79, X-RAYS: ISM %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I HEASARC: NASA's High Energy Astrophysics Science Archive Research Center; %U https://ui.adsabs.harvard.edu/abs/1995ApJ...439..715S %B Kes 79 was observed with the ROSAT Position Sensitive Proportional Counter (PSPC) and High Resolution Imager (HRI). Some X-ray emission comes from a faint outer region, well correlated with the outer shell. Most emission is from a bright diffuse inner region where there are also bright radio filaments. The X-ray spectrum is fitted with a thermal model with temperature 1.3 keV. Variations in spectra from different regions are small. There is no X-ray evidence for an internal neutron star. Remnant characteristics are derived using a simple blast-wave model. The observed X-ray absorption is less than expected. It is possible that the remnant is closer than the published distance of 10 kpc. %H IOP %Y DOI: 10.1086/175211 %R 1994MNRAS.271L...1R %T X-ray evidence for the association of G11.2-0.3 with the supernova of 386 AD. %A Reynolds, S. P.; Lyutikov, M.; Blandford, R. D.; Seward, F. D. %J Monthly Notices of the Royal Astronomical Society %V 271 %D 11/1994 %P L1 %L L4 %K Supernova Remnants: X-Ray Maps, Supernova Remnants: Shock Waves, Supernova Remnants: Distances %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I HEASARC: NASA's High Energy Astrophysics Science Archive Research Center; %U https://ui.adsabs.harvard.edu/abs/1994MNRAS.271L...1R %B We present ROSAT observations of the radio-bright supernova remnant G1 1.2-0.3 which support the hypothesis that it is the remnant of the historical supernova SN 386 AD. The PSPC data imply a post-shock temperature of kT= 2.4 (+2.3, -1.0) keV (95 per cent confidence limits), equivalent to a shock speed of 1400 km s - , and an absorbing column density NH = 1.3 (+0.4, -0.2)x 1022 , for a homogeneous, equilibrium plasma model. For an assumed age of 1607 yr, these data imply a distance of 9 kpc and a peak apparent magnitude of about 2 mag, consistent with a Type Ia supernova. Key words: supernovae: individual: SN 386 AD - supernova remnants - X-rays: ISM. %H OUP %Y DOI: 10.1093/mnras/271.1.L1 %R 1994ChNew...2...13S %T AXAF Users' Committee Report %A Seward, Fred %J Chandra News %V 2 %D 08/1994 %P 13 %I PUB_HTML: Publisher Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1994ChNew...2...13S %R 1994JGR....9914799W %T ROSAT observations of the jupiter aurora %A Waite, J. H., Jr.; Bagenal, F.; Seward, F.; Na, C.; Gladstone, G. R.; Cravens, T. E.; Hurley, K. C.; Clarke, J. T.; Elsner, R.; Stern, S. A. %F AA(Southwest Research Institute, Texas), AB(Southwest Research Institute, Texas), AC(Harvard College Observatory), AD(Harvard College Observatory), AE(Southwest Research Institute, Texas), AF(Southwest Research Institute, Texas), AG(University of California, Berkeley), AH(University of California, Berkeley), AI(NASA Goddard Space Flight Center, Maryland), AJ(NASA Goddard Space Flight Center, Maryland) %J Journal of Geophysical Research %V 99 %D 08/1994 %P 14799 %L 14810 %K Auroras, Bremsstrahlung, Jupiter (Planet), Proportional Counters, Ions, Iue, Line Spectra, Particle Precipitation, Rosat Mission, X Ray Spectra, Magnetospheric Physics: Auroral phenomena, Atmospheric Composition and Structure: Airglow and aurora, Magnetospheric Physics: Energetic particles, precipitating, Magnetospheric Physics: Planetary magnetospheres %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %I MAST: Mikulski Archive for Space Telescopes; %I HEASARC: NASA's High Energy Astrophysics Science Archive Research Center; %U https://ui.adsabs.harvard.edu/abs/1994JGR....9914799W %B Röntgen satellite (ROSAT) high-resolution imager (HRI) and position sensitive proportional counter (PSPC) observations of Jupiter obtained in April 1991 and May 1992 reveal soft X ray emissions apparently associated with Jupiter's aurora and similar to X ray emissions observed earlier by the Einstein Observatory. The HRI images show emission mainly from Jupiter's northern hemisphere at all Jovian longitudes observed, and there is some indication of a longitudinal modulation of the emission in phase with the well-known ultraviolet modulation of the northern aurora. The PSPC data reveal a very soft spectrum. Comparison of the observed spectrum with models for both electron bremsstrahlung radiation and line emission for S and O ions indicates that the line spectrum gives a much better statistical fit to the observed spectrum. The X ray observations presented here therefore support the hypothesis that ion precipitation is the most likely cause of the Jovian X ray emissions, a result first suggested by the Einstein results [Metzger et al., 1983]. %Y DOI: 10.1029/94JA01005 %R 1994ApJ...421..581S %T The Outer Shell of SNR 0540-69.3 %A Seward, F. D.; Harnden, F. R., Jr. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics) %J The Astrophysical Journal %V 421 %D 02/1994 %P 581 %K Astronomical Models, Magellanic Clouds, Shock Waves, Spaceborne Astronomy, Supernova Remnants, X Ray Astronomy, Luminosity, Rosat Mission, Astronomy, GALAXIES: MAGELLANIC CLOUDS, ISM: INDIVIDUAL ALPHANUMERIC: 0540-69.3, ISM: SUPERNOVA REMNANTS, X-RAYS: ISM %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %I MAST: Mikulski Archive for Space Telescopes; %I HEASARC: NASA's High Energy Astrophysics Science Archive Research Center; %U https://ui.adsabs.harvard.edu/abs/1994ApJ...421..581S %B The supernova remnant 0540-69.3 in the Large Magellanic Cloud has been observed with the ROSAT HRI detector. The outer shell was resolved from the bright central region and its X-ray morphology and luminosity determined. One-quarter of the soft X-rays originate in this shell. This result and a simple blastwave model imply that the energy release in the supernova was about 2 x 10^51^ ergs. %H IOP %Y DOI: 10.1086/173673 %R 1994sao..rept.....E %T Investigation relative to the Roentgen Satellite (ROSAT) %A Elvis, Martin S.; Primini, Francis A.; Fabbiano, Guiseppina; Harris, Daniel E.; Jones-Forman, Christine; Trinchieri, Ginevra; Golub, Leon; Bookbinder, Jay; Seward, Frederick D.; Zombeck, Martin V. %F AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory), AC(Smithsonian Astrophysical Observatory), AD(Smithsonian Astrophysical Observatory), AE(Smithsonian Astrophysical Observatory), AF(Smithsonian Astrophysical Observatory), AG(Smithsonian Astrophysical Observatory), AH(Smithsonian Astrophysical Observatory), AI(Smithsonian Astrophysical Observatory), AJ(Smithsonian Astrophysical Observatory) %J Smithsonian Astrophysical Observatory Report %D 01/1994 %K Radio Astronomy, Rosat Mission, Spaceborne Astronomy, Supernova Remnants, X Ray Astronomy, X Ray Sources, Andromeda Galaxy, Astrophysics, Cataclysmic Variables, Cygnus Constellation, Gravitational Lenses, Magellanic Clouds, Quasars, Astronomy %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/1994sao..rept.....E %B Reports include: High Resolution Observations of the Central Region of M31; The X-ray Emission of Low-X-ray-Luminosity Early-Type Galaxies: Gas Versus Compact Sources; Interaction Between Cluster Gas and Radio Features of Cygnus A; Hot Gas and Dark Halos in Early-Type Galaxies; A Gravitational Lens in X-rays - 0957+461; How Massive are Early-Type Galaxies?; Three Crab-Like SNR in the Large Magellanic Cloud; and Soft X-ray Emission from Boundary Layers in Cataclysmic Variables. Papers submitted to the Astrophysical Journal are attached. %R 1993AAS...183.8303R %T X-ray Observations of Two Radio-Bright Supernova Remnants %A Reynolds, S. P.; Seward, F. D.; Blandford, R. D. %F AA(North Carolina State University), AB(Harvard Smithsonian Center for Astrophysics), AC(California Institute of Technology) %J American Astronomical Society Meeting Abstracts %V 183 %D 12/1993 %P 83.03 %I ABSTRACT: Abstract; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I HEASARC: NASA's High Energy Astrophysics Science Archive Research Center; %U https://ui.adsabs.harvard.edu/abs/1993AAS...183.8303R %B X-ray emission from young supernova remnants results from two processes: the bulk heating of ions, primarily, at the blast wave, and the subsequent heating of electrons due either to Coulomb collisions with hot ions or to (faster) collective processes such as plasma instabilities. The detailed X-ray image of a SNR can shed light on the processes by which electrons are heated, but also can simply locate the shock wave, or at least provide a lower limit to the shock radius. Radio-bright remnants must be producing new energetic electrons and/or magnetic field behind the shock wave, but the mechanisms are unclear. We exhibit ROSAT PSPC and HRI images of two of the ten highest radio-surface-brightness SNRs in the Galaxy, G11.2--0.3 and 3C 397, and compare them to radio images. The correspondence is excellent. Images in both wavelength regions have unresolved edges at about 1' resolution suggesting that the enhanced synchrotron emissivity is produced immediately at the shock front. Azimuthal brightness variations in the shells are correlated in the two wavelength regions, suggesting that both thermal-electron heating and relativistic-electron acceleration occur through processes sensitive to the same properties of the external medium, such as the obliquity angle between the local shock normal and the upstream magnetic field. We also discuss other features of the X-ray observations. %R 1993AAS...183.8302S %T ROSAT Observations of the Supernova Remnant Kes 79 %A Seward, F. D.; Velusamy, T. %J American Astronomical Society Meeting Abstracts %V 183 %D 12/1993 %P 83.02 %I CITATIONS: Citations to the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1993AAS...183.8302S %R 1993Sci...262..444S %T Neutron Stars. (Book Reviews: Isolated Pulsars.) %A Seward, Fred %J Science %V 262 %D 10/1993 %P 444 %L 445 %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1993Sci...262..444S %Y DOI: 10.1126/science.262.5132.444 %R 1993Sci...262..444V %T Neutron Stars. (Book Reviews: Isolated Pulsars.) %A Seward, Fred %J Science %V 262 %D 10/1993 %P 444 %L 445 %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1993Sci...262..444V %Y DOI: 10.1126/science.262.5132.444 %R 1993ChNew...1....4S %T The AXAF Users' Committee %A Seward, Fred %J Chandra News %V 1 %D 09/1993 %P 4 %I PUB_HTML: Publisher Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1993ChNew...1....4S %R 1993AIPC..280..808R %T An X-ray counterpart to the 5 March 1979 gamma ray burst? %A Rothschild, R. E.; Lingenfelter, R. E.; Seward, F. D.; Vancura, O. %J Compton Gamma-ray Observatory %V 280 %D 01/1993 %P 808 %L 812 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I TOC: Table of Contents; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1993AIPC..280..808R %B We have searched the Einstein HRI images of the supernova remnant N49 for evidence of any point-like x-ray enhancement within the error box of the repeating gamma ray burst source GBS 0525-66, the source of the 5 March 1979 and other bursts. Although nothing stands out strongly from the diffuse supernova emission, a most likely location exists, centered within an unusual, bright, x-ray emitting region. Emission is brightest at location 5^h 25^m 56.^s5 and -66° 07' 05` (1950). We suggest that a 5` radius circle, centered here, provides a more precise error box for study at other wavelengths. The x-ray flux from a possible point-like source at this position is 1.0±0.3×10^-12 ergs cm^-2 s^-1 in the range 0.5-4.5 keV. We discuss models for the emission, and conclude that thermonuclear runaway on a nearby (<1 kpc) neutron star or a starquake on a neutron star at the distance of the LMC (55 kpc) is consistent with the data. %H AIP %Y DOI: 10.1063/1.44225 %R 1993ASPC...52..484M %T Verification of the PROS Timing Analysis Package %A Manning, K. R.; Conroy, M. A.; Deponte, J.; Moran, J. F.; Primini, F. A.; Seward, F. D.; Aschenbach, B. %F AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory), AC(Smithsonian Astrophysical Observatory), AD(Smithsonian Astrophysical Observatory), AE(Smithsonian Astrophysical Observatory), AF(Smithsonian Astrophysical Observatory), AG(Max-Planck- Institute for Extraterrestrial Physics, Garching) %J Astronomical Data Analysis Software and Systems II %V 52 %D 01/1993 %P 484 %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I TOC: Table of Contents; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1993ASPC...52..484M %R 1992ChA&A..16..278W %T SNRs MSH 15-56 and CTA %A Wang, Zhen-Ru; Qu, Qin-Yue; Seward, Fred %F AA(Nanjing University, China), AB(Nanjing University, China), AC(Harvard Smithsonian Center for Astrophysics) %J Chinese Astronomy and Astrophysics %V 16 %D 09/1992 %P 278 %L 283 %K H Alpha Line, Satellite Observation, Spaceborne Astronomy, Supernova Remnants, X Ray Astronomy, Emission Spectra, Extragalactic Radio Sources, Heao 2, Astrophysics, Supernovae-supernova remnants-X-ray observations %C (c) 1992 Elsevier Science B.V. All rights reserved. %I ABSTRACT: Abstract; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1992ChA&A..16..278W %B This paper gives the observed data of MSH 15-56 and CTA 1 from the Einstein satellite in detail. According to these data, some physical parameters or characteristics of MSH 15-56 and CTA 1 are derived and discussed. The model derived radio flux of them is comparable with that observed before. %Y DOI: 10.1016/0275-1062(92)90067-L %R 1992AAS...181.6005Y %T The Detection of Pulsed X-Ray Emission from a Nearby Radio Pulsar %A Yancopoulos, S.; Helfand, D. J.; Hamilton, T. T.; Halpern, J. P.; Seward, F. D.; Becker, R. H. %J American Astronomical Society Meeting Abstracts %V 181 %D 09/1992 %P 60.05 %I CITATIONS: Citations to the Article; %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1992AAS...181.6005Y %R 1992fxra.conf..395W %T SNRs MSH 15-56 and CTA 1 %A Wang, Z. -R.; Qu, Q. -Y.; Seward, F. %J Frontiers Science Series %D 01/1992 %P 395 %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/1992fxra.conf..395W %R 1992AcApS..12..101W %T SNRs MSH 15-56 and CTA 1. %A Wang, Z.; Qu, Q.; Seward, F. %J Acta Astrophysica Sinica %V 12 %D 01/1992 %P 101 %L 106 %I CITATIONS: Citations to the Article; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1992AcApS..12..101W %R 1991AJ....102.2047S %T A Large Radio Galaxy Behind the Supernova Remnant HB9 %A Seward, F. D.; Fabricant, D. G.; Kirshner, R. P.; McClintock, J. E.; Smith, R. C.; Remillard, R. A. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics), AE(Harvard Smithsonian Center for Astrophysics), AF(Massachusetts Institute of Technology) %J The Astronomical Journal %V 102 %D 12/1991 %P 2047 %K Radio Galaxies, Supernova Remnants, Extragalactic Radio Sources, Galactic Clusters, X Ray Sources, Astrophysics, RADIO SOURCES: GALAXIES, NEBULAE: SUPERNOVA REMNANTS %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %U https://ui.adsabs.harvard.edu/abs/1991AJ....102.2047S %B HB9 is a 2^deg^ diameter radio shell with x-ray emission from a broad diffuse band in the interior. Within this band, a weak unresolved x-ray source coincides with the radio source 4C 46.09. To identify this source we have obtained CCD I and V band pictures and a spectrum. The source is a galaxy at redshift 0.195, and is therefore only accidentally aligned with HB9. The galaxy is large and bright and has the characteristics of a cD galaxy, often found at the center of clusters. If the galaxy is centered in a cluster, some of the surrounding diffuse x-rays may also be extragalactic. %H IOP %Y DOI: 10.1086/116027 %R 1991BAAS...23.1452S %T FeLiX: An X-Ray Telescope to Perform a Medium Angular Resolution All-Sky Survey in the 2-10 keV Band %A Slane, P.; Elvis, M.; Fabbiano, G.; Hughes, J.; Seward, F.; Szentgyorgyi, A.; Worrall, D. %J Bulletin of the American Astronomical Society %V 23 %D 09/1991 %P 1452 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1991BAAS...23.1452S %R 1991ApJS...76.1127V %T The Einstein Objective Grating Spectrometer Survey of Galactic Binary X-Ray Sources %A Vrtilek, S. D.; McClintock, J. E.; Seward, F. D.; Kahn, S. M.; Wargelin, B. J. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(University of California, Berkeley), AE(University of California, Berkeley) %J The Astrophysical Journal Supplement Series %V 76 %D 08/1991 %P 1127 %K Gratings (Spectra), Heao 2, Proportional Counters, X Ray Binaries, X Ray Spectroscopy, High Resolution, Spectral Resolution, X Ray Spectra, Astrophysics, X-RAYS: BINARIES, X-RAYS: SPECTRA %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1991ApJS...76.1127V %B The results of observations of 22 bright Galactic X-ray point sources are presented, and the most reliable measurements to date of X-ray column densities to these sources are derived. The results are consistent with the idea that some of the objects have a component of column density intrinsic to the source in addition to an interstellar component. The K-edge absorption due to oxygen is clearly detected in 10 of the sources and the Fe L and Ne K edges are detected in a few. The spectra probably reflect emission originating in a collisionally excited region combined with emission from a photoionized region excited directly by the central source. %H IOP %Y DOI: 10.1086/191594 %R 1991AJ....102..676V %T G33.6+0.1: A Shell Type Supernova Remnant With Unusual Structure %A Velusamy, T.; Becker, R. H.; Seward, F. D. %F AA(Tata Institute of Fundamental Research, India), AB(University of California, Davis; Lawrence Livermore National Laboratory, California), AC(Smithsonian Astrophysical Observatory) %J The Astronomical Journal %V 102 %D 08/1991 %P 676 %K Radio Sources (Astronomy), Supernova Remnants, Very Large Array (Vla), X Ray Imagery, Emission Spectra, H Ii Regions, Radio Astronomy, Radio Emission, Astrophysics, NEBULAE: SUPERNOVA REMNANTS %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1991AJ....102..676V %B The morphology of Supernova Remnant G33.6 + 0.1 (Kes 79) has been studied in the X-rays with Einstein and in the radio wavelengths using the VLA. Multifrequency high resolution observations of the VLA at 327, 1500, and 5000 MHz are used to study the radio spectrum and polarization. The radio emission shows well formed outer shell structure and very bright central emission. Although the overall distribution of spectral index (about -0.6 to -0.75) is consistent with that of shell type remnants, the bright filamentary emission along the 'inner ring' has relatively flatter spectrum (alpha about -0.4). Both radio and X-rays show strong central emission; existence of a plerion near the center cannot be ruled out. The X-ray image does not show the characteristic limb brightening for shell type SNRs. The X-ray and radio morphology may be understood in terms of very thick shell and the bright central emission as due to reverse shock. %H IOP %Y DOI: 10.1086/115901 %R 1991BAAS...23..918S %T A Large Radio Galaxy Behind the Supernova Remnant HB 9 %A Seward, F. D.; Fabricant, D. G.; Kirshner, R. P.; McClintock, J. E.; Remillard, R. A.; Smith, R. C. %J Bulletin of the American Astronomical Society %V 23 %D 03/1991 %P 918 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1991BAAS...23..918S %R 1990ApJS...73..781S %T Einstein Observations of Galactic Supernova Remnants %A Seward, Frederick D. %F AA(Harvard Smithsonian Center for Astrophysics) %J The Astrophysical Journal Supplement Series %V 73 %D 08/1990 %P 781 %K Heao 2, Milky Way Galaxy, Supernova Remnants, X Ray Sources, Brightness Distribution, Classifying, Image Processing, Proportional Counters, Astrophysics, NEBULAE: SUPERNOVA REMNANTS, X-RAYS: SOURCES %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I TOC: Table of Contents; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I CDS: Strasbourg Astronomical Data Center; %U https://ui.adsabs.harvard.edu/abs/1990ApJS...73..781S %B This paper summarizes the observations of Galactic supernova remnants with the imaging detectors of the Einstein Observatory. X-ray surface brightness contours of 47 remnants are shown together with gray-scale pictures. Count rates for these remnants have been derived and are listed for the HRI, IPC, and MPC detectors. %H IOP %Y DOI: 10.1086/191489 %R 1990ApJ...351..157T %T A Further Study of the Molecular Cloud Associated with the Supernova Remnant G109.1-1.0 %A Tatematsu, Ken'ichi; Fukui, Yasuo; Iwata, Takahiro; Seward, Frederick D.; Nakano, Makoto %F AA(Nagoya University, Japan), AB(Nagoya University, Japan), AC(Nagoya University, Japan), AD(Harvard Smithsonian Center for Astrophysics), AE(Oita University, Japan) %J The Astrophysical Journal %V 351 %D 03/1990 %P 157 %K Astronomical Spectroscopy, Molecular Clouds, Supernova Remnants, X Ray Sources, Absorption Spectra, Carbon Monoxide, Electron Transitions, Heao 2, Particle Acceleration, X Ray Spectra, Astrophysics, INTERSTELLAR: MOLECULES, NEBULAE: INDIVIDUAL ALPHANUMERIC: G109.1-1.0, NEBULAE: INDIVIDUAL ALPHANUMERIC: CTB 109, NEBULAE: SUPERNOVA REMNANTS, X-RAYS: SOURCES, X-RAYS: SPECTRA %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1990ApJ...351..157T %B The region of the semicircular SNR G109.1-1.0 is studied on the basis of CO observations with a 45-m radio telescope and X-ray data from the archive of the Einstein Observatory. By observing the J = 1-0 transition of CO at 115 GHz, the distribution of the molecular cloud associated with the remnant is investigated in detail. The resolution of the CO mapping observations is 0.6-1.2 pc and the number of the CO spectra obtained is about 2000. The molecular ridge (CO arm), which was known to show an apparent anticorrelation with the curled x-ray jetlike feature of the remnant, is resolved into two CO filaments. The hardness of the X-ray spectrum toward the CO arm is consistent with the column densities of the two CO filaments. However, the overall appearance of the remnant will not be affected very much by the absorption, because the X-ray absorption is found to be a minor effect. %H IOP %Y DOI: 10.1086/168452 %R 1990ixra.conf..319S %T Einstein Observations of Supernova Remnants %A Seward, F. D. %J Imaging X-Ray Astronomy. A Decade of Einstein Observatory Achievements %D 01/1990 %P 319 %I ABSTRACT: Abstract; %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/1990ixra.conf..319S %B Einstein was pointed at ≡80 galactic supernova remnants. 60% of these were detected and data from the imaging instruments has been gathered into a catalog. %R 1990ixra.conf..241S %T A New Boundary for the VELA Supernova Remnant %A Seward, F. D. %J Imaging X-Ray Astronomy. A Decade of Einstein Observatory Achievements %D 01/1990 %P 241 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/1990ixra.conf..241S %B The Vela supernova remnant, at a distance of 0.5 kpc, is one of the closest SNR to Earth. It was first detected as a conglomerate of radio sources, Vela X, Y, and Z. The remnant was surveyed with the Einstein IPC in 1979 - 80. 33 fields covered the Vel XYZ radio source. The resultant merged X-ray image shows the rim of the remnant in the north and east, fades below threshold in the west, and in the south, the boundary extends beyond the observed region. %R 1989BAAS...21R1203L %T Distances to Galactic Supernova Remnants %A Li, H.; Seward, F. D. %J Bulletin of the American Astronomical Society %V 21 %D 09/1989 %P 1203 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1989BAAS...21R1203L %R 1989SSRv...49..385S %T The Crab-Like Supernova Remnants %A Seward, Frederick D. %F AA(Harvard Smithsonian Center for Astrophysics) %J Space Science Reviews %V 49 %D 04/1989 %P 385 %L 423 %K Crab Nebula, Neutron Stars, Supernova Remnants, Synchrotron Radiation, Heao 2, X Ray Astronomy, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %U https://ui.adsabs.harvard.edu/abs/1989SSRv...49..385S %B About twenty galactic supernova remnants contain, or are suspected to contain, internal neutron stars. These are observed as pulsing sources or through radiation from surrounding synchrotron nebulae. The Crab Nebula is the most famous example. Similar, but less luminous, nebulae have been identified through radio and X-ray morphology and spectra. This review emphasizes the X-ray observations and is based on images obtained with the Einstein Observatory. These images are illustrated for most remnants and some have not been published previously. There is a great variety of observed characteristics. A typical SNR in this class appears as a patchy shell of hot gas with a contribution from an energetic pulsar at the center. Both the luminosity of the shell and the luminosity powered by the pulsar can vary over a wide range. Remnants reviewed range from the Crab, in which the pulsar-powered component is overwhelming, to RCW 103, in which a central object is marginally observed through a bright shell. %Y DOI: 10.1007/BF00241871 %R 1989AJ.....97..481S %T X Rays from G54.1+0.3 %A Seward, F. D. %F AA(Harvard Smithsonian Center for Astrophysics) %J The Astronomical Journal %V 97 %D 02/1989 %P 481 %K Cosmic X Rays, Radio Sources (Astronomy), Supernova Remnants, Absorption Spectra, Abundance, Brightness Distribution, Power Spectra, Astrophysics, NEBULAE: SUPERNOVA REMNANTS, NEBULAE: INDIVIDUAL %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1989AJ.....97..481S %B X rays have been observed from the Crab-like SNR G54.1 + 0.3. Interstellar absorption is high, implying a large distance to the source. %H IOP %Y DOI: 10.1086/114997 %R 1988ApJ...335..215P %T A Comprehensive Study of the X-Ray Structure and Spectrum of IC 443 %A Petre, R.; Szymkowiak, A. E.; Seward, F. D.; Willingale, R. %F AA(NASA Goddard Space Flight Center, Maryland), AB(NASA Goddard Space Flight Center, Maryland), AC(Harvard Smithsonian Center for Astrophysics), AD(University of Leicester, UK) %J The Astrophysical Journal %V 335 %D 12/1988 %P 215 %K Astronomical Spectroscopy, Supernova Remnants, X Ray Sources, H Ii Regions, Molecular Clouds, Spectrophotometry, Stellar Envelopes, Astrophysics, NEBULAE: INDIVIDUAL ALPHANUMERIC: IC 443, NEBULAE: SUPERNOVA REMNANTS, X-RAYS: SOURCES %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1988ApJ...335..215P %B This paper presents the results of a comprehensive study of the X-ray emission from the supernova remnant IC 443, using the solid state spectrometer, IPC, and high-resolution images of the Einstein Observatory, and the medium-energy detector of the HEAO 1 A-2 experiment. A soft X-ray appearance was observed, highly atypical of a supernova remnant in the adiabatic phase, with little correlation between X-ray and optical or radio features. The best-fit models of the low-energy X-ray spectrum of the brightest area of the remnant suggest either that the remnant has not yet attained ionization equilibrium or that the X-rays arise in a multiphase medium. Pronounced soft X-ray spectral differences across the remnant are accounted for by variations in absorption by an intervening molecular cloud. The analysis suggests that, despite the atypical X-ray appearance, the X-ray emission in IC 443 is probably confined to a thin (0.1 pc) shell. %H IOP %Y DOI: 10.1086/166922 %R 1988feta.conf....6S %T The Einstein Supernova Remnant Catalog %A Seward, F. D. %J From Einstein to AXAF, A Symposium to Celebrate the 10th Anniversary of the launch of HEAO-2, the Einstein Observatory %D 11/1988 %P 6 %U https://ui.adsabs.harvard.edu/abs/1988feta.conf....6S %R 1988feta.conf...24S %T The Vela Supernova Remnant %A Seward, Frederick D. %J From Einstein to AXAF, A Symposium to Celebrate the 10th Anniversary of the launch of HEAO-2, the Einstein Observatory %D 11/1988 %P 24 %U https://ui.adsabs.harvard.edu/abs/1988feta.conf...24S %R 1988ApJ...332..199S %T Pulsars, X-Ray Synchrotron Nebulae, and Guest Stars %A Seward, Frederick D.; Wang, Zhen-Ru %F AA(Harvard Smithsonian Center for Astrophysics), AB(Nanjing University, China) %J The Astrophysical Journal %V 332 %D 09/1988 %P 199 %K Neutron Stars, Pulsars, Stellar Coronas, Stellar Rotation, Supernova Remnants, X Ray Astronomy, Charged Particles, Energy Dissipation, Magnetic Dipoles, Radio Sources (Astronomy), Relativistic Particles, Astrophysics, NEBULAE: SUPERNOVA REMNANTS, PULSARS, RADIATION MECHANISMS, STARS: NEUTRON, STARS: ROTATION %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %U https://ui.adsabs.harvard.edu/abs/1988ApJ...332..199S %B X-ray observations of supernova remnants and radio pulsars are used to derive luminosities of neutron stars and synchrotron nebulae. Observations of known isolated pulsars are used to develop an empirical relationship between the X-ray luminosity and the rate of loss of rotational energy. This is used to derive the characteristics of pulsars hidden in remnants which show evidence for a central compact object or associated nebular emission, but no clear pulsed signal from the neutron star itself. We discuss possible periods and period derivatives for the hidden pulsars. Some might have periods as long as 0.5 s and period derivatives considerably higher than that of PSR 1509-58, currently the pulsar with the highest known period derivative. %H IOP %Y DOI: 10.1086/166646 %R 1988BAAS...20.1049S %T The Vela Supernova Remnant %A Seward, F. D. %J Bulletin of the American Astronomical Society %V 20 %D 09/1988 %P 1049 %I CITATIONS: Citations to the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1988BAAS...20.1049S %R 1988AcASn..29...33W %T Earth Rocks on Mars: Must Planetary Quarantine Be Rethought? %A Wang, Zhen-Ru; Seward, F. D. %F AA(Nanjing University, China; China Center of Advanced Science and Technology), AB(Harvard Smithsonian Center for Astrophysics) %J Acta Astronomica Sinica %V 29 %D 09/1988 %P 33 %K Crab Nebula, Pulsars, Supernova Remnants, X Ray Sources, Photons, Stellar Luminosity, Surface Properties, Astronomy %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %U https://ui.adsabs.harvard.edu/abs/1988AcASn..29...33W %B The total X-ray luminosity of both isolated pulsar and its surrounding nebula is detected for ten Crab-like supernova remnants from Einstein observation by use of the same instrument calibrations. A statistical relation between the total X-ray luminosities and the rotating energy loss rate of the pulsars is obtained. Finally, the authors have a preliminary discussion on some Crab-like supernova remnants with compact sources but no pulsating signals being observed. %R 1988ChA&A..12..212W %T An X-ray investigation of crab-like supernova remnants %A Wang, Zhen-ru; Seward, F. D. %F AA(China Center of Advanced Science and Technology), AB(China Center of Advanced Science and Technology) %J Chinese Astronomy and Astrophysics %V 12 %D 09/1988 %P 212 %L 215 %C (c) 1988 Elsevier Science B.V. All rights reserved. %I ABSTRACT: Abstract; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1988ChA&A..12..212W %B For ten supernova remnants containing single pulsars, their X-ray luminosity and surface brightness have been measured with the High Resolution Imager and the Imaging Proportional Counter on board Einstein satellite, resulting in an empirical relation between the X-ray luminosity and characteristic features of the pulsar. A preliminary investigation is also made on those remnants with central compact X-ray sources but no pulse signals. %Y DOI: 10.1016/0275-1062(88)90049-5 %R 1988slmc.proc..408H %T The X-ray environment of the precursor of SN 1987A. %A Harnden, F. R., Jr.; Seward, F. D. %J Supernova 1987A in the Large Magellanic Cloud %D 01/1988 %P 408 %L 410 %K Supernova 1987A in LMC, Supernovae:Progenitors, Supernovae:X Rays, X Rays:Supernovae %I CITATIONS: Citations to the Article; %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/1988slmc.proc..408H %R 1988srim.conf..115S %T X-Ray Images of Supernova Remnants %A Seward, F. D. %J IAU Colloq. 101: Supernova Remnants and the Interstellar Medium %D 01/1988 %P 115 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I TOC: Table of Contents; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %U https://ui.adsabs.harvard.edu/abs/1988srim.conf..115S %B Einstein observations of supernova remnants have been reviewed and analyzed. Images of 44 galactic remnants have been reprocessed, merged when necessary, and collected into a catalog. This paper gives an example and description of this catalog. %R 1988VA.....31..271W %T An X-ray investigation of crab-like supernova remnants %A Wang, Zhenru; Seward, F. D. %F AA(China Center of Advanced Science and Technology; Nanjing University, China), AB(Harvard Smithsonian Center for Astrophysics) %J Vistas in Astronomy %V 31 %D 01/1988 %P 271 %L 274 %K Crab Nebula, Energy Dissipation, Pulsars, Supernova Remnants, X Ray Astronomy, Energy Transfer, Milky Way Galaxy, Morphology, Astrophysics %C (c) 1988 Elsevier Science B.V. All rights reserved. %I ABSTRACT: Abstract; %I REFERENCES: References in the Article; %I TOC: Table of Contents; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1988VA.....31..271W %B Results are presented of an X-ray investigation of several Crab-like supernova remnants (SNRs), especially those with central pulsars. A statistical relationsip was obtained between the total X-ray luminosity of an isolated pulsar and its nebula in the 0.2-4.0 keV band and the rotating energy loss rate of the pulsar. The relationship strongly suggests that the energy source of X-rays both from an isolated pulsar and its nebula comes from the rotating energy loss of the pulsar, and that the energy transformation may be simple and direct. Data obtained on the surface brightness of a Crab-like SNR with a central compact source but with no pulsating signals, such as the 3C 58 SNR, show that the central part of this SNR coincides with that of a point source calibration. Reasons are suggested for the observation that some compact sources in Crab-like SNRs might not appear as pulsars. %Y DOI: 10.1016/0083-6656(88)90210-3 %R 1988mwa..work..235C %T Supernovae and supernova remnants. %A Chevalier, Roger A.; Seward, Frederick D. %F AA(University of Virginia), AB(Harvard Smithsonian Center for Astrophysics) %J Multiwavelength Astrophysics %D 01/1988 %P 235 %L 265 %K Stellar Spectra, Supernova Remnants, Supernovae, Hydrogen, Light Curve, Line Spectra, Pulsars, Spectrum Analysis, Astrophysics, Pulsars:Supernovae, Supernova Remnants, Supernovae, Supernovae:Pulsars %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/1988mwa..work..235C %B Contents: 1. Introduction. 2. Observations of supernovae: Type Ia supernovae. Type Ib supernovae. Type II supernovae. 3. Interpretation and future prospects: Shock heating by the initial explosion. Radioactive energy input. Circumstellar interaction. Pulsar energy input. 4. Supernova remnants: Tycho's remnant (2.5 kpc distant, 415 years old). Kepler's remnant (4 kpc distant, 383 years old). The Cygnus Loop (0.8 kpc distant, ≡15,000 years old). Puppis A (2 kpc distant, 3700 years old). The Crab Nebula (2 kpc distant, 933 years old). Pulsars. 5. Summary. %R 1988LNP...305..452W %T An X-Ray Investigation of Crab-Like Supernova Remnants %A Wang, Z. R.; Seward, F. D. %J IAU Colloq. 108: Atmospheric Diagnostics of Stellar Evolution %V 305 %D 01/1988 %P 452 %I Co-Reads: Co-Reads; %I TOC: Table of Contents; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1988LNP...305..452W %Y DOI: 10.1007/BFb0034648 %R 1987BAAS...19.1076V %T Survey of Column Densities to Galactic X-ray Sources Using the Einstein OGS %A Vrtilek, S. D.; Wargelin, B. J.; McClintock, J. E.; Kahn, S. M.; Seward, F. D. %J Bulletin of the American Astronomical Society %V 19 %D 09/1987 %P 1076 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1987BAAS...19.1076V %R 1987IAUS..125...99S %T Neutron Stars in Twelve Supernova Remnants %A Seward, Frederick D. %F AA(Harvard Smithsonian Center for Astrophysics) %J The Origin and Evolution of Neutron Stars %V 125 %D 01/1987 %P 99 %K Binary Stars, Neutron Stars, Stellar Coronas, Stellar Rotation, Supernova Remnants, X Ray Astronomy, Charged Particles, Gravitational Collapse, Magnetic Fields, Pulsars, Red Giant Stars, Synchrotron Radiation, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I TOC: Table of Contents; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %U https://ui.adsabs.harvard.edu/abs/1987IAUS..125...99S %B X-ray observations of selected SNR are summarized. Five contain internal spinning neutron stars - four isolated and one in a binary system. Another seven contain central unresolved sources or bright nebulae. Observations of these nebulae, probably due to synchrotron emission, are used to estimate characteristics of the unseen pulsars. %R 1986ApJ...308..644V %T X-Ray Emission Lines from Three Galactic Bulge Sources %A Vrtilek, S. D.; Helfand, D. J.; Halpern, J. P.; Kahn, S. M.; Seward, F. D. %F AA(NASA Goddard Space Flight Center, Maryland; Columbia University, New York), AB(Columbia University, New York), AC(Columbia University, New York), AD(University of California, Berkeley), AE(Harvard Smithsonian Center for Astrophysics) %J The Astrophysical Journal %V 308 %D 09/1986 %P 644 %K Astronomical Spectroscopy, Emission Spectra, Galactic Bulge, Globular Clusters, Line Spectra, Milky Way Galaxy, X Ray Binaries, Astronomical Models, Black Body Radiation, Bremsstrahlung, Galactic Structure, Heao 2, Spaceborne Astronomy, Astrophysics, X-RAYS: BINARIES, X-RAYS: BURSTS %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1986ApJ...308..644V %B The globular cluster burst source 1820-30 (NGC 6624), the burster Serpens X-1, and the bulge source GX 9+9 were each observed simultaneously with the Einstein objective grating spectrometer and monitor proportional counter. In the high-resolution grating data emission features attributable to highly ionized states of O, N, Fe, and possibly Si and S are present. The relative intensities of these features are rather poorly described by existing models of the X-ray emitting gas in compact systems. All three sources have broad-band X-ray spectra that are well fitted by either of two models: single thermal bremsstrahlung spectra with temperatures of ≡6 - 10 keV, or two-component blackbody spectra with temperatures of 0.5 - 0.7 keV and ≡2.0 keV. %H IOP %Y DOI: 10.1086/164535 %R 1986ApJ...307..698V %T Spectral Variability of Cygnus X-2: Structure in the Circumsource Material %A Vrtilek, S. D.; Kahn, S. M.; Grindlay, J. E.; Helfand, D. J.; Seward, F. D. %F AA(NASA Goddard Space Flight Center, Maryland; Columbia University, New York), AB(University of California, Berkeley), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics), AE(Columbia University, New York) %J The Astrophysical Journal %V 307 %D 08/1986 %P 698 %K Stellar Spectra, Variable Stars, X Ray Binaries, Black Body Radiation, Broadband, Companion Stars, Neutron Stars, Spectral Energy Distribution, Astrophysics, RADIATION MECHANISMS, STARS: INDIVIDUAL CONSTELLATION NAME: CYGNUS X-2, X-RAYS: BINARIES %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1986ApJ...307..698V %B Cygnus X-2 was observed during 13 separate pointings in the course of 1 yr by the Einstein monitor proportional counter. During one of these pointings the objective grating spectrometer was also used. It is found that the data from these observations are well fitted by single-component thermal bremsstrahlung models with temperatures ranging from 4-12 keV; however, two-component models, where one component is a blackbody, are not excluded. The X-ray light curve appears to be correlated with the 9.843 day optical period, possibly implying a partial eclipse of the X-ray source. During the high states there are irregular dips of up to 30 percent in intensity that last for 300-700 s. The high spectra resolution grating data were taken during one of the high states when these dips occurred, and it is possible to distinguish variable variable emission and absorption features due to Fe, O, and Ne. The picture of Cygnus X-2 is consistent with an intrinsic thermal source surrounded by a hot accretion disk corona. This model can be used to explain the high and low X-ray states, the variability within the states, and the intensity dips which occur in the high states. %H IOP %Y DOI: 10.1086/164455 %R 1986ApJ...305..814S %T A 6 Second Periodic X-Ray Source in Carina %A Seward, F. D.; Charles, P. A.; Smale, A. P. %F AA(Harvard Smithsonian Center for Astrophysics), AB(University of Oxford, UK) %J The Astrophysical Journal %V 305 %D 06/1986 %P 814 %K B Stars, Variable Stars, X Ray Binaries, Exosat Satellite, X Ray Spectra, Astrophysics, STARS: BE, STARS: INDIVIDUAL ALPHANUMERIC: 1E 1048.1-5937, X-RAYS: BINARIES, X-RAYS: SOURCES %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1986ApJ...305..814S %B A serendipitous source, 1E 1048.1-5937, was discovered during Einstein imaging observations of the Carina nebula. On July 13, 1979, this source had an intensity of 0.14 IPC counts/s, and the signal was 65 percent pulsed with a period of 6.44 s. An earlier observation failed to detect any source with strength greater than 1/10 the above signal. The source is therefore highly variable, perhaps transient. An Exosat observation of this source on June 20, 1985 confirmed the pulse period and refined the source position to an accuracy of 10 arcsec. On the basis of the position, the source is tentatively identified with a V = 19 optical counterpart. The X-ray spectrum is best fitted by a power law with photon index = 2.26 and a column density of 1.6 x 10 to the 22nd atoms/sq cm. The X-ray characteristics are consistent with an accretion-powered Be star binary. %H IOP %Y DOI: 10.1086/164294 %R 1986S&T....71....6S %T Neutron Stars in Supernova Remnants %A Seward, F. D. %F AA(Harvard Smithsonian Center for Astrophysics) %J Sky and Telescope %V 71 %D 01/1986 %P 6 %K Magellanic Clouds, Neutron Stars, Supernova Remnants, X Ray Spectra, Interstellar Matter, Nebulae, Pulsars, Stellar Magnetic Fields, Astrophysics %I ABSTRACT: Abstract; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %U https://ui.adsabs.harvard.edu/abs/1986S&T....71....6S %B Present knowledge and recent findings on neutron stars in supernova remnants (SNRs) are reviewed. The physics of the production of neutron stars by supernova explosions is briefly summarized, and the well-known Crab Nebula and Vela X SNRs are described. Three new discoveries of neutron stars associated with SNRs in the Galaxy and the Magellanic Clouds are discussed. These discoveries support a model of Crablike remnants which assumes that the pulsar is surrounded by two envelopes: an outer shell of fast-moving material thrown out by the supernova and a more slowly moving layer of matter from its core. %R 1986ApJ...300..453G %T An Upper Limit to X-Ray Emission from Saturn %A Gilman, D. A.; Hurley, K. C.; Seward, F. D.; Schnopper, H. W.; Sullivan, J. D.; Metzger, A. E. %F AA(NASA HQ), AB(Centre d'Étude Spatiale des Rayonnements, Toulouse, France), AC(Smithsonian Astrophysical Observatory), AD(DTU Physics, Lyngby), AE(Massachusetts Institute of Technology), AF(Jet Propulsion Laboratory) %J The Astrophysical Journal %V 300 %D 01/1986 %P 453 %K Auroral Arcs, Heao 2, Planetary Radiation, Saturn (Planet), Saturn Atmosphere, X Ray Sources, Bremsstrahlung, Energy Transfer, Pioneer 11 Space Probe, Planetary Magnetospheres, Ultraviolet Astronomy, X Ray Spectra, SATURN, X-RAYS, EMISSIONS, MAGNETOSPHERE, PIONEER 11, ULTRAVIOLET, WAVELENGTHS, VOYAGER MISSIONS, SPACECRAFT OBSERVATIONS, SOURCE, Lunar and Planetary Exploration; Saturn, PLANETS: SATURN, X-RAYS: SOURCES %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1986ApJ...300..453G %B X-rays are produced in auroral discharges, and their measurement can serve to characterize the interaction processes responsible for the aurora itself. The existence of auroral activity on Saturn was suggested by the observation of a magnetosphere by Pioneer 11 and confirmed by UV measurements during the Voyager encounters. The detection of X-rays from Jupiter with the Einstein Observatory (HEAO 2) satellite provided the impetus for a subsequent observation of Saturn. No emission was detected. This article presents the upper limit established by the observation and derives an expected emission level assuming X-ray production to be the result of bremsstrahlung from keV electrons precipitating into Saturn's atmosphere. The difference is a factor of 100. %H IOP %Y DOI: 10.1086/163820 %R 1985ApJ...299..821K %T EINSTEIN observations of the VELA supernova remnant : the spatial structure of the hot emitting gas. %A Kahn, S. M.; Gorenstein, P.; Harnden, F. R., Jr.; Seward, F. D. %F AA(University of California, Berkeley), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics) %J The Astrophysical Journal %V 299 %D 12/1985 %P 821 %L 827 %K Heao 2, Nebulae, Supernova Remnants, X Ray Sources, X Ray Spectra, Spectrum Analysis, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1985ApJ...299..821K %B Spatially resolved (aproximately 1 arcmin) X-ray maps of the Vela supernova remnant have been constructed in two spectral bands, 0.2-1.0 keV and 0.8-2.0 keV, from a series of 36 separate observations with the Imaging Proportional Counter of the Einstein Observatory. The maps exhibit substantial structure on all angular scales. Spectral analysis shows that the emission from the remnant can be consistently described as thermal radiation from hot gas which is nonuniform in density and temperature, but which is in approximate pressure equilibrium. It is found that p/k is approximately 3-4 x 10 to the 5th/cu cm K. The soft X-ray emission exhibits a high degree of correlation with the optical filamentary structure, in the sense that the most prominent filaments either tightly surround or are coincident with the brightest X-ray regions. This suggests that the softest X-radiation may originate in 'warm' gas which is evaporated from the denser clouds responsible for the optical and ultraviolet filaments. Such an interpretation is quantitatively investigated, and shown to be only marginally consistent with the observations. %H IOP %Y DOI: 10.1086/163748 %R 1985ApJ...299..828H %T Einstein observations of VELA X and the VELA pulsar. %A Harnden, F. R., Jr.; Grant, P. D.; Seward, F. D.; Kahn, S. M. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(University of California, Berkeley) %J The Astrophysical Journal %V 299 %D 12/1985 %P 828 %L 838 %K Heao 2, Nebulae, Neutron Stars, Pulsars, Supernova Remnants, X Ray Sources, Morphology, Stellar Temperature, Surface Temperature, Thermal Emission, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1985ApJ...299..828H %B The imaging detectors of the Einstein X-ray observatory have been used to study the Vela pulsar and its surrounding region. Although the pulsar is a relatively strong source of X-rays, there are not detectable pulsations at the pulsar period; the pulsed X-ray luminosity is less than approximately 10 to the 31st ergs/s in the 0.1-4.5 keV band. Nor is there evidence for other types of variability in the pulsar's X-ray emission. The images reveal structure on four spatial scales: (1) a pointlike object coincident with the pulsar; (2) a relatively bright, approximately 4-arcmin nebula of diffuse emission about the pulsar; (3) an approximately 1-degree nebula of hard emission that lies between the pulsar and the radio feature Vela X; and (4) thermal emission from the entire approximately 5-degree Vela supernova remnant. Spectral data from the small nebula are well fitted by a synchrotron model. Under the assumption that emission from the pulsar itself is thermal blackbody radiation, the surface temperature of the neutron star is calculated to be 1 million K. %H IOP %Y DOI: 10.1086/163749 %R 1985MNRAS.217...99S %T X-ray observations of the supernova remnant W 44. %A Smith, A.; Jones, L. R.; Watson, M. G.; Willingale, R.; Wood, N.; Seward, F. D. %F AA(University of Leicester, UK), AB(University of Leicester, UK), AC(University of Leicester, UK), AD(University of Leicester, UK), AE(University of Leicester, UK) %J Monthly Notices of the Royal Astronomical Society %V 217 %D 11/1985 %P 99 %L 104 %K Astronomical Models, Radio Sources (Astronomy), Supernova Remnants, X Ray Sources, Heao 2, Interstellar Matter, Molecular Clouds, Plasma Temperature, X Ray Spectra, Astronomy %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I PUB_HTML: Publisher Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1985MNRAS.217...99S %B The authors present Einstein Observatory X-ray observations of the supernova remnant W44 (G34.7-0.4). The X-ray morphology is centrally peaked and shows an anti-correlation with the radio shell. X-ray spectral data indicate a temperature for the emitting plasma of approximately 1 keV. The authors suggest a model for W44 in which the remnant is in its late adiabatic phase. The soft X-ray shell has become too cool to be observable through the intervening ISM, yet a hotter interior remains visible. W44 would then appear to fit in reasonably well with the generally accepted evolution of shell-like remnants and a Crab-like component is not required to explain the X-ray morphology. %H OUP %Y DOI: 10.1093/mnras/217.1.99 %R 1985BAAS...17..883P %T The X-Ray Structure and Spectrum of IC 443 %A Petre, R.; Szymkowiak, A. E.; Seward, F. D.; Canizares, C. R.; Willingale, R.; Rolf, D.; Woods, N. %J Bulletin of the American Astronomical Society %V 17 %D 09/1985 %P 883 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1985BAAS...17..883P %R 1985SciAm.253b..88S %T Young supernova remnants. %A Seward, F. D.; Gorenstein, P.; Tucker, W. H. %F AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory), AC(Smithsonian Astrophysical Observatory; University of California, Irvine) %J Scientific American %V 253 %D 08/1985 %P 88 %L 96 %K Heao 2, Pulsars, Stellar Mass Accretion, Supernova Remnants, X Ray Sources, X Ray Telescopes, Crab Nebula, Events, Radio Astronomy, Shock Waves, Star Clusters, Synchrotron Radiation, Astrophysics, Pulsars:Supernova Remnants, Supernova Remnants:Pulsars, Supernova Remnants:X-Ray Sources, X-Ray Sources:Supernova Remnants %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1985SciAm.253b..88S %B The remnants of recent stellar explosions in our galaxy are intense X-ray sources. An orbiting telescope has revealed their structure. One has a pulsar; others are expanding shells of shock-heated gas. %Y DOI: 10.1038/scientificamerican0885-88 %R 1985ComAp..11...15S %T Supernova remnants containing neutron stars. %A Seward, F. D. %F AA(Harvard Smithsonian Center for Astrophysics) %J Comments on Astrophysics %V 11 %D 08/1985 %P 15 %L 51 %K Neutron Stars, Supernova Remnants, X Ray Astronomy, Binary Stars, Crab Nebula, Gravitational Collapse, Pulsars, Radio Sources (Astronomy), Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %U https://ui.adsabs.harvard.edu/abs/1985ComAp..11...15S %B X-ray observations of Crab Nebula-like supernova remnants are summarized. Five remnants are found to contain internal neutron stars - four isolated and one in a binary system. Another five remnants have central unresolved X-ray sources which are probably neutron stars. Thus approximately 10 remnants are now known to have their origin in gravitational collapse. Another 22 remnants show some Crab-like properties, but the existence of a central compact object or pulsar is doubtful or unconfirmed. The four fast isolated pulsars in SNR are also compared with five X-ray detected radio pulsars. %R 1985IAUC.4083....3S %T 1E 1048.1-5937 %A Smale, A. P.; Charles, P. A.; Corbet, R. H. D.; Seward, F. D. %J International Astronomical Union Circular %V 4083 %D 07/1985 %P 3 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I PUB_HTML: Publisher Article; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1985IAUC.4083....3S %B A. P. Smale, P. A. Charles and R. H. D. Corbet, Oxford University; and F. D. Seward, Center for Astrophysics, report: "We have performed an EXOSAT observation of the Einstein x-ray pulsar 1E 1048.1-5937 (Seward and Charles 1984, Bull. A.A.S. 16, 983) lasting 6.5 hr on June 20. From the medium-energy experiment we confirm the presence of x-ray pulsations at a period of 6.4407 +/- 0.0009 s, which is slightly but significantly longer than the Einstein value. The best fit to the x-ray spectrum is a power law with photon index 2.3 and, when combined with the observed countrate in the low-energy telescopes, it indicates a high degree of obscuration (~ 1.6 x 10**26 atoms m**-2). The source position is R.A. = 10h48m10s05, Decl. = -59deg37'24" 9 (equinox 1950.0) with an error-circle radius of 15". Examination of SRC IIIa-J and ESO blue plates reveals that the brightest star in this circle has V ~ 19. The x- ray obscuration implies a visual extinction Av ~ 8, and hence this system can be interpreted as a distant Be binary." %R 1985BAAS...17..590V %T High-Resolution X-ray Spectroscopy of Three Galactic Bulge Sources %A Vrtilek, S. D.; Chanan, G. A.; Helfand, D. J.; Kahn, S. M.; Seward, F. D. %J Bulletin of the American Astronomical Society %V 17 %D 03/1985 %P 590 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1985BAAS...17..590V %R 1985cnrs.work..203H %T The X-ray morphology of the Vela X region. %A Harnden, F. R., Jr.; Grant, P. D.; Seward, F. D. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics) %J The Crab Nebula and Related Supernova Remnants %D 01/1985 %P 203 %L 209 %K Emission Spectra, Pulsars, Radio Sources (Astronomy), Spectral Energy Distribution, Supernova Remnants, X Ray Spectra, Brightness Distribution, Diffuse Radiation, Heao 2, Point Sources, Spaceborne Astronomy, Spectrum Analysis, Astrophysics, Pulsars:Supernova Remnants, Supernova Remnants:Pulsars, Supernova Remnants:X-Ray Maps, X-Ray Maps:Supernova Remnants %I ABSTRACT: Abstract; %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/1985cnrs.work..203H %B Further analysis of Einstein Observatory images of the Vela pulsar has revealed additional detail in the X-ray emission of the central region of the Vela supernova remnant. Components previously reported from the Einstein data are: (1) filaments within the approximately 5-degree remnant; (2) a reasonably strong (approximately 1.7 ct/sec) point-like source coincident with the pulsar; and (3) a cloud of diffuse emission about the pulsar position. Image processing of IPC data has now revealed a region of lower surface brightness emission extending as far as about 1 degree, primarily to the south of the pulsar and in the direction of the radio emission maximum known as Vela X. %R 1985PhT....38R...8S %T A new fast X-ray pulsar. %A Seward, F. D. %J Physics Today %V 38 %D 01/1985 %P S8 %K X-Ray Pulsars %U https://ui.adsabs.harvard.edu/abs/1985PhT....38R...8S %R 1985xra..conf..297S %T Discovery of a 50 msec pulsar in the Large Magellanic Cloud. %A Seward, F. D.; Harnden, F. R., Jr.; Helfand, D. J. %J X-ray Astronomy 1984 %D 01/1985 %P 297 %L 300 %K Magellanic Clouds:X-Ray Pulsars, X-Ray Pulsars:Magellanic Clouds %I ABSTRACT: Abstract; %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/1985xra..conf..297S %B The authors report here the discovery of a new pulsed X-ray source in the Large Magellanic Cloud supernova remnant 0540-693 that, in many ways, is remarkably similar to the Crab Nebula. %R 1985cnrs.work..165S %T The 50 millisecond pulsar in the Large Magellanic Cloud and the X-raypulse emission mechanism. %A Seward, F. D.; Harnden, F. R., Jr.; Elsner, R. F. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(NASA Marshall Space Flight Center) %J The Crab Nebula and Related Supernova Remnants %D 01/1985 %P 165 %L 171 %K Emission Spectra, Magellanic Clouds, Pulsars, Stellar Physics, Supernova Remnants, X Ray Spectra, Crab Nebula, Spectral Energy Distribution, Stellar Luminosity, Stellar Spectrophotometry, Synchrotron Radiation, Astrophysics, Magellanic Clouds:Pulsars, Pulsars:Magellanic Clouds, Pulsars:Supernova Remnants, Supernova Remnants:Pulsars, X-Ray Luminosities:X-Ray Pulsars, X-Ray Pulsars:X-Ray Luminosities %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I Co-Reads: Co-Reads; %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/1985cnrs.work..165S %B PSR 0540-69 is embedded in a supernova remnant which, as new observations are made, increasingly shows properties similar to those of the Crab Nebula. The relative pulsed counting rates in the Einstein IPC and MPC detectors determine a spectral index which bears directly on the pulse emission mechanism. A non-thermal mechanism is indicated. %R 1984ApJ...287L..19S %T Discovery of a 50 millisecond pulsar in the Large Magellanic Cloud. %A Seward, F. D.; Harnden, F. R., Jr.; Helfand, D. J. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Columbia University, New York) %J The Astrophysical Journal %V 287 %D 12/1984 %P L19 %L L22 %K Magellanic Clouds, Pulsars, Supernova Remnants, X Ray Sources, Crab Nebula, Galactic Radiation, Nebulae, Pulse Duration, Pulsed Radiation, Astronomy, Magellanic Clouds:Supernova Remnants, Magellanic Clouds:X-Ray Pulsars, Supernova Remnants:Magellanic Clouds, Supernova Remnants:X-Ray Pulsars, X-Ray Pulsars:Magellanic Clouds, X-Ray Pulsars:Supernova Remnants %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %U https://ui.adsabs.harvard.edu/abs/1984ApJ...287L..19S %B The authors have discovered a 50 ms X-ray pulsar in the Crab-like LMC supernova remnant 0540-693. The pulsar is spinning down with P= 4.79×10^-13s s^-1, implying a characteristic age of 1660 yr and an energy loss rate of E= 1.5×10³⁸ergs s^-1, one-third that of the Crab pulsar. The X-ray luminosity of the surrounding nebula is L_X ≈ 10³⁷ergs s^-1. Unlike the Crab, the X-ray pulse shape is approximately sinusoidal with one broad maximum per period, and the ratio of pulsed luminosity (in the range 0.2 - 0.4 keV) to Eis an order of magnitude greater than that of the Crab pulsar. %H IOP %Y DOI: 10.1086/184388 %R 1984IAUC.4001....2S %T 2S 0142+61 %A Seward, F. %J International Astronomical Union Circular %V 4001 %D 10/1984 %P 2 %I ABSTRACT: Abstract; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1984IAUC.4001....2S %B The following remarks should have been included in the item by White et al. on IAUC 3996: "The EXOSAT CMA 10" error circle is centered at R.A. = 1h42m52s9, Decl. = +61deg29'49" (equinox 1950.0), and overlaps the Einstein HRI position (obtained from the Einstein data base) of R.A. = 1h42m53s7, Decl. = +61deg30'05". F. Seward notes that the 90-percent-confidence random uncertainty in the Einstein position is 3", but this particular position may have an additional systematic offset of 5". Using the star numbering convention of Reid et al. (1980, A.J. 85, 1062), we note that star 3 lies 10" and 18", and that star 8 lies 8" and 12", respectively, from the centers of the EXOSAT and Einstein HRI error circles." %R 1984ApJ...285..607W %T An X-ray investigation of the unusual supernova remnant CTB 80. %A Wang, Z. R.; Seward, F. D. %F AA(Nanjing University, China; Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics) %J The Astrophysical Journal %V 285 %D 10/1984 %P 607 %L 612 %K Nebulae, Satellite Observation, Supernova Remnants, X Ray Astronomy, X Ray Sources, Astronomical Maps, Luminosity, X Ray Imagery, Astronomy %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1984ApJ...285..607W %B The X-ray properties of SNR CTB 80 (G68.8 + 2.8) are discussed based on both low- and high-resolution images from the Einstein satellite. The X-ray maps show a point source coinciding with the region of maximum radio emission. Diffuse X-ray emission is evident mainly along the radio lobe extending about 8 arcmin east of the point source and aligned with the projected magnetic field lines. The observed X-ray luminosity is 3.2 x 10 to the 34th ergs/s with 1.0 x 10 to the 3th ergs/s from the point source (assuming a distance of 3 kpc). There is also faint, diffuse, X-ray emission south of the point source, where radio emission is absent. The unusual radio and X-ray morphologies are interpreted as a result of relativistic jets energized by the central object, and the possible association of CTB 80 with SN 1408 as recorded by Chinese observers is discussed. %H IOP %Y DOI: 10.1086/162536 %R 1984BAAS...16Q.983S %T A Six-Second Periodic X-ray Source in Carina %A Seward, F. D.; Charles, P. A. %J Bulletin of the American Astronomical Society %V 16 %D 09/1984 %P 983 %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1984BAAS...16Q.983S %R 1984ApJ...283..279H %T Einstein observations of the Crab Nebula pulsar. %A Harnden, F. R., Jr.; Seward, F. D. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics) %J The Astrophysical Journal %V 283 %D 08/1984 %P 279 %L 285 %K Crab Nebula, Pulsars, X Ray Sources, Heao 2, Light Curve, Spatial Distribution, Temporal Distribution, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1984ApJ...283..279H %B Einstein Observatory (HEAO 2) high-resolution (approximately 4 sec) images of the Crab nebula which clearly resolve the pulsar from the diffuse X-ray emission are presented. The pulsar contributes 3.9 + or - 0.2 percent of the observed 0.1-4.5 keV flux and shows no evidence (other than the 33 ms pulsations) for variations on time scales up to approximately 2.3 days. The pulsar flux decreases to zero over about one-eighth of the cycle, with the upper limit to point source emission during this interval implying a blackbody surface temperature of less than 2.5 x 10 to the 6th K for the neutron star (10 km assumed radius). The spatial distribution of nebular emission near the pulsar closely resembles that of the optical continuum. %H IOP %Y DOI: 10.1086/162304 %R 1984ApJ...283..286K %T High-resolution soft X-ray spectra of Scorpius X-1 : the structure ofcircumsource accreting material. %A Kahn, S. M.; Seward, F. D.; Chlebowski, T. %F AA(Columbia University, New York; University College London, UK), AB(Harvard Smithsonian Center for Astrophysics), AC(Nicolaus Copernicus Astronomical Center, Warsaw; Harvard Smithsonian Center for Astrophysics) %J The Astrophysical Journal %V 283 %D 08/1984 %P 286 %L 294 %K Binary Stars, Stellar Mass Accretion, Stellar Spectra, X Ray Stars, Abundance, Calibrating, High Resolution, Spectrum Analysis, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1984ApJ...283..286K %B Four observations of Scorpius X-1 with the Objective Grating Spectrometer of the Einstein Observatory have provided high-resolution spectra (lambda/Delta lambda = approximately 20-50) in the wavelength range 7-46 A. The spectra reveal the presence of absorption structure due to oxygen, nitrogen, and iron, and variable emission structure associated with ionized iron and nitrogen. The strengths of these features suggest that the N/O abundance ratio in the absorbing and line emitting gas is anomalously high, which might indicate that these spectral components are associated with processed material, probably accreting matter transferred from the surface of an evolved companion. Constraints on the inclination of the system, however, imply that this cool, dense, accreting material must be well out of the plane of the binary system. Possible models for the origin and nature of this circumsource medium are discussed. An extensive discussion of the calibration of the Objective Grating Spectrometer and of the analysis of spectra acquired by that instrument is also provided. %H IOP %Y DOI: 10.1086/162305 %R 1984ApJ...281..665C %T X-rays from eta Carinae. %A Chlebowski, T.; Seward, F. D.; Swank, J.; Szymkowiak, A. %F AA(University of Warsaw, Department of Astronomy), AB(Harvard Smithsonian Center for Astrophysics), AC(NASA Goddard Space Flight Center, Maryland), AD(NASA Goddard Space Flight Center, Maryland) %J The Astrophysical Journal %V 281 %D 06/1984 %P 665 %L 672 %K Nebulae, Stellar Envelopes, Variable Stars, X Ray Sources, Astronomical Maps, Morphology, Spectral Energy Distribution, Stellar Models, X Ray Spectroscopy, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1984ApJ...281..665C %B X-ray observations of Eta Car obtained with the high-resolution imager and solid-state spectrometer of the Einstein observatory are reported and interpreted in terms of a two-shell model. A soft component with temperature 5 million K is located in the expanding outer shell, and the hard core component with temperature 80 million K is attributed to the interaction of a high-velocity stellar wind from the massive central object with the inner edge of a dust shell. Model calculations based on comparison with optical and IR data permit estimation of the mass of the outer shell (0.004 solar mass), the mass of the dust shell (3 solar mass), and the total shell expansion energy (less than 2 x 10 to the 49th ergs). %H IOP %Y DOI: 10.1086/162143 %R 1984ApJ...281..650S %T The X-ray nebula around PSR 1509-58. %A Seward, F. D.; Harnden, F. R., Jr.; Szymkowiak, A.; Swank, J. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(NASA Goddard Space Flight Center, Maryland), AD(NASA Goddard Space Flight Center, Maryland) %J The Astrophysical Journal %V 281 %D 06/1984 %P 650 %L 657 %K Nebulae, Pulsars, Supernova Remnants, Synchrotron Radiation, X Ray Sources, Crab Nebula, Luminosity, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1984ApJ...281..650S %B With the use of measured spectra and a model, volumes and luminosities are derived for several components of the supernova remnant MSH 15 - 52. The hard, featureless spectrum and spatial symmetry of the X-ray nebula surrounding the central pulsar strongly indicate synchrotron radiation as the source of emission. Power requirements are easily supplied by the pulsar. The observed surface brightness is only 0.00002 that of the X-ray synchrotron emission around the Crab pulsar, and the X-ray luminosity is 0.01 that of the Crab. In spite of the great difference in luminosity and size, the two systems are probably similar in nature, with the high brightness and unique appearance of the Crab synchrotron nebula being due to the high energy output of the pulsar and the relatively small volume of the confining filaments. %H IOP %Y DOI: 10.1086/162141 %R 1984MNRAS.207..649P %T Radio and X-ray maps of the supernova remnant W 49B. %A Pye, J. P.; Becker, R. H.; Seward, F. D.; Thomas, N. %F AA(University of Leicester, UK), AB(University of Leicester, UK), AC(Virginia Polytechnic Institute and State University), AD(Harvard Smithsonian Center for Astrophysics) %J Monthly Notices of the Royal Astronomical Society %V 207 %D 04/1984 %P 649 %L 657 %K Astronomical Maps, Radio Sources (Astronomy), Supernova Remnants, X Ray Sources, Brightness Distribution, Centimeter Waves, Spaceborne Astronomy, Spatial Distribution, Astronomy %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1984MNRAS.207..649P %B New high resolution radio maps of the supernova remnant (SNR) W49B at 6 and 20 cm are presented, together with soft X-ray maps representing the first detection of the SNR in X-rays. The source is also detected in the medium energy X-ray band. The radio maps have a resolution of about 12 arcsec and show that the emission is distributed in an incomplete shell of radius about 100 arcsec, with intense ridges in the west and east. There is no indication of significant spectral variations between 6 and 20 cm and no significant polarization is detected. The X-ray map shows emission which is clearly extended and increases in intensity toward the center of the radio remnant, with no evidence for limb brightening. The X-ray surface brightness distribution falls to half peak value at about 75 arcsec radius. There is no evidence for a pointlike X-ray source. %H OUP %Y DOI: 10.1093/mnras/207.3.649 %R 1984ApJ...279..705W %T X-rays from the SNR 3C 391. %A Wang, Z. R.; Seward, F. D. %F AA(Harvard Smithsonian Center for Astrophysics) %J The Astrophysical Journal %V 279 %D 04/1984 %P 705 %L 707 %K Supernova Remnants, X Ray Sources, Heao 2, Luminosity, Radio Sources (Astronomy), Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1984ApJ...279..705W %B An X-ray map and spectral information were obtained from a short Einstein observation of 3C 391 (G31.9+0.0). Both X-ray and radio emission appear to come from an irregular shell ≡5arcmin in diameter. For a distance of 11 kpc the X-ray luminosity is at least 10³⁵ ergs s^-1. The luminosity, the radius, and the temperature are about as expected from a middle-aged SNR expanding into a medium with density a few tenths of an atom cm^-3. %H IOP %Y DOI: 10.1086/161935 %R 1984BAAS...16..542H %T Period Behavior of the New LMC Pulsar %A Harnden, F. R., Jr.; Seward, F. D. %J Bulletin of the American Astronomical Society %V 16 %D 03/1984 %P 542 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1984BAAS...16..542H %R 1984BAAS...16..471V %T Dramatic Variability in the X-Ray Flux of Hercules X-1 Preceding the Binary Eclipse %A Vrtilek, S. D.; Kahn, S. M.; Seward, F. D.; Grindlay, J. E. %J Bulletin of the American Astronomical Society %V 16 %D 03/1984 %P 471 %I CITATIONS: Citations to the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1984BAAS...16..471V %R 1984IAUC.3928....2S %T X-Ray Pulsar in Large Magellanic Cloud %A Seward, F. D.; Harnden, F. R., Jr.; Helfand, D. %J International Astronomical Union Circular %V 3928 %D 03/1984 %P 2 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I PUB_HTML: Publisher Article; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1984IAUC.3928....2S %B F. D. Seward and F. R. Harnden, Jr., Harvard-Smithsonian Center for Astrophysics; and D. Helfand, Columbia Astrophysical Laboratory, report the discovery of an x-ray pulsar within or close to the Crab-like supernova remnant 0540-69.3 in the LMC. Pulsations were detected in four separate observations with the Einstein Observatory IPC. On 1979 Sept. 8.01 UT the barycentric period was 50.206102 +/- 0.000040 ms, and the period derivative measured during 1979 Apr. 11-Nov. 11 was 41.8 +/- 0.2 ns/day. Comparison with the Crab and Vela pulsars suggests that radio detection should be possible and that optical pulsations may also be observable. %R 1984BAAS...16..542S %T A 50-Millisecond Crab-like Pulsar in the Large Magellanic Cloud %A Seward, F. D.; Harnden, F. R., Jr.; Helfand, D. J. %J Bulletin of the American Astronomical Society %V 16 %D 03/1984 %P 542 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %U https://ui.adsabs.harvard.edu/abs/1984BAAS...16..542S %R 1984ApJ...277..286G %T The central X-ray source in SS 433. %A Grindlay, J. E.; Band, D.; Seward, F.; Leahy, D.; Weisskopf, M. C.; Marshall, F. E. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(NASA Marshall Space Flight Center), AD(NASA Marshall Space Flight Center), AE(NASA Goddard Space Flight Center, Maryland) %J The Astrophysical Journal %V 277 %D 02/1984 %P 286 %L 295 %K Binary Stars, Black Holes (Astronomy), X Ray Sources, Accretion Disks, Angular Momentum, Bremsstrahlung, Companion Stars, Heao 2, Stellar Flares, Stellar Luminosity, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1984ApJ...277..286G %B Numerous observations of SS 433 were obtained with the Einstein X-ray Observatory over an 18 month period from 1979 March through 1980 October. MPC (as well as imaging) data from these observations show that the central object in SS 433 is variable in intensity and spectrum on a wide range of time scales. Flares appear to be correlated with the 13 day binary period, and may be more numerous at particular phases of the 164 day period. No evidence for variability on time scales less than 5 minutes is seen, suggesting the central X-ray source is extended and that the compact object itself is not directly visible. A model for SS 433 is suggested wherein the companion star has a spin misaligned with the orbital angular momentum. The volume of the Roche lobe reaches a minimum twice per binary orbit, giving rise to enhanced accretion which results in X-ray and radio flares. Additional constraints imposed by the X-ray and optical data suggest the compact object in SS 433 is an approximately 10-solar-mass black hole. %H IOP %Y DOI: 10.1086/161695 %R 1984PhST....7..115H %T The high resolution soft X-ray spectrum of AM Herculis. %A Heise, J.; Kruszewski, A.; Chlebowski, T.; Mewe, R.; Kahn, S.; Seward, F. D. %F AA(Netherlands Institute for Space Research), AB(Netherlands Institute for Space Research), AC(University of Warsaw, Department of Astronomy), AD(University of Warsaw, Department of Astronomy), AE(Harvard Smithsonian Center for Astrophysics), AF(Harvard Smithsonian Center for Astrophysics) %J Physica Scripta Volume T %V 7 %D 01/1984 %P 115 %L 117 %K Binary Stars, Light Curve, Magnetic Stars, White Dwarf Stars, X Ray Spectra, Black Body Radiation, Heao 2, Ultraviolet Radiation, Astrophysics, AM Herculis:X-Ray Spectra, X-Ray Spectra:AM Herculis %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1984PhST....7..115H %B The authors present a high resolution (λ/Δλ = 80) soft X-ray spectrum (44 - 95 Å) of the magnetic white dwarf binary AM Her obtained with the Objective Grating Spectrometer on board the Einstein Observatory. Black body fits to the continuum strongly limit the range of allowable parameters and indicate a "color" temperature in the soft X-ray range between 40 and 55 eV. %Y DOI: 10.1088/0031-8949/1984/T7/026 %R 1984ASNYN...2....7H %T A new Crab-like pulsar in the Large Magellanic Cloud. %A Helfand, D. J.; Seward, F. D.; Harnden, F. R. %J News Letter of the Astronomical Society of New York %V 2 %D 01/1984 %P 7 %L 8 %K Magellanic Clouds:Pulsars, Period Changes:Pulsars, Pulsars:Magellanic Clouds, Pulsars:Period Changes, Pulsars:X Rays, X Rays:Pulsars %U https://ui.adsabs.harvard.edu/abs/1984ASNYN...2....7H %R 1984S&T....68..324C %T Book-Review - Superstars %A Clark, D. H.; Seward, F. D. %J Sky and Telescope %V 68 %D 01/1984 %P 324 %U https://ui.adsabs.harvard.edu/abs/1984S&T....68..324C %R 1983A&A...126..357D %T The X-ray emission of the old Nova V603 Aquilae (1918). %A Drechsel, H.; Rahe, J.; Wargau, W.; Seward, F. D.; Wang, Z. R. %F AA(University of Erlangen-Nuremberg, Astronomical Institute), AB(University of Erlangen-Nuremberg, Astronomical Institute), AC(University of Erlangen-Nuremberg, Astronomical Institute), AD(Harvard Smithsonian Center for Astrophysics) %J Astronomy and Astrophysics %V 126 %D 10/1983 %P 357 %L 362 %K Astronomical Spectroscopy, Emission Spectra, Light Curve, Novae, Spaceborne Astronomy, X Ray Sources, Astronomical Photometry, Stellar Mass Accretion, White Dwarf Stars, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1983A&A...126..357D %B X-ray observations of the old nova V603 Aql have been obtained with the IPC and MPC instruments aboard the Einstein Observatory during 1.7 consecutive orbital cycles. Periodic orbital phase-dependent flux variations are detected with large amplitude flickering superimposed on the sinusoidal X-ray light curve. The spectrum is hard, characterized by a temperature of 20 - 30 keV, and the maximum X-ray luminosity observed was ≡3×10³³ erg s^-1. The X-ray measurements are compared with recent optical photometric observations, and the origin of the periodic modulation of the optical and X-ray flux is discussed. %R 1983ApJ...273..688W %T The X-ray lobes of SS 433. %A Watson, M. G.; Willingale, R.; Grindlay, J. E.; Seward, F. D. %F AA(University of Leicester, UK), AB(University of Leicester, UK), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics) %J The Astrophysical Journal %V 273 %D 10/1983 %P 688 %L 696 %K Binary Stars, Stellar Spectrophotometry, Stellar Structure, X Ray Sources, Astronomical Maps, Emission Spectra, Heao 2, Line Spectra, Spectrum Analysis, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1983ApJ...273..688W %B The authors report observations of SS433 and the surrounding region made with the imaging detectors on the Einstein Observatory. The observations are used to map a ≡2°×1° region containing W50 centered on SS433. The results show two bright, diffuse lobes of X-ray emission symmetrically displaced E and W of SS433, aligned along the long axis of W50. The bulk of the emission from each lobe is confined to a region subtending an angle of ≡30° at the central object. The soft X-ray luminosity of each lobe is ≡6×10³⁴ erg s^-1, and X-ray spectra indicate that the diffuse emission is considerably softer than SS433 itself. The properties and origin of these lobes, and their relationship to W50, are discussed in the context of the kinematic beam model for SS433. %H IOP %Y DOI: 10.1086/161403 %R 1983JGR....88.7731M %T The detection of x rays from Jupiter %A Metzger, Albert E.; Luthey, Joe L.; Gilman, David A.; Hurley, Kevin C.; Schnopper, Herbert W.; Seward, Frederick D.; Sullivan, James D. %F AA(Jet Propulsion Laboratory), AB(Jet Propulsion Laboratory), AC(NASA HQ), AD(CNRS, Centre d'Études Spatiales des Rayonnements, Toulouse, France), AE(DTU Physics, Lyngby), AF(Harvard Smithsonian Center for Astrophysics), AG(Massachusetts Institute of Technology) %J Journal of Geophysical Research %V 88 %D 10/1983 %P 7731 %L 7741 %K Heao 2, Jupiter Atmosphere, Planetary Radiation, X Rays, Auroral Zones, Energy Spectra, Oxygen Ions, Planetary Magnetospheres, Polar Regions, Radiant Flux Density, Sulfur, JUPITER, X-RAYS, ENERGY, POLAR REGIONS, OBSERVATIONS, ASTRONOMY, FLUX, IMAGERY, DENSITY, LUMINOSITY, SPECTRA, CHARACTERISTICS, EMISSIONS, IPC, AURORAS, EINSTEIN X-RAY ASTRONOMY SATELLITE, IMAGING PROPORTIONAL COUNTER %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1983JGR....88.7731M %B X-rays in the energy band 0.2-3.0 keV have been detected coming from both polar regions of Jupiter. The observations were made in 1979 and 1981 by using the imaging proportional counter and high resolution imaging detectors on the Einstein X-ray astronomy satellite. The measured flux density of ~6 x 10^-⁴ cm^-²s^-¹ at earth corresponds to an X-ray luminosity of ~4×10⁹ W in the 0.2- to 3.0-keV energy band. The energy spectrum of the X-rays is extremely soft and can be characterized by a power law with an exponent of ~2.3. Detector energy resolution is insufficient to distinguish a soft line spectrum from a continuum. However, the shape of the response and the observed X-ray power indicate that the source of this auroral emission is not electron bremsstrahlung as on the earth, but is most probably line emission from O and S ions with energies between 0.03 and 4.0 MeV/nucleon precipitating from the outer boundary of the Io plasma torus at L~8. %Y DOI: 10.1029/JA088iA10p07731 %R 1983BAAS...15..953W %T An X-Ray Investigation of the Unusual Supernova Remnant CTB80 %A Wang, Z. R.; Seward, F. D. %J Bulletin of the American Astronomical Society %V 15 %D 09/1983 %P 953 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1983BAAS...15..953W %R 1983ApJ...267..711W %T The period history of the X-ray pulsar in MSH 15-52. %A Weisskopf, M. C.; Elsner, R. F.; Darbo, W.; Leahy, D.; Naranan, S.; Sutherland, P. G.; Grindlay, J. E.; Harnden, F. R., Jr.; Seward, F. D. %F AA(NASA Marshall Space Flight Center), AB(NASA Marshall Space Flight Center), AC(NASA Marshall Space Flight Center), AD(NASA Marshall Space Flight Center), AE(NASA Marshall Space Flight Center), AF(Harvard Smithsonian Center for Astrophysics), AG(Harvard Smithsonian Center for Astrophysics) %J The Astrophysical Journal %V 267 %D 04/1983 %P 711 %L 712 %K Periodic Variations, Pulsars, Pulse Duration, Supernova Remnants, X Ray Sources, Cross Correlation, Light Curve, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1983ApJ...267..711W %B New and refined mesurements of the pulse period of the X-ray pulsar in the supernova remnant MSH 15-52 are presented. The data were obtained with the Monitor proportional Counter on board the HEAO 2 observatory. The period measurements were obtained by analyzing pulse arrival times determined by cross-correlating sample pulse profiles with a master template. The period history for the source and a representative 0.15 s X-ray light curve are shown. The X-ray measurements alone lead to a refined value of the period derivative of (1.5382 + or -0.0024) x 10 to the -12th s/s, while including the results of more recent radio observations leads to a value of (1.54029 + or -0.00095) x 10 to the -12th s/s. These results indicate a hard-point source surrounded by diffuse nebular emission. %H IOP %Y DOI: 10.1086/160908 %R 1983ApJ...267..698S %T MSH 15-52 : a supernova remnant containing two compact X-ray sources. %A Seward, F. D.; Harnden, F. R., Jr.; Murdin, P.; Clark, D. H. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Royal Greenwich Observatory), AD(Rutherford Appleton Laboratory) %J The Astrophysical Journal %V 267 %D 04/1983 %P 698 %L 710 %K Nebulae, Pulsars, Radio Sources (Astronomy), Supernova Remnants, X Ray Sources, Emission Spectra, H Alpha Line, Heao 2, Infrared Spectra, Interstellar Gas, Shock Wave Interaction, Stellar Evolution, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1983ApJ...267..698S %B Einstein observations show two small-diameter, bright X-ray sources within the shell of the Galactic radio supernova remnant (SNR) MSH 15-52. X-ray spectra and optical extinction indicate that both compact sources are at least as distant, 4.2 kpc, as the diffuse emission from the shell. The source closest to the middle of the remnant shows strong regular X-ray pulsations with a period of 0.150 s. The second source is associated with an optical knot within the Hα nebula RCW 89 close to the northwestern rim of the SNR. UK Schmidt telescope photographs of RCW 89 support the hypothesis that the Hα nebula is part of the whole SNR. The authors discuss various possibilities of incorporating the apparently young pulsar (characteristic age ≡1600 years), the apparently old SNR (>10,000 yr), and the bright knot into a single consistent system. %H IOP %Y DOI: 10.1086/160907 %R 1983BAAS...15..637W %T X-Rays from the SNR 3C391 %A Wang, Z. R.; Seward, F. D. %J Bulletin of the American Astronomical Society %V 15 %D 03/1983 %P 637 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1983BAAS...15..637W %R 1983BAAS...15..636V %T Einstein OGS/MPC Observations of Cygnus X-2 %A Vrtilek, S. Dil; Kahn, S. M.; Seward, F. D.; Grindlay, J. E. %J Bulletin of the American Astronomical Society %V 15 %D 03/1983 %P 636 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1983BAAS...15..636V %R 1983ApJ...266..287S %T The mass of Tycho's supernova remnant as determined from a high-resolution X-ray map. %A Seward, F.; Gorenstein, P.; Tucker, W. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics) %J The Astrophysical Journal %V 266 %D 03/1983 %P 287 %L 297 %K Astronomical Maps, Interstellar Matter, Nebulae, Stellar Mass, Supernova Remnants, X Ray Sources, Astronomical Models, Ejecta, Heao 2, High Resolution, Mass Distribution, Shock Waves, X Ray Imagery, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1983ApJ...266..287S %B High resolution Einstein Observatory X ray images of Tycho's supernova remnant (SNR) are discussed. The object has features of a shock heated shell in the interstellar medium, accompanied by an inner shell with clumped ejecta. The measurements were made for 22 hr on Feb. 8, 1979, revealing a circular SNR, a thin emission shelf at the outer edge of the remnant, no emission in the central object, and most emissions concentrated in small, clumpy objects within a spherical shell. Three components of the X ray emission were identified, and calculations of the swept-up mass, the diffuse component of the ejecta shell, and the clumpy ejecta are reported to be 2.2, 1.2, and 0.7 solar mass, respectively. The SNR is concluded to be at an evolutionary stage between uniform expansion and adiabatic changes. %H IOP %Y DOI: 10.1086/160778 %R 1983S&T....65..223R %T TYCHO Kepler and Einstein / Supernova Remnants %A Reid, P.; Seward, F.; White, R. L.; Long, K. S.; Dennefeld, M.; Leibowitz, E. M.; Danziger, I. J. %J Sky and Telescope %V 65 %D 03/1983 %P 223 %U https://ui.adsabs.harvard.edu/abs/1983S&T....65..223R %R 1983IAUS..101..289P %T High resolution X-ray images of Puppis A and IC 443 %A Petre, R.; Winkler, P. F.; Seward, F. D.; Willingale, R.; Rolf, D.; Woods, N.; Canizares, C. R. %F AA(Goddard Space Flight Center, Astrophysics Division), AB(Middlebury College, Vermont), AC(Harvard Smithsonian Center for Astrophysics), AD(University of Leicester, UK), AE(University of Leicester, UK), AF(University of Leicester, UK) %J Supernova Remnants and their X-ray Emission %V 101 %D 01/1983 %P 289 %L 293 %K Astronomical Spectroscopy, High Resolution, Spatial Distribution, Supernova Remnants, X Ray Astronomy, Brightness Distribution, Brightness Temperature, Interstellar Matter, Molecular Clouds, Spectral Resolution, X Ray Imagery, Astronomy %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I TOC: Table of Contents; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1983IAUS..101..289P %B The authors present soft X-ray photomosaic images of two supernova remnants, Puppis A and IC443, constructed from a series of exposures by the Einstein imaging instruments. The complex morphologies displayed in these images reflect the interaction between "middle-aged" supernova remnants and various components of the interstellar medium. Surface brightness variations across Puppis A suggest that inhomogeneities on scales from 0.2 to 30 pc are present in the interstellar medium, while the structure of IC443 is apparently dominated by the interaction between the remnant and a giant molecular cloud. %R 1983IAUS..101..459G %T X-ray studies of SS433 %A Grindlay, J. E.; Band, D.; Seward, F.; Stella, L.; Watson, M. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics), AE(University of Leicester, UK) %J Supernova Remnants and their X-ray Emission %V 101 %D 01/1983 %P 459 %L 463 %K Eclipsing Binary Stars, Stellar Models, X Ray Astronomy, X Ray Sources, Astronomical Maps, B Stars, Black Holes (Astronomy), Heao 2, Kinetic Energy, Plasma Jets, Relativistic Plasmas, Stellar Mass Accretion, Synchrotron Radiation, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I TOC: Table of Contents; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1983IAUS..101..459G %B Results of Einstein Observations of SS433 are discussed which address both the nature of the diffuse X-ray lobes and the relationships between SS433 and W50, as well as the time variability and nature of the central X-ray source. The diffuse X-ray lobes extend out to the quasi-spherical shell seen in the radio maps of W50 and suggest that the X-ray lobes are powered by the interaction of shock-heating from the SS433 jets and the denser material in the W50 shell. The central X-ray source in SS433 is time variable but only on timescales of less than 500-1000 sec. Flares, in which the non-thermal spectrum hardens, are detected at two preferred phases in the 13.08 day binary orbit. Constraints on the central X-ray source size as well as a possible eclipse by the companion star suggest the compact object in SS433 may be a black hole (approx 10 solar mass). %R 1983Mercu..12...56S %T Discovery of a New Pulsar Within a Supernova Remnant %A Seward, F. D.; Harnden, F. R., Jr. %J Mercury %V 12 %D 01/1983 %P 56 %U https://ui.adsabs.harvard.edu/abs/1983Mercu..12...56S %R 1983IAUS..101....1G %T The mass and structure of the remnant of Tycho's supernova %A Gorenstein, P.; Seward, F.; Tucker, W. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics) %J Supernova Remnants and their X-ray Emission %V 101 %D 01/1983 %P 1 %L 15 %K Ejecta, Interstellar Matter, Mass Distribution, Supernova Remnants, X Ray Sources, Astronomical Maps, High Resolution, Neutron Stars, Radii, Shock Heating, Stellar Mass Ejection, Surface Temperature, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I TOC: Table of Contents; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1983IAUS..101....1G %B A high-resolution X-ray image of Tycho's supernova remnant obtained from the Einstein Observatory reveals three components of X-ray emission, which are identified with shocked interstellar material, diffuse ejecta, and clumpy ejecta. This picture is applied to derive the mass of X-ray-emitting material. Assuming a distance of 3 kpc, an absorbing column density of 3 x 10 to the 21st atoms/sq cm, and using an ion-electron nonequilibrium calculation for the emissivity, the average density of the ISM is found to be 0.4 atoms/cu cm, and the energy contained in the remnant is 1.4 x 10 to the 51st ergs. The total mass of X-ray-emitting material in the remnant is about 4 solar mass, about 2 solar mass ejecta and about 2 solar mass swept up, putting the remnant at an intermediate state between a free expansion and the Sedov phase. There is no evidence for neutron star. The upper limit on the surface temperature is in the range 1.1 to 1.8 million K. %R 1983IAUS..101..417S %T Supernova remnants with compact X-ray sources %A Seward, F. D.; Harnden, F. R., Jr.; Murdin, P. G.; Wood, R.; Gilmozzi, R.; Clark, D. H.; Danziger, I. J.; Furr, A. W. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Royal Greenwich Observatory), AD(Royal Greenwich Observatory), AE(Royal Greenwich Observatory), AF(Rutherford Appleton Laboratory), AG(European Southern Observatory, Germany), AH(University of Sussex, UK) %J Supernova Remnants and their X-ray Emission %V 101 %D 01/1983 %P 417 %L 419 %K Astronomical Spectroscopy, Crab Nebula, Pulsars, Supernova Remnants, X Ray Sources, Infrared Spectra, Radial Velocity, Astrophysics %I ABSTRACT: Abstract; %I TOC: Table of Contents; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1983IAUS..101..417S %B Observational data indicate that the supernova remnants (SNR) MSH 15 - 52 and RCW 89 and the optical knot within RCW 89 are part of a single system.Two compact X-ray sources, thought to be 4.2 kpc from earth, have been detected inside MSH 15 - 52. The knot displays forbidden Fe II lines as intense as Balmer lines. Filaments extend from RCW 89 to MSH 15 - 52. It is suggested that the supernova ejecta interact with the interstellar medium to produce the observed X-ray, optical, and radio features, implying that the two SNR are closer in age than previously thought. A pulsar may power the knot and RCW 89. Radial velocity observations of the Crab Nebula are also reported. The thick shell contains bright inner and dim outer components surrounded by a higher velocity halo. Synchrotron emissions arise from within the shell and are accompanied by a sharp brightness discontinuity at the bright inner shell. %R 1983IAUS..101..281H %T The X-ray structure of the supernova remnant G78.2 + 2.1 %A Higgs, L. A.; Landecker, T. L.; Seward, F. D. %F AA(Dominion Radio Astrophysical Observatory), AB(Dominion Radio Astrophysical Observatory), AC(Harvard Smithsonian Center for Astrophysics) %J Supernova Remnants and their X-ray Emission %V 101 %D 01/1983 %P 281 %L 286 %K Supernova Remnants, X Ray Sources, Luminosity, Nebulae, Radio Emission, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I TOC: Table of Contents; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1983IAUS..101..281H %B The south-eastern portion of the supernova remnant G78.2+2.1, in Cygnus, has been detected as a weak X-ray source by the Einstein Observatory. The X-ray structure is similar to that of the radio filaments in this region, and confirms that X-ray emission in this portion of the "Cygnus super-bubble" does originate in a known supernova remnant. Marginally significant variations in X-ray hardness across the mapped area have been detected and can be related to known radio and optical features of the remnant. In its X-ray properties, G78.2+2.1 resembles IC443. %R 1983IAUS..101..273W %T Einstein observations of the SNRs IC443, W44 and W49B %A Watson, M. G.; Willingale, R.; Pye, J. P.; Rolf, D. P.; Wood, N.; Thomas, N.; Seward, F. D. %F AA(University of Leicester, UK), AB(University of Leicester, UK), AC(University of Leicester, UK), AD(University of Leicester, UK), AE(University of Leicester, UK), AF(University of Leicester, UK), AG(Harvard Smithsonian Center for Astrophysics) %J Supernova Remnants and their X-ray Emission %V 101 %D 01/1983 %P 273 %L 280 %K Molecular Clouds, Molecular Spectra, Supernova Remnants, X Ray Astronomy, X Ray Imagery, Abundance, Electron Density (Concentration), Heao 2, Limb Brightening, Stellar Luminosity, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I TOC: Table of Contents; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1983IAUS..101..273W %B The authors present soft X-ray observations made with the Einstein Observatory Imaging Proportional Counter (IPC) of IC443, W44 and W49B. The X-ray emission from IC443 and W44 is clearly concentrated within the interior of the remnant with little or no evidence for a limb-brightened shell. Significant spectral differences are found across the X-ray images in both remnants which are interpreted as being due to a combination of differential absorption by molecular clouds and intrinsic spatial temperature variations. The distant remnant W49B is only just resolved in the IPC observations, but additional observations with the High Resolution Imager indicate a similar "infilled" morphology to IC443 and W44. %R 1983IAUS..101...59S %T An X-ray halo around Cassiopeia A %A Stewart, G. C.; Fabian, A. C.; Seward, F. D. %F AA(University of Cambridge, UK), AB(University of Cambridge, UK), AC(Harvard Smithsonian Center for Astrophysics) %J Supernova Remnants and their X-ray Emission %V 101 %D 01/1983 %P 59 %L 64 %K Astronomical Spectroscopy, Cassiopeia A, Emission Spectra, Supernova Remnants, X Ray Sources, Brightness Distribution, H Ii Regions, Halos, Spectral Energy Distribution, Visible Spectrum, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I TOC: Table of Contents; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1983IAUS..101...59S %B The large-scale X-ray emission of Cas A is characterized, and mechanisms are proposed to explain it. The Einstein HRI image of Murray et al. (1979) is binned into 16-arcsec pixels, a point-spread function based on the 2.04-keV monochromatic Zr source is applied, and the data are modeled as a series of circularly symmetric rings of emission. A significant excess extending to a radius of 6 arcmin (roughly the size of the optical H II region) is found to have a total 0.5-3-keV luminosity of about 5 x 10 to the 34th erg/s, or about 2 percent of the total luminosity of Cas A, which is assumed to lie at a distance of 3 kpc. Thermal bremsstrahlung, synchrotron radiation, and dust scattering of the main-shell emission are examined and found to be plausible emission mechanisms; further observations are required to identify the one active in Cas A. %R 1983MitAG..60..357D %T Röntgen-Messungen von V 603 Aquilae %A Drechsel, H.; Rahe, J.; Wargau, W.; Seward, F.; Wang, Z. %J Mitteilungen der Astronomischen Gesellschaft Hamburg %V 60 %D 01/1983 %P 357 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1983MitAG..60..357D %R 1983IAUS..101..405S %T Supernova remnants with central pulsars %A Seward, F. D. %F AA(Harvard Smithsonian Center for Astrophysics; University of Cambridge, UK) %J Supernova Remnants and their X-ray Emission %V 101 %D 01/1983 %P 405 %L 416 %K Pulsars, Supernova Remnants, X Ray Sources, Astronomical Models, Crab Nebula, Synchrotron Radiation, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I TOC: Table of Contents; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1983IAUS..101..405S %B The recent discovery of a central pulsing X-ray source makes MSH 15 - 52 the third SNR to contain a radio pulsar surrounded by diffuse X-ray emission. The pulsar periods are all increasing with time and the consequent loss of rotational kinetic energy is enough, in each remnant, to power a synchrotron nebula with the observed luminosity and volume. After a review of the properties of the Crab Nebula it will be shown that both Vela X and MSH 15 - 52 have the same relationship between the central pulsar and diffuse emission. Using empirical rules derived from these SNR, it is demonstrated that other plerionic remnants have similar characteristics. Two accretion-powered central sources can be distinguished from radio pulsars in SNR by the relatively high X-ray luminosity of the central source compared to that of possible synchrotron diffuse emission. %R 1982ASIC...90..519S %T Einstein observations of supernova remnants %A Seward, F. D. %F AA(Harvard Smithsonian Center for Astrophysics) %J Supernovae: A Survey of Current Research %V 90 %D 11/1982 %P 519 %L 528 %K Galactic Radiation, Heao 2, Stellar Evolution, Supernova Remnants, X Ray Imagery, X Ray Sources, Astronomical Maps, Crab Nebula, Diffuse Radiation, Ejecta, Interstellar Matter, Astronomy %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I TOC: Table of Contents; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1982ASIC...90..519S %B X-ray maps of nine supernova remnants ordered approximately by age and by prominence of central objects are presented. The maps were prepared from data collected by investigators at the Einstein Observatory of the soft X-ray emission from approximately 40 galactic supernova remnants. The detectors covered the energy range of 0.2-4.0 keV and the data were collected between November 1978-April 1981. It is found that the young supernovae appear as strongly limb brightened shells and both ejecta from the exploded star and hot material behind the shock propagating in the interstellar medium are observed. The mass of material in the different components can be calculated and the dynamic state of the supernova remnants can be determined. In addition, compact objects are found in some remnants as point sources with X-ray pulsed fractions ranging from 0 to approximately 100%. Diffuse X-rays powered by high energy particles associated with the compact sources are also detected. %Y DOI: 10.1007/978-94-009-7876-8_32 %R 1982JRASC..76R.322L %T X-ray structure of the SNR G78.2+2.1. %A Landecker, T. L.; Higgs, L. A.; Roger, R. S.; Seward, F. D. %J Journal of the Royal Astronomical Society of Canada %V 76 %D 10/1982 %P 322 %K Supernova Remnants:X Rays %U https://ui.adsabs.harvard.edu/abs/1982JRASC..76R.322L %R 1982BAAS...14R.944K %T High Resolution Soft X-Ray Spectra of Scorpius X-1: The Structure of Circumsource Accreting Material %A Kahn, S. M.; Seward, F. D.; Chebowski, T. %J Bulletin of the American Astronomical Society %V 14 %D 09/1982 %P 944 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1982BAAS...14R.944K %R 1982BAAS...14Q.966H %T Further Einstein Results for the New Circinus Pulsar (PSR 1509-58) %A Harnden, F. R., Jr.; Seward, F. D. %J Bulletin of the American Astronomical Society %V 14 %D 09/1982 %P 966 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1982BAAS...14Q.966H %R 1982ApJ...260..233M %T X-ray spectrum of Capella and its relation to coronal structure and ultraviolet emission. %A Mewe, R.; Gronenschild, E. H. B. M.; Westergaard, N. J.; Heise, J.; Seward, F. D.; Chlebowski, T.; Kuin, N. P. M.; Brinkman, A. C.; Dijkstra, J. H.; Schnopper, H. W. %F AA(Netherlands Institute for Space Research), AB(Netherlands Institute for Space Research), AC(Netherlands Institute for Space Research), AD(Netherlands Institute for Space Research), AE(Netherlands Institute for Space Research), AF(DTU Physics, Lyngby), AG(DTU Physics, Lyngby), AH(Harvard Smithsonian Center for Astrophysics), AI(Nicolaus Copernicus Astronomical Center, Warsaw), AJ(University of Utrecht, Department of Physics and Astronomy) %J The Astrophysical Journal %V 260 %D 09/1982 %P 233 %L 239 %K Binary Stars, Stellar Coronas, X Ray Astronomy, X Ray Spectra, Abundance, Coronal Loops, Heao 2, Ultraviolet Radiation, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1982ApJ...260..233M %B The binary system Capella has been observed on 1979 March 15 and on 1980 March 15-17, with the objective grating spectrometer on board the Einstein Observatory. The spectrum measured with the 1000 1/mm grating covers the range 5-30 A with a resolution less than 1 A. The spectra show evidence for a bimodal temperature distribution of emission measure in an optically thin plasma with one component about 5,000,000 K and the other one about 10,000,000 K. Spectral features can be identified with line emissions from O VIII, Fe XVII, Fe XVIII, Fe XXIV, and Ne X ions. Good spectral fits have been obtained assuming standard cosmic abundances. The data are interpreted in terms of emission from hot static coronal loops rather similar to the magnetic arch structures found on the sun. It is shown that the conditions for such a model can exist on Capella. Typical values of loop base pressure and half-length are derived for both temperature components and discussed in relation to UV observations. %H IOP %Y DOI: 10.1086/160249 %R 1982ApOpt..21.2012S %T Calibration and efficiency of the Einstein objective grating spectrometer %A Seward, F. D.; Chlebowski, T.; Delvaille, J. P.; Henry, J. P.; Kahn, S. M.; van Speybroeck, L.; Dijkstra, J. H.; Brinkman, A. C.; Heise, J.; Mewe, R.; Schrijver, J. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics), AE(Harvard Smithsonian Center for Astrophysics), AF(Harvard Smithsonian Center for Astrophysics), AG(Netherlands Institute for Space Research), AH(Netherlands Institute for Space Research), AI(Netherlands Institute for Space Research), AJ(Netherlands Institute for Space Research) %J Applied Optics %V 21 %D 06/1982 %P 2012 %L 2021 %K Astronomical Spectroscopy, Calibrating, Gratings (Spectra), Heao 2, Image Resolution, Spaceborne Telescopes, X Ray Astronomy, Optical Paths, Prelaunch Problems, Run Time (Computers), Spaceborne Astronomy, Spectral Resolution, Spacecraft Instrumentation, GRATINGS, X RAYS, SPACE OPTICS %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %I PUB_PDF: Publisher PDF; %U https://ui.adsabs.harvard.edu/abs/1982ApOpt..21.2012S %B The Einstein Observatory, a large satellite dedicated to X-ray astronomy, carried the first large X-ray telescope to be placed in orbit and an objective grating spectrometer with two sets of gratings. This paper lists prelaunch calibration results and describes the derivation of spectrometer efficiency and resolution. Several calibration spectra are shown, and theoretical grating parameters are derived from the calibration results. %Y DOI: 10.1364/AO.21.002012 %R 1982ApJ...256..530S %T X-ray emission from the Carina Nebula and the associated early stars. %A Seward, F. D.; Chlebowski, T. %F AA(Harvard Smithsonian Center for Astrophysics) %J The Astrophysical Journal %V 256 %D 05/1982 %P 530 %L 542 %K Diffuse Radiation, Early Stars, Hydrogen Clouds, Nebulae, O Stars, Wolf-Rayet Stars, X Ray Sources, Astronomical Maps, Astronomical Photography, Heao 2, Interstellar Gas, Proportional Counters, Star Clusters, Stellar Luminosity, Stellar Winds, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1982ApJ...256..530S %B New Einstein observations of the Carina Nebula show the extent of the diffuse X-ray nebula to be 1.1 deg E-W by 0.7 deg N-S. The diffuse X-ray emission is generally associated with optically bright regions, but the correlation is not exact. Emission is strongest from regions bordering the apparently overlying dust lane, indicating an interaction between the energetic material of the optical nebula and the region containing the dust. The diffuse X-rays are from hot gas with temperatures of about 10 million K, and electron densities of 0.1-1/cu cm. The energy to heat this gas probably comes from strong stellar winds of the early stars embedded in the nebula. X-rays from 15 O and W-R stars in the Carina OBI association have been detected. Data are consistent with the hypothesis that X-ray luminosity is equal to about 2.0 x 10 to the -7th of bolometric luminosity for all O stars in this region with remarkably little scatter. X-ray emission from the three W-R stars observed is significantly different. In particular, the WN6 star, HD 93162, has an X-ray luminosity equal to about 2.0 x 10 to the -6th of bolometer luminosity, a factor of 30 higher than for two other W-R stars in this nebula, and perhaps the highest X-ray luminosity/bolometric luminosity of any W-R star for which X-ray observations have been made. %H IOP %Y DOI: 10.1086/159929 %R 1982ApJ...256L..45S %T A new, fast X-ray pulsar in the supernova remnant MSH 15-52. %A Seward, F. D.; Harnden, F. R., Jr. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics) %J The Astrophysical Journal %V 256 %D 05/1982 %P L45 %L L47 %K Pulsars, Supernova Remnants, X Ray Sources, Nebulae, Periodic Variations, Astronomy %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1982ApJ...256L..45S %B A pulsing X-ray source has been discovered within the shell of the supernova remnant MSH 15-52. The period is 0.150 s, and the rate of increase of period with time is the highest measured for any pulsar. These characteristics and the fact that the pulsar is surrounded by a small, bright nebula indicate that this object is very similar to the Crab pulsar. %H IOP %Y DOI: 10.1086/183793 %R 1982ApJ...252..239K %T Coordinated X-ray, optical and radio observations of flaring activityon YZ Canis Minoris. %A Kahler, S.; Golub, L.; Harnden, F. R.; Liller, W.; Seward, F.; Vaiana, G.; Lovell, B.; Davis, R. J.; Spencer, R. E.; Whitehouse, D. R.; Feldman, P. A.; Viner, M. R.; Leslie, B.; Kahn, S. M.; Mason, K. O.; Davis, M. M.; Crannell, C. J.; Hobbs, R. W.; Schneeberger, T. J.; Worden, S. P.; Schommer, R. A.; Vogt, S. S.; Pettersen, B. R.; Coleman, G. D.; Karpen, J. T.; Giampapa, M. S.; Hege, E. K.; Pazzani, V.; Rodono, M.; Romeo, G.; Chugainov, P. F. %F AA(American Science and Engineering, Cambridge, Massachusetts), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics), AE(Harvard Smithsonian Center for Astrophysics), AF(Harvard Smithsonian Center for Astrophysics; Astronomical Observatory of Palermo), AG(Jodrell Bank Centre for Astrophysics), AH(Jodrell Bank Centre for Astrophysics), AI(Jodrell Bank Centre for Astrophysics), AJ(Goddard Space Flight Center, Astrophysics Division) %J The Astrophysical Journal %V 252 %D 01/1982 %P 239 %L 249 %K Dwarf Stars, Flare Stars, Late Stars, Radio Spectra, Stellar Flares, Stellar Spectrophotometry, X Ray Sources, Emission Spectra, Light (Visible Radiation), M Stars, Periodic Variations, Radiant Flux Density, Stellar Spectra, Stellar Temperature, Ultraviolet Spectra, Astronomy %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1982ApJ...252..239K %B The YZ Canis Minoris (Gliese 285), a late-type dwarf star with Balmer emission (dM4.5e), is a member of the UV Ceti class of flare stars. Obtaining good X-ray observations of a dMe star flare is important not only for understanding the physics of flares but also for testing current ideas regarding the similarity between stellar and solar flares. The Einstein X-ray Observatory has made it possible to conduct X-ray observations of dMe stars with unprecedented sensitivity. A description is presented of the results of a program of ground-based optical and radio observations of YZ CMi coordinated with those of the Einstein Observatory. The observations were carried out as part of a coordinated program on October 25, 26, and 27, 1979, when YZ CMi was on the dawn side of the earth. Comprehensive observational data were obtained of an event detected in all three wavelength regions on October 25, 1979. %H IOP %Y DOI: 10.1086/159551 %R 1982AdSpR...2i.153S %T Einstein observations of supernova remnants %A Seward, F. D. %F AA(Harvard Smithsonian Center for Astrophysics) %J Advances in Space Research %V 2 %D 01/1982 %P 153 %L 161 %K Heao 2, Stellar Spectra, Supernova Remnants, X Ray Astronomy, Interstellar Matter, Pulsars, Spatial Distribution, Spectral Resolution, Stellar Envelopes, Stellar Evolution, Stellar Mass Ejection, Stellar Temperature, X Ray Spectra, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1982AdSpR...2i.153S %B Recent observations of SNRs have produced X-ray images with resolution comparable to that routinely achieved at optical wavelengths. There has also been a great improvement in the quality of X-ray spectra. Since most of the energy radiated by SNRs appears as X-rays, these new data are crucial to studies of SNRs, the interaction of SNRs with the interstellar medium, and the SN explosion itself. Images show a variety of shapes ranging from shel-like remnants to those dominated by the influence of central objects which appear both as point sources and as centers of diffuse activity. Once the temperature and spatial distribution of X-ray emitting material is known, the mass of ejected material and the energy release of the SN explosion can sometimes be calculated. X-ray images and spectra of several remnants are shown, and some quantitative results are given. %Y DOI: 10.1016/0273-1177(82)90266-6 %R 1981ApJ...245..163V %T Results from an extensive Einstein stellar survey. %A Vaiana, G. S.; Cassinelli, J. P.; Fabbiano, G.; Giacconi, R.; Golub, L.; Gorenstein, P.; Haisch, B. M.; Harnden, F. R., Jr.; Johnson, H. M.; Linsky, J. L.; Maxson, C. W.; Mewe, R.; Rosner, R.; Seward, F.; Topka, K.; Zwaan, C. %F AA(Harvard Smithsonian Center for Astrophysics; Astronomical Observatory of Palermo), AB(University of Wisconsin, Madison, Washburn Observatory), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics), AE(Harvard Smithsonian Center for Astrophysics), AF(Harvard Smithsonian Center for Astrophysics), AG(Joint Institute for Laboratory Astrophysics, Boulder), AH(Harvard Smithsonian Center for Astrophysics), AI(Lockheed Martin, Palo Alto), AJ(Joint Institute for Laboratory Astrophysics, Boulder; National Institute of Standards and Technology, Maryland), AK(Harvard Smithsonian Center for Astrophysics), AL(University of Utrecht, Department of Physics and Astronomy), AM(Harvard Smithsonian Center for Astrophysics), AN(Harvard Smithsonian Center for Astrophysics), AO(Harvard Smithsonian Center for Astrophysics), AP(University of Utrecht, Department of Physics and Astronomy) %J The Astrophysical Journal %V 245 %D 04/1981 %P 163 %L 182 %K Early Stars, Hertzsprung-Russell Diagram, Main Sequence Stars, Stellar Coronas, X Ray Sources, B Stars, Emission Spectra, O Stars, Stellar Gravitation, Stellar Luminosity, Stellar Temperature, White Dwarf Stars, Astronomy %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1981ApJ...245..163V %B The preliminary results of the Einstein Observatory stellar X-ray survey are presented. To date, 143 soft X-ray sources have been identified with stellar counterparts, leaving no doubt that stars in general constitute a pervasive class of low-luminosity galactic X-ray sources. Stars along the entire main sequence, of all luminosity classes, pre-main sequence stars as well as very evolved stars have been detected. Early type OB stars have X-ray luminosities in the range 10 to the 31st to 10 to the 34th ergs/s; late type stars show a somewhat lower range of X-ray emission levels, from 10 to the 26th to 10 to the 31st ergs/s. Late type main-sequence stars show little dependence of X-ray emission levels upon stellar effective temperature; similarly, the observations suggest weak, if any, dependence of X-ray luminosity upon effective gravity. Instead, the data show a broad range of emission levels (about three orders of magnitude) throughout the main sequence later than F0. %H IOP %Y DOI: 10.1086/158797 %R 1981BAAS...13..512C %T New Einstein Observations of the Eta Carinae Nebula %A Chlebowski, T.; Seward, F. D. %J Bulletin of the American Astronomical Society %V 13 %D 03/1981 %P 512 %I CITATIONS: Citations to the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1981BAAS...13..512C %R 1981BAAS...13..865G %T Search for Extended X-ray Emission Surrounding the Crab Nebula %A Gorenstein, P.; Harnden, F. R., Jr.; Mitchell, M.; Seward, F. D. %J Bulletin of the American Astronomical Society %V 13 %D 03/1981 %P 865 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1981BAAS...13..865G %R 1981BAAS...13..865K %T The EINSTEIN Objective Grating X-ray Spectrum of the Crab Nebula %A Kahn, S. M.; Seward, F. D.; Chlebowski, T.; Dijkstra, J. %J Bulletin of the American Astronomical Society %V 13 %D 03/1981 %P 865 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1981BAAS...13..865K %R 1981BAAS...13R.795S %T MSH 15-5(2) - A SNR Containing 2 Compact X-ray Sources %A Seward, F.; Murdin, P. %J Bulletin of the American Astronomical Society %V 13 %D 03/1981 %P 795 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1981BAAS...13R.795S %R 1981SSRv...30..185G %T X-Ray Spectroscopic Investigation of the Coronal Structure of Capella %A Gronenschild, E. H. B. M.; Mewe, R.; Westergaard, N. J.; Heise, J.; Seward, F. D.; Chlebowski, T.; Kuin, N. P. M.; Brinkman, A. C.; Dijkstra, J. H.; Schnopper, H. W. %F AA(University of Utrecht, Department of Physics and Astronomy), AB(University of Utrecht, Department of Physics and Astronomy), AC(University of Utrecht, Department of Physics and Astronomy), AD(University of Utrecht, Department of Physics and Astronomy), AE(University of Utrecht, Department of Physics and Astronomy), AF(DTU Physics, Lyngby), AG(DTU Physics, Lyngby), AH(Harvard Smithsonian Center for Astrophysics), AI(Harvard Smithsonian Center for Astrophysics), AJ(University of Utrecht, Department of Physics and Astronomy) %J Space Science Reviews %V 30 %D 03/1981 %P 185 %L 189 %K Binary Stars, Stellar Spectrophotometry, Stellar Structure, X Ray Sources, X Ray Spectroscopy, Abundance, Emission Spectra, Gratings (Spectra), Iron, Line Spectra, Neon, Spectral Resolution, Stellar Temperature, Temperature Distribution, Thermal Plasmas, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I TOC: Table of Contents; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1981SSRv...30..185G %B The binary system Capella (G6 III + F9 III) has been observed on 1979 March 15 and on 1980 March 15 17 with the Objective Grating Spectrometer (OGS) onboard the Einstein Observatory. The spectrum measured with the 1000 l/mm grating covers the range 5 30 Å with a resolution < 1 Å. The spectra show evidence for a bimodal temperature distribution of emission measure in an optically thin plasma with one component ∼ 5 million degrees and the other one ∼10 million degrees. Spectral features can be identified with line emissions from O VIII, Fe XVII, Fe XVIII, Fe XXIV, and Ne X ions. Good spectral fits have been obtained assuming standard cosmic abundances. The data are interpreted in terms of emission from hot static coronal loops rather similar to the magnetic arch structures found on the Sun. It is shown that the conditions required by this model exist on Capella. Mean values of loop parameters are derived for both temperature components. %Y DOI: 10.1007/BF01246017 %R 1981BAAS...13..834W %T The X-ray Lobes of SS433 %A Watson, M. G.; Grindlay, J. E.; Seward, F. D. %J Bulletin of the American Astronomical Society %V 13 %D 03/1981 %P 834 %I CITATIONS: Citations to the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1981BAAS...13..834W %R 1981BAAS...13..834G %T X-ray Variability of SS433 %A Grindlay, J.; Band, D.; Seward, F.; Leahy, D.; Weisskopf, M. %J Bulletin of the American Astronomical Society %V 13 %D 03/1981 %P 834 %I CITATIONS: Citations to the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1981BAAS...13..834G %R 1981MNRAS.194..569P %T An X-ray map of SN 1006 from the Einstein Observatory. %A Pye, J. P.; Punds, K. A.; Rolf, D. P.; Seward, F. D.; Smith, A.; Willingale, R. %F AA(University of Leicester, UK), AB(University of Leicester, UK), AC(University of Leicester, UK), AD(University of Leicester, UK), AE(University of Leicester, UK), AF(Harvard Smithsonian Center for Astrophysics) %J Monthly Notices of the Royal Astronomical Society %V 194 %D 02/1981 %P 569 %L 582 %K Astronomical Maps, Supernova Remnants, X Ray Imagery, X Ray Sources, X Ray Spectra, Astronomical Observatories, Brightness, Emission Spectra, Image Resolution, Proportional Counters, Space Plasmas, Three Dimensional Models, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1981MNRAS.194..569P %B An X-ray map of the SN 1006 supernova remnant acquired by the imaging proportional counter of the Einstein Observatory in the energy range 0.1-4 keV is presented. The image obtained from the imaging proportional counter shows a limb-brightened nebula, almost circular in outline with enhanced emission in two quadrants. The hardness ratio map reveals a large range of temperatures over the object, with the highest values near the limbs of the enhanced emission regions. Consideration of a three-dimensional model of the object indicates the presence of a shell of electron temperature varying between 10 to the 6th and 10 to the 7th K and density varying between 0.3 and 6/cu cm surrounding a fairly uniform interior, of electron temperature 1.5 x 10 to the 6th K and density 1.0/cu cm. The optical filaments are observed to lie parallel with the faintest edge of the X-ray shell, about 1 arcmin from the peak of X-ray emission. Mass visible in the X-ray image of 5-15 solar masses suggests that the supernova may have been of type II. No evidence is obtained for a hot stellar remnant. %H OUP %Y DOI: 10.1093/mnras/194.3.569 %R 1981ApJ...243..736S %T X-ray survey of the Small Magellanic Cloud. %A Seward, F. D.; Mitchell, M. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics) %J The Astrophysical Journal %V 243 %D 02/1981 %P 736 %L 743 %K Galactic Radiation, Magellanic Clouds, Stellar Radiation, X Ray Sources, Luminous Intensity, Proportional Counters, Stellar Coronas, Supernova Remnants, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %U https://ui.adsabs.harvard.edu/abs/1981ApJ...243..736S %B A region of over 40 square degrees centered on the Small Magellanic Cloud (SMC) has been surveyed with the imaging instruments of the Einstein Observatory. The survey is approximately complete to a luminosity of 10 to the 36th ergs/sec, and the faintest source detected, if in the SMC, has a luminosity of approximately 3 x 10 to the 35th ergs/sec. Twenty-six sources were clearly seen. Five are identified with objects not associated with the SMC. The only previously known source detected was SMC X-1 which, when in a high state, is the brightest source in the SMC. The second brightest source observed, a previously unknown supernova remnant (SNR), is located in the central part of the SMC. Four other weaker sources are probably also SNRs in the SMC. The remaining 15 sources are not yet identified and, since some are far from the center of the cloud, are probably not all members of the SMC. %H IOP %Y DOI: 10.1086/158641 %R 1981tesc.book..195G %T The Einstein Observatory and future X-ray telescopes. %A Giacconi, R.; Gorenstein, P.; Murray, S. S.; Schreier, E.; Seward, F.; Tananbaum, H.; Tucker, W. H.; van Speybroeck, L. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics), AE(Harvard Smithsonian Center for Astrophysics), AF(Harvard Smithsonian Center for Astrophysics), AG(Harvard Smithsonian Center for Astrophysics), AH(Harvard Smithsonian Center for Astrophysics) %J Telescopes for the 1980s, Annual Reviews Monograph %D 01/1981 %P 195 %L 278 %K Astronomical Observatories, Heao, Spaceborne Telescopes, X Ray Astronomy, X Ray Telescopes, Focal Plane Devices, Grazing Incidence, Grazing Incidence Telescopes, High Resolution, Mirrors, Proportional Counters, Ray Tracing, Solar X-Rays, Spaceborne Astronomy, Technological Forecasting, Astronomy, X-Ray Telescopes %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/1981tesc.book..195G %B A history of the events leading to the development and flight of the Einstein Observatory is given. The advantages of using grazing-incidence telescopes for solar and extrasolar X-ray astronomy is first discussed and followed by a description of the HEAO program. The Einstein Observatory marks a departure from the manner in which X-ray investigations are carried out, from individual experiments to the shared use of large facilities. The Observatory has achieved a sensitivity to point sources of 10 to the -14th erg/sq cm-sec in the 1-3 keV band, a flux 500 times smaller than previously detected and about 10 million times smaller than that of the first extrasolar source detected in 1962. The design philosophy of the Observatory entails three principles: (1) the unified scientific approach, (2) the establishment of spacecraft requirements at lowest acceptable levels that still allow operating flexibility, and (3) the idea of 'soft' rather than 'hard' failure. The mirror design, including the high resolution imager, the imaging proportional counter, and the solid-state and focal plane crystal spectrometers, is also given. An account of the struggle to gain acceptance by the scientific community and the funding agencies of the need for the Einstein Observatory mission is discussed. Finally, results of observations made by the Observatory are presented in detail, along with plans for future observation experiments. %R 1980ApJ...242L..99H %T Einstein X-ray observations of Proxima Centauri and the surrounding region %A Haisch, B. M.; Harnden, F. R., Jr.; Seward, F. D.; Vaiana, G. S.; Linsky, J. L.; Rosner, R. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics; Astronomical Observatory of Palermo) %J The Astrophysical Journal %V 242 %D 12/1980 %P L99 %L L103 %K Flare Stars, Stellar Coronas, X Ray Astronomy, X Ray Stars, Stellar Envelopes, Stellar Luminosity, Stellar Models, Astronomy %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1980ApJ...242L..99H %B The first detection of both quiescent and flaring soft X-ray emission from a dMe flare star, Proxima Centauri (dM5e) is reported. The data are analyzed for temporal variability and spectral characteristics. The quiescent state is characterized by a mean X-ray luminosity of 1.5 x 10 to the 27th erg s/s, corresponding to a mean surface flux of 700,000 erg s/sq cm-s, and an inferred temperature of 4-million K. The flare that is detected has a peak flux of 7.4 x 10 to the 27th erg s/s and a peak temperature of 17-million K. The implications of these data for models of the quiescent and flare coronae of dMe stars are discussed. %H IOP %Y DOI: 10.1086/183411 %R 1980Natur.287..806S %T Diffuse X-ray emission from the jets of SS433 %A Seward, F.; Grindlay, J.; Seaquist, E.; Gilmore, W. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(University of Toronto, Canada), AD(University of Toronto, Canada) %J Nature %V 287 %D 10/1980 %P 806 %L 808 %K Supernova Remnants, X Ray Sources, Diffuse Radiation, Heao, Periodic Variations, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I PUB_HTML: Publisher Article; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1980Natur.287..806S %B The discovery of strong, variable emission lines¹, which are Doppler-shifted² from SS433, led to the development of a kinematic beam model^3-5 which explains the principal features of the time varying optical spectrum. In this model two opposed jets of material moving outwards from the central star at 0.258c precess with a period of 164 days, about an axis inclined 80° (or 20°) to the line of sight of the observer. The locus of the two beams forms a cone with an opening half angle of 20° (or 80°) (in the model an ambiguity exists between the inclination and cone angles, as the optical data alone cannot distinguish between the two possibilities). A 13-day period observed in the velocity of the `stationary' lines from this object⁶ shows that the system is binary. However, other models exist which also account for the time varying optical spectrum. For example, one model suggests that the Doppler-shifted emission lines originate in a ring of material orbiting a solitary massive black hole⁷. We now report the detection of large-scale X-ray `jets' from SS433. The X-ray emission is diffuse, extending at least 30 arc min from SS433, and is exactly aligned with both SS433 and the bulges of the shell of the huge supernova remnant (SNR) W50. This detection now (1) directly confirms the existence of jets related to SS433, (2) shows the link between SS433 and W50, proving that SS433 is galactic, (3) establishes a minimum age of the jet phenomenon of ~10³ yr, and (4) offers an explanation of why W50 is so much larger than any other known SNR in at least one dimension. The morphology of the diffuse X-ray emission is strikingly similar to that of radio lobes of many extragalactic sources; either in situ heating or particle acceleration is required to explain the appearance of the diffuse X-ray emission. %Y DOI: 10.1038/287806a0 %R 1980BAAS...12..799H %T X-ray Images of the Crab Nebula %A Harnden, F. R., Jr.; Giacconi, R.; Grindlay, J.; Hertz, P.; Schreier, E.; Seward, F.; Tananbaum, H.; van Speybroeck, L. %J Bulletin of the American Astronomical Society %V 12 %D 09/1980 %P 799 %I CITATIONS: Citations to the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1980BAAS...12..799H %R 1980BAAS...12..450M %T Observation of X-Rays from the Jovian System %A Metzger, A. E.; Gilman, D. A.; Luthey, J. L.; Hurley, K. C.; Sullivan, J. D.; Seward, F. D.; Schnopper, H. W. %J Bulletin of the American Astronomical Society %V 12 %D 03/1980 %P 450 %I CITATIONS: Citations to the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1980BAAS...12..450M %R 1980BAAS...12..526K %T Coordinated X-Ray, Optical, and Radio Observations of Flares from the dMe Star YZ Canis Minoris %A Kahler, S. W.; Golub, L.; Harnden, F. R.; Seward, F. D.; Vaiana, G. S. %J Bulletin of the American Astronomical Society %V 12 %D 03/1980 %P 526 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1980BAAS...12..526K %R 1980SAOSR.389..107M %T Preliminary Results of OGS X-Ray Observations of Capella %A Mewe, R.; Gronenschild, E. H. B. M.; Brinkman, A. C.; Dijkstra, J. H.; Schrijver, J.; Heise, J.; Seward, F. D.; Schnopper, H. W.; Delvaille, J. P. %J SAO Special Report %V 389 %D 01/1980 %P 107 %I CITATIONS: Citations to the Article; %I TOC: Table of Contents; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1980SAOSR.389..107M %R 1979msfc.symp..368S %T Einstein observations of extended galactic X-ray sources %A Seward, F. D. %F AA(Smithsonian Astrophysical Observatory) %J Marshall Space Flight Center HEAO Science Symposium %D 11/1979 %P 368 %L 389 %K Galaxies, Heao 2, Spaceborne Telescopes, Supernova Remnants, X Ray Sources, Cassiopeia A, Crab Nebula, Neutron Stars, Spectrum Analysis, Space Radiation %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/1979msfc.symp..368S %B Features of the X-ray pictures taken aboard the space observatory are presented. Imaging proportional counter pictures in three broad X-ray energy ranges were obtained. The X-ray spectrum of supernova remnants is described. %R 1979ApJ...234L..55S %T X-rays from Eta Carinae and the surrounding nebula. %A Seward, F. D.; Forman, W. R.; Giacconi, R.; Griffiths, R. E.; Harnden, F. R., Jr.; Jones, C.; Pye, J. P. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics), AE(Harvard Smithsonian Center for Astrophysics), AF(Harvard Smithsonian Center for Astrophysics), AG(Harvard Smithsonian Center for Astrophysics; University of Leicester, UK) %J The Astrophysical Journal %V 234 %D 11/1979 %P L55 %L L58 %K Early Stars, Nebulae, Stellar Coronas, X Ray Sources, Astrophysics, Stellar Luminosity, Wolf-Rayet Stars, Astrophysics, Carina Nebula:X Rays, Wolf-Rayet Stars:X Rays, X-Ray Sources:Optical Identifications %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1979ApJ...234L..55S %B Two X-ray pictures have been obtained of the Eta Car nebula using the imaging detectors of the Einstein Observatory. One covers a field 1-deg square with a resolution of 1 arcmin; the second covers a field 25 arcmin in diameter with resolution of a few arcsec. These show a region of diffuse X-ray emission with luminosity 10 to the 35th ergs/s. The sources have been positively identified as the peculiar object Eta Car, a Wolf-Rayet star, a cluster of O stars, and five individual O stars. The Eta Car X-ray source is extended and coincides with the outer shell of the diffuse object Eta Car itself. One X-ray bright spot may be emission from a central object within Eta Car. %H IOP %Y DOI: 10.1086/183108 %R 1979ApJ...234L...1G %T A high-sensitivity X-ray survey using the Einstein Observatory and the discrete source contribution to the extragalactic X-ray background. %A Giacconi, R.; Bechtold, J.; Branduardi, G.; Forman, W.; Henry, J. P.; Jones, C.; Kellogg, E.; van der Laan, H.; Liller, W.; Marshall, H.; Murray, S. S.; Pye, J.; Schreier, E.; Sargent, W. L. W.; Seward, F.; Tananbaum, H. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics), AE(Harvard Smithsonian Center for Astrophysics), AF(Harvard Smithsonian Center for Astrophysics), AG(Harvard Smithsonian Center for Astrophysics), AH(Harvard Smithsonian Center for Astrophysics; Leiden Observatory) %J The Astrophysical Journal %V 234 %D 11/1979 %P L1 %L L7 %K Background Radiation, Cosmic Rays, Heao 2, X Ray Sources, Astronomical Observatories, Extraterrestrial Radiation, Sensitivity, Astrophysics, Positions:X-Ray Sources, X-Ray Background, X-Ray Sources:Optical Identifications, X-Ray Sources:Surveys %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1979ApJ...234L...1G %B Surveys of two fields have been carried out utilizing the X-ray imaging instruments of the Einstein Observatory to a limiting flux of 1.3 x 10 to the -14th ergs/sq cm s in the 1-3 keV band, a several hundred-fold increase in sensitivity with respect to previous surveys. Forty-three objects are observed with positional accuracies varying from 5 to 60 arcsec. Optical and radio studies of candidate counterparts are described. The number-intensity relationship for extragalactic sources is evaluated, and the consequences of the findings are discussed with particular emphasis on the discrete source contribution to the extragalactic X-ray background. It is concluded that a large fraction of the background is due to previously unresolved discrete sources. %H IOP %Y DOI: 10.1086/183099 %R 1979BAAS...11..789H %T X-Ray Observations of the Crab Nebula with the Einstein Observatory. %A Harnden, F. R., Jr.; Buehler, B.; Giacconi, R.; Grindlay, J.; Hertz, P.; Schreier, E.; Seward, F.; Tananbaum, H.; van Speybroeck, L. %J Bulletin of the American Astronomical Society %V 11 %D 09/1979 %P 789 %I CITATIONS: Citations to the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1979BAAS...11..789H %R 1979BAAS...11..775H %T On Stars and OB Associations Observed from EINSTEIN. %A Harnden, F. R., Jr.; Golub, L.; Rosner, R.; Seward, F.; Topka, K.; Vaiana, G. S. %J Bulletin of the American Astronomical Society %V 11 %D 09/1979 %P 775 %I CITATIONS: Citations to the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1979BAAS...11..775H %R 1979BAAS...11..796R %T An X-ray Map of the W44 Supernova Remnant from the EINSTEIN Observatory. %A Rolf, D.; Harnden, F. R.; Gorenstein, P.; Pye, J. P.; Seward, F. D.; Willingale, R. %J Bulletin of the American Astronomical Society %V 11 %D 09/1979 %P 796 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1979BAAS...11..796R %R 1979BAAS...11..790P %T An X-ray Map of SN 1006 with the EINSTEIN Observatory. %A Pye, J. P.; Pounds, K. A.; Rolf, D.; Seward, F. D.; Smith, A.; Willingale, R. %J Bulletin of the American Astronomical Society %V 11 %D 09/1979 %P 790 %I CITATIONS: Citations to the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1979BAAS...11..790P %R 1979BAAS...11..609V %T Observations of X-ray sources in M31 with the Einstein Observatory. %A van Speybroeck, L.; Bechtold, J.; Epstein, A.; Forman, W.; Giacconi, R.; Grindlay, J.; Jones, C.; Murray, S.; Schreier, E.; Seward, F. %J Bulletin of the American Astronomical Society %V 11 %D 06/1979 %P 609 %K Andromeda Nebula:X-Ray Sources %I CITATIONS: Citations to the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1979BAAS...11..609V %R 1979ApJ...230..540G %T The Einstein (HEAO 2) X-ray Observatory. %A Giacconi, R.; Branduardi, G.; Briel, U.; Epstein, A.; Fabricant, D.; Feigelson, E.; Forman, W.; Gorenstein, P.; Grindlay, J.; Gursky, H.; Harnden, F. R.; Henry, J. P.; Jones, C.; Kellogg, E.; Koch, D.; Murray, S.; Schreier, E.; Seward, F.; Tananbaum, H.; Topka, K.; Van Speybroeck, L.; Holt, S. S.; Becker, R. H.; Boldt, E. A.; Serlemitsos, P. J.; Clark, G.; Canizares, C.; Markert, T.; Novick, R.; Helfand, D.; Long, K. %F AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics), AE(Harvard Smithsonian Center for Astrophysics), AF(Harvard Smithsonian Center for Astrophysics), AG(Goddard Space Flight Center, Astrophysics Division), AH(Goddard Space Flight Center, Astrophysics Division), AI(Goddard Space Flight Center, Astrophysics Division), AJ(Goddard Space Flight Center, Astrophysics Division) %J The Astrophysical Journal %V 230 %D 06/1979 %P 540 %L 550 %K Heao 2, Spaceborne Astronomy, X Ray Astronomy, Cameras, Focal Plane Devices, High Resolution, Proportional Counters, Spaceborne Telescopes, Spacecraft Instruments, Spectrometers, Astronomy, X-Ray Telescopes %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1979ApJ...230..540G %B The Einstein (HEAO 2) X-ray Observatory, launched in 1978, includes a fully imaging focusing X-ray telescope with an angular resolution of a few arc sec, a field of view of up to one deg, and a sensitivity several hundred times greater than previously available in any X-ray astronomy experiment. A high-resolution imager, an imaging proportional counter, a focal plane crystal spectrometer, and a monitor proportional counter are among the principal instruments on board the Einstein X-ray Observatory. About 20% of the total effective observing time in the first year of the X-ray astronomy experiment has been reserved for guest observers. %H IOP %Y DOI: 10.1086/157110 %R 1979BAAS...11..424H %T Observations of the Vela Pulsar from the Einstein Observatory %A Harnden, F. R., Jr.; Hertz, P.; Gorenstein, P.; Grindlay, J.; Schreier, E.; Seward, F. %J Bulletin of the American Astronomical Society %V 11 %D 03/1979 %P 424 %I CITATIONS: Citations to the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1979BAAS...11..424H %R 1979BAAS...11..446V %T Initial Results from the Einstein Survey of Stellar Low-Luminosity X-ray Sources %A Vaiana, G.; Forman, W.; Giacconi, R.; Gorenstein, P.; Pye, J.; Rosner, R.; Seward, F.; Topka, K. %J Bulletin of the American Astronomical Society %V 11 %D 03/1979 %P 446 %I CITATIONS: Citations to the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1979BAAS...11..446V %R 1979BAAS...11..446R %T X-Ray Sources from O Star Associations %A Rosner, R.; Grindlay, G.; Harnden, R.; Seward, F.; Vaiana, G. %J Bulletin of the American Astronomical Society %V 11 %D 03/1979 %P 446 %I CITATIONS: Citations to the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1979BAAS...11..446R %R 1979BAAS...11..462G %T A High Resolution X-Ray Image of the Remnant of Tycho's Supernova from the Einstein Observatory %A Gorenstein, P.; Murray, S.; Epstein, A.; Griffiths, R.; Fabbiano, G.; Seward, F. %J Bulletin of the American Astronomical Society %V 11 %D 03/1979 %P 462 %I CITATIONS: Citations to the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1979BAAS...11..462G %R 1979BAAS...11..442M %T X-ray Surveys Using Einstein: A Medium Sensitivity Survey and Spectra of "Deep Survey" Sources %A Marshall, H.; Seward, F.; Schwartz, D.; Giacconi, R. %J Bulletin of the American Astronomical Society %V 11 %D 03/1979 %P 442 %I CITATIONS: Citations to the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1979BAAS...11..442M %R 1979BAAS...11..424T %T X-Ray Observations of the Crab Nebula with the Einstein Observatory %A Tananbaum, H.; Epstein, A.; Forman, W.; Giacconi, R.; Grindlay, J.; Harden, F. R., Jr.; Jones, C.; Schreier, E.; Seward, F.; van Speybroeck, L. %J Bulletin of the American Astronomical Society %V 11 %D 03/1979 %P 424 %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1979BAAS...11..424T %R 1978IAUC.3309....2G %T HEAO 2 %A Giacconi, R.; Seward, F. %J International Astronomical Union Circular %V 3309 %D 11/1978 %P 2 %I ABSTRACT: Abstract; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1978IAUC.3309....2G %B On behalf of the Scientific Consortium, R. Giacconi informs us that the Einstein ObservatorY (HEAO 2) was successfully launched on Nov. 13d05h24m UT. The orbit is circular and nominal: Incl. = 23o.5, P = 95 min, altitude = 535 km. All instrumentation has been activated, and backgrounds and performance are nominal. The spacecraft is pointing and maneuvering well. Only the high-resolution imager (HRI) has been at the telescope focus. Bright sources have been observed, and the images are as expected. Observatory activation will take two months: each instrument will be at the focus for two weeks. The planned observing program, including Guest Observations, is expected to start during the first week of 1979 Jan. Details concerning the instruments and the observing program can be obtained by writing to F. Seward at the address: Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, U.S.A. %R 1978IAUC.3245....1S %T HEAO B %A Seward, F. D. %J International Astronomical Union Circular %V 3245 %D 07/1978 %P 1 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1978IAUC.3245....1S %B F. D. Seward writes: "The HEAO-B satellite, scheduled for launch in November, will carry the first large x-ray telescope and will perform astronomical observations In the energy range 0.2-4 keV. Either of two imaging instruments or two spectrometers can be positioned at the focus. The spatial resolution is 2" for strong sources. Twenty percent of the useful observing time during the first year will be available for guest observations. There are also opportunities to collaborate by participating in joint radio/optical/x-ray observations or in the analysis of the x-ray data. Proposals for guest observations are being evaluated by a NASA selection committee (meeting four times per year). Details for submission of proposals are given in a Space Science Notice dated June 7. Details concerning the instruments carried by HEAO B and the planned observing program can be obtained from me at the address: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, NA 02138, U.S.A. (telephone 617-495-7282)." %R 1978JBIS...31...83S %T A trip to the Crab Nebula. %A Seward, F. D. %F AA(Smithsonian Astrophysical Observatory) %J Journal of the British Interplanetary Society %V 31 %D 03/1978 %P 83 %L 92 %K Crab Nebula, Pulsars, Radiation Sources, Supernovae, Background Radiation, Radiation Hazards, Supernova Remnants, Space Sciences (General), Crab Nebula %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %U https://ui.adsabs.harvard.edu/abs/1978JBIS...31...83S %B The Crab Nebula and the processes occurring in it have long occupied the attention of the world's astrophysicists. Because so many observations of this Nebula have been made, physical conditions inside it can be calculated. In this paper, we assume that the earth is transported to a point inside the Crab Nebula, and we compare the environment there with the environment here. We do this to illustrate the unusual nature of this Nebula and its pulsar, and to point out how fortunate we are to be located far from recent supernovae and their remnants. %R 1978MNRAS.182..489C %T The Ariel V (SSI) catalogue of high galactic latitude ( %A Cooke, B. A.; Ricketts, M. J.; Maccacaro, T.; Pye, J. P.; Elvis, M.; Watson, M. G.; Griffiths, R. E.; Pounds, K. A.; McHardy, I.; Maccagni, D.; Seward, F. D.; Page, C. G.; Turner, M. J. L. %F AA(University of Leicester, UK), AB(University of Leicester, UK), AC(University of Leicester, UK), AD(University of Leicester, UK), AE(University of Leicester, UK), AF(University of Leicester, UK), AG(University of Leicester, UK), AH(University of Leicester, UK) %J Monthly Notices of the Royal Astronomical Society %V 182 %D 02/1978 %P 489 %L 515 %K Ariel 5 Satellite, Astronomical Catalogs, Cosmic X Rays, Milky Way Galaxy, X Ray Astronomy, Data Processing, Galactic Clusters, Luminous Intensity, Sky Surveys (Astronomy), Spaceborne Astronomy, X Ray Sources, Astronomy, Catalogues:X-Ray Sources, X-Ray Sources: Optical Identifications %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I PUB_HTML: Publisher Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %I CDS: Strasbourg Astronomical Data Center; %U https://ui.adsabs.harvard.edu/abs/1978MNRAS.182..489C %B The 2A catalog is the result of 10,000 orbits of observation by the Sky Survey Instrument on the Ariel 5 satellite and contains 105 X-ray sources with galactic latitudes higher than + or - 10 deg. The procedures and criteria used in establishing these sources and measuring their intensities and positions are described. As a consequence of the comparatively small error boxes (0.1 to 0.5 square degree) and the sensitivity limit of the survey (90 percent of the sky to better than 1.2 Ariel count/s or approximately 3.2 Uhuru count/s), optical identifications are suggested. %H OUP %Y DOI: 10.1093/mnras/182.3.489 %R 1978ApJ...219L..17Z %T The X-Ray Spectrum and Structure of the Puppis a Supernova Remnant %A Zarnecki, J. C.; Culhane, J. L.; Toor, A.; Seward, F. D.; Charles, P. A. %J The Astrophysical Journal %V 219 %D 01/1978 %P L17 %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1978ApJ...219L..17Z %H IOP %Y DOI: 10.1086/182598 %R 1977PASP...89..696S %T Was the bright transient X-ray source Centaurus XR-4 I a globular cluster? %A Seward, F. D.; Liller, W. %J Publications of the Astronomical Society of the Pacific %V 89 %D 10/1977 %P 696 %L 698 %K Globular Clusters:X-Ray Sources, X-Ray Sources: Transient %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1977PASP...89..696S %B The globular cluster NCC 5824 lies within the error box of the transient X-ray source Cen XR-4. The characteristics of the cluster make it a likely a candidate for a globular cluster X-ray source. Observations of the transient X-ray source and the characteristics of the globular cluster are briefly reviewed. If the source originated in the globular cluster, the maximum X-ray luminosity was 3 X 1040 erg , two orders of magnitude more luminous than any other observed galactic or globular cluster X-ray source. The implication of this result is that a massive black hole might exist within the cluster. Key words: X-ray sources-globular clusters %H IOP %Y DOI: 10.1086/130211 %R 1977ApJ...216..560T %T Observation of X-rays from the Crab pulsar. %A Toor, A.; Seward, F. D. %F AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California) %J The Astrophysical Journal %V 216 %D 09/1977 %P 560 %L 564 %K Crab Nebula, Neutron Stars, Pulsars, X Ray Sources, Black Body Radiation, Lunar Occultation, Photons, Spectral Energy Distribution, X Ray Astronomy, Astronomy %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1977ApJ...216..560T %B A measurement of the pulsed X-ray emission from the Crab Nebula made during a lunar occultation is presented. Comparison is made with previous observations, and possible variations in this pulsed emission are discussed. %H IOP %Y DOI: 10.1086/155497 %R 1977MNRAS.180P..75G %T Observations of the LMC X-ray sources with the Ariel V Sky Survey Instrument. %A Griffiths, R. E.; Seward, F. D. %F AA(University of Leicester, UK) %J Monthly Notices of the Royal Astronomical Society %V 180 %D 08/1977 %P 75P %L 79 %K Galactic Radiation, Luminous Intensity, Magellanic Clouds, Sky Surveys (Astronomy), X Ray Sources, Astronomical Maps, Satellite Observation, Spaceborne Astronomy, X Ray Astronomy, Astronomy %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I PUB_HTML: Publisher Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1977MNRAS.180P..75G %B Summary. Long-term X-ray light curves are presented for the X.ray sources in the Large Magellanic Cloud, as obtained by the Leicester University Sky Survey Instrument on board the Ariel V spacecraft. The five previously known sources have all been detected. Evidence is presented for a sixth source possibly associated with the LMC. Ml sources are variable but no regular periodic behaviour has been observed. LMC X-l and X-2 vary a factor of 2 or 3, LMC X-3 and X-4 were observed to vary by a factor of at least 7, and LMC X-5 and X-6 varied from just above to below our threshold of detectability. %H OUP %Y DOI: 10.1093/mnras/180.1.75P %R 1976Natur.264..421S %T Argon fluorescent X rays in the Earth's atmosphere during solar flares %A Seward, F. D.; Horton, B.; Pollard, G.; Sanford, P. W. %F AA(University College London, UK), AB(University College London, UK), AC(University College London, UK) %J Nature %V 264 %D 12/1976 %P 421 %L 423 %K Argon, Earth Albedo, Earth Atmosphere, Radiant Flux Density, Solar Flares, X Ray Fluorescence, Ariel 5 Satellite, Atmospheric Composition, Energy Spectra, Proportional Counters, Solar X-Rays, X Ray Scattering, Geophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1976Natur.264..421S %B THE satellite Ariel V carries a proportional counter pointed along the spin axis. We report here the detection of a strong flux of X rays coming from the sunlit Earth during two large solar flares. These albedo X rays are proportional to the solar X-ray flux and consist of scattered X rays and a strong fluorescent line at 3 keV from atmospheric argon. There is also a weaker line at ~ 7 keV which is probably present in the incident solar spectrum. %Y DOI: 10.1038/264421a0 %R 1976MNRAS.177P..13S %T X-ray sources in the southern Milky Way. %A Seward, F. D.; Page, C. G.; Turner, M. J. L.; Pounds, K. A. %F AA(University of Leicester, UK), AB(University of Leicester, UK), AC(University of Leicester, UK), AD(University of Leicester, UK) %J Monthly Notices of the Royal Astronomical Society %V 177 %D 10/1976 %P 13P %L 20 %K Milky Way Galaxy, Supernova Remnants, Variable Stars, X Ray Sources, Astronomical Catalogs, Astronomical Maps, Error Analysis, Satellite- Borne Instruments, Sky Surveys (Astronomy), Tables (Data), Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1976MNRAS.177P..13S %B The Ariel V sky-survey detectors have been used to study X-ray sources within 15 deg of the galactic plane between 255 and 340 deg galactic longitude. Fourteen new sources have been found, and locations and strengths are derived. Strengths are also given for 27 sources discovered in previous surveys which have been definitely detected by Ariel V. Ten previously detected sources were not visible in the present survey. One new source is possibly associated with the variable star Eta Carinae or with a nearby supernova remnant. %H OUP %Y DOI: 10.1093/mnras/177.1.13P %R 1976PlPh...18..675H %T Implosion experiments with an asymmetrically irradiated laser fusion target %A Holzrichter, J. F.; Ahlstrom, H. G.; Speck, D. R.; Storm, E.; Swain, J. E.; Coleman, L. W.; Hendricks, C. D.; Kornblum, H. N.; Seward, F. D.; Slivinsky, V. W. %F AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California), AC(Lawrence Livermore National Laboratory, California), AD(Lawrence Livermore National Laboratory, California), AE(Lawrence Livermore National Laboratory, California), AF(Lawrence Livermore National Laboratory, California), AG(Lawrence Livermore National Laboratory, California), AH(Lawrence Livermore National Laboratory, California), AI(Lawrence Livermore National Laboratory, California), AJ(Lawrence Livermore National Laboratory, California) %J Plasma Physics %V 18 %D 09/1976 %P 675 %L 680 %K Deuterium Plasma, Fusion Reactors, Laser Fusion, Plasma Heating, Compressible Fluids, Implosions, Neodymium Lasers, Reactor Technology, Tritium, Plasma Physics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1976PlPh...18..675H %B A single neodymium glass laser beam was used to implode a spherical glass microsphere filled with DT gas. The outer surface of the microshell was ablated and the shell was shocked and accelerated inward. During the implosion, rapid internal heating of the glass shell by electrons and X-rays caused the glass to decompress. The DT gas was compressed and heated to fusion conditions by the inward moving component of the glass shell. Volume compression ratios of 50-100 fold and 10 to the 4th MeV neutrons were observed. %Y DOI: 10.1088/0032-1028/18/9/002 %R 1976BAAS....8..529C %T The X-ray Temperature of Puppis A. %A Charles, P. A.; Culhane, J. L.; Zarnecki, J. C.; Seward, F. D.; Toor, A. %J Bulletin of the American Astronomical Society %V 8 %D 09/1976 %P 529 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1976BAAS....8..529C %R 1976ApJ...207...96T %T Evidence for "thermal" X-rays from the Crab nebula. %A Toor, A.; Palmieri, T. M.; Seward, F. D. %F AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California), AC(Lawrence Livermore National Laboratory, California) %J The Astrophysical Journal %V 207 %D 07/1976 %P 96 %L 101 %K Crab Nebula, Lunar Occultation, Pulsars, Rocket-Borne Instruments, Supernova Remnants, X Ray Sources, Astronomical Models, Interstellar Matter, Point Sources, Radio Sources (Astronomy), Spectrum Analysis, X Ray Scattering, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1976ApJ...207...96T %B Data obtained during a recent lunar occultation are presented which indicate the existence of a weak soft X-ray source close to or within the Crab Nebula. Several interpretations of the weak source are considered, including a weak point source in the field of view, scattering of X-rays by interstellar dust along the line of sight, and an extended source associated with the expanding filaments of the nebula. The data are analyzed in terms of each model, and it is found that the source should be placed within the nebula itself. Based on this result, it is suggested that the nebular X-ray emission originates in two areas: a strong nonthermal source surrounding the pulsar and an extended 'thermal' source associated with the expanding filaments and the outer regions of the radio source. It is noted that the predicted luminosity and spectrum of the thermal source are compatible with the X-ray characteristics of other young supernova remnants, specifically Cas A and Tycho. %H IOP %Y DOI: 10.1086/154471 %R 1976BAAS....8..443S %T X-ray Sources in the Aquilla-Serpens-Scutum Region %A Seward, F. D.; Page, C. G.; Turner, M. J.; Pounds, K. A. %J Bulletin of the American Astronomical Society %V 8 %D 06/1976 %P 443 %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1976BAAS....8..443S %R 1976MNRAS.175P..39S %T X-ray sources in the Aquila-Serpens-Scutum region. %A Seward, F. D.; Page, C. G.; Turner, M. J. L.; Pounds, K. A. %F AA(University of Leicester, UK), AB(University of Leicester, UK), AC(University of Leicester, UK), AD(University of Leicester, UK) %J Monthly Notices of the Royal Astronomical Society %V 175 %D 05/1976 %P 39P %L 46 %K Galactic Radiation, Satellite Observation, X Ray Sources, Ariel Satellites, Data Reduction, Graphs (Charts), Sky Surveys (Astronomy), Supernova Remnants, Uhuru Satellite, Astronomy %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I PUB_HTML: Publisher Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1976MNRAS.175P..39S %B The Ariel-5 sky survey detectors have been used to study X-ray sources within 10 deg of the galactic plane between longitudes 20 deg and 55 deg. Seventeen sources have been found and locations and strengths derived. These are compared with results of previous surveys. Seven of these sources were already known and this observation yields an improved position for four of them. Ten of the sources are new. One is possibly associated with the globular cluster NGC 6712, and one with the supernova remnant, W50. %H OUP %Y DOI: 10.1093/mnras/175.1.39P %R 1976RScI...47..464S %T Calibrated ''four-color'' x-ray microscope for laser plasma diagnostics %A Seward, F.; Dent, J.; Boyle, M.; Koppel, L.; Harper, T.; Stoering, P.; Toor, A. %F AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California), AC(Lawrence Livermore National Laboratory, California), AD(Lawrence Livermore National Laboratory, California), AE(Lawrence Livermore National Laboratory, California), AF(Lawrence Livermore National Laboratory, California), AG(Lawrence Livermore National Laboratory, California) %J Review of Scientific Instruments %V 47 %D 04/1976 %P 464 %L 470 %K Laser Fusion, Laser Plasmas, Microscopy, Plasma Diagnostics, X Ray Apparatus, Calibrating, Electromagnetic Wave Filters, Energy Spectra, Mirrors, Radiography, X Ray Spectra, Instrumentation and Photography, 52.70.Kz, Optical measurements %C 1976: American Institute of Physics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1976RScI...47..464S %B Four quartz, orthogonal, cylindrical mirror pairs, two of which are coated with nickel, image the x-ray emission from laser fusion targets on hard film with a magnification of 3. K-edge filters used in conjunction with the mirror pairs permit us to take simultaneous pictures in four energy bands between 0.7 and 3.5 keV. We have measured microscope resolution, mirror reflection efficiency, and film sensitivity and used them to deduce the absolute emissivity and spectral characteristics of various laser fusion targets. This instrument is now used routinely for studying laser-generated plasmas at Lawrence Livermore Laboratory. %H AIP %Y DOI: 10.1063/1.1134656 %R 1976ApJ...205..238S %T An empirical comparison of X-ray and radio emission from supernova remnants. %A Seward, F.; Burginyon, G.; Grader, R.; Hill, R.; Palmieri, T.; Stoering, P.; Toor, A. %F AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California), AC(Lawrence Livermore National Laboratory, California), AD(Lawrence Livermore National Laboratory, California), AE(Lawrence Livermore National Laboratory, California), AF(Lawrence Livermore National Laboratory, California), AG(Lawrence Livermore National Laboratory, California) %J The Astrophysical Journal %V 205 %D 04/1976 %P 238 %L 246 %K Astronomical Catalogs, Radio Emission, Supernova Remnants, X Ray Sources, Luminosity, Radio Sources (Astronomy), Rocket Sounding, Statistical Correlation, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1976ApJ...205..238S %B Data from several rocket flights are combined to list upper limits to soft X-ray emission from supernova remnants (SNRs). These limits are compared with observations of SNRs that are known X-ray emitters. There is no strong correlation between measured radio and X-ray flux at the top of the atmosphere. X-ray luminosities and upper limits are calculated for all SNR that are bright radio sources. The ratio between X-ray and radio luminosity is found to be in the range from 20 to 2000. The dependence of SNR luminosity on diameter is discussed. %H IOP %Y DOI: 10.1086/154269 %R 1976ssae.conf..355F %T X-ray and gamma-ray astronomy. %A Fichtel, C. E.; Mumford, G. S.; Lindquist, T. R.; Webber, W. R.; Seward, F. D.; Page, T.; Jones, C.; Forman, W.; Liller, W. %J Space Science and Astronomy. Escape from Earth %D 01/1976 %P 355 %L 386 %U https://ui.adsabs.harvard.edu/abs/1976ssae.conf..355F %R 1975ApJ...202..494P %T Spatial distribution of X-rays in the Crab nebula. %A Palmieri, T. M.; Seward, F. D.; Toor, A.; van Flandern, T. C. %F AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California), AC(Lawrence Livermore National Laboratory, California), AD(U.S. Naval Observatory, Washington, D.C.) %J The Astrophysical Journal %V 202 %D 12/1975 %P 494 %L 497 %K Crab Nebula, Lunar Occultation, Radiation Distribution, Supernovae, X Ray Astronomy, Pulsars, Radiant Flux Density, Radiation Sources, Spatial Distribution, Stellar Luminosity, Astronomy %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1975ApJ...202..494P %B X-ray measurements made during a lunar occulation of the Crab Nebula show that the spatial extent of the source is about 100" in the east-west direction. The center of the X-ray emitting region is about 8" west of the pulsar. The shape is basically the same when viewed in several energy intervals from 0.5 to 16 keV. The size does not change by more than 30 percent over this energy range. Optical and X-ray intensity distributions are compared, and no optical features other than the pulsar are obvious in the X-ray data. Subject headings: Crab Nebula - occultations supernova remnants - X-ray sources %H IOP %Y DOI: 10.1086/153998 %R 1975aps..meet...10B %T X-ray microscopy of laser fusion targets in four energy bands from 0.7 to 4.0 keV %A Boyle, M. J.; Seward, F. D.; Harper, T. L.; Koppel, L. N.; Pettipiece, K. J.; Ahlstrom, H. G. %F AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California), AC(Lawrence Livermore National Laboratory, California), AD(Lawrence Livermore National Laboratory, California), AE(Lawrence Livermore National Laboratory, California), AF(Lawrence Livermore National Laboratory, California) %J Presented at APS Meeting %D 10/1975 %P 10 %L 14 %K Laser Fusion, Laser Plasmas, X Ray Analysis, Calibrating, Microscopy, Photographs, Radiation Measurement, Spatial Distribution, Spectral Energy Distribution, X Ray Spectra, Lasers and Masers %I ABSTRACT: Abstract; %U https://ui.adsabs.harvard.edu/abs/1975aps..meet...10B %B A grazing X-ray microscope was shown to be able to photograph the X-ray emission from laser-produced plasmas between 0.8 and 4.0 keV with a spatial resolution of approximately 3 microns. The calibration of the X-ray mirror energy response functions and the X-ray film allow absolute measurements of the spatial and spectral distribution of the X-ray emission from laser fusion targets. %R 1975ApJ...200..709H %T A soft X-ray survey of the Scutum-Serpens-Aquila region. %A Hill, R. W.; Burginyon, G. A.; Seward, F. D. %J The Astrophysical Journal %V 200 %D 09/1975 %P 709 %L 714 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1975ApJ...200..709H %B Data from a 1973 June 23 rocket flight are presented and discussed. Soft X-ray spectra of the sources GX 17+2 and Ser Xl together with the best-fit model spectra are given. We derive a location of Ser X-l which confirms that listed in the 3U catalog. Upper limits are set to the X-ray flux from eight supernova remnants, and upper limits to their X-ray luminosity are calculated. Spatial structure in the diffuse soft X-ray background was observed. A map of the diffuse background in this region is derived. Subject headings: interstellar matter - supernova remnants - X-ray sources %H IOP %Y DOI: 10.1086/153841 %R 1975ApJ...200..163B %T Analysis of X-ray spectra reveals possibility of enhanced silicon in three supernova remnants. %A Burginyon, G. A.; Hill, R. W.; Seward, F. D. %F AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California), AC(Lawrence Livermore National Laboratory, California) %J The Astrophysical Journal %V 200 %D 08/1975 %P 163 %L 170 %K Abundance, Plasma Radiation, Silicon, Supernova Remnants, X Ray Spectra, High Temperature Plasmas, Interstellar Matter, Spectrum Analysis, X Ray Astronomy, Astrophysics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1975ApJ...200..163B %B New calculations by Tucker and Koren for X-radiation from a thin hot plasma are applied to observed X-ray spectra of the Cygnus Loop, Vela X, and Puppis A. These calculations cannot satisfactorily describe the spectra of these three old supernova remnants when evaluated at one temperature and for commonly accepted cosmic abundances. However, all of the data are fitted when just two abundance values are changed: an increase in silicon by a factor of approximately 10, and a factor of 5 less iron. This modified set of abundances substituted into Tucker and Koren's model agrees with recent optical coronal line observations in the Cygnus Loop and explains spectra from recent observations of the supernova remnants Cas A and Tycho. It is remarkable that this thermal model with modified abundances fits the spectra of all these objects. Subject headings: abundances, nebular - spectra, X-ray - supernova remnants %H IOP %Y DOI: 10.1086/153773 %R 1975ApJ...200..158H %T The Soft X-Ray Spectra of Cassiopeia a and Tycho's Supernova Remnant %A Hill, R. W.; Burginyon, G. A.; Seward, F. D. %J The Astrophysical Journal %V 200 %D 08/1975 %P 158 %L 162 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1975ApJ...200..158H %B The X-ray spectra of Tycho's supernova remnant and Cas A have been measured with good statistics. Both spectra show evidence for silicon line emission. The thermal model of Tucker and Koren has been used to fit both spectra. To obtain a satisfactory fit to the data with this model, the silicon abundance must be increased about 10 times from the usual cosmic abundance values. Neither spectrum can be fitted with exponential or power4aw models without the addition of line emission. Tycho's remnant shows very little soft X-ray absorption. Subject headings: abundances, nebular - spectra, X-ray - supernova remnants %H IOP %Y DOI: 10.1086/153772 %R 1975BAAS....7..456T %T A Possible Extended Soft X-Ray Component of the Crab Nebula %A Toor, A.; Palmieri, T. M.; Seward, F. D. %J Bulletin of the American Astronomical Society %V 7 %D 06/1975 %P 456 %I CITATIONS: Citations to the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1975BAAS....7..456T %R 1975BAAS....7..246H %T The Soft X-ray Spectra of Cas A and Tycho's Supernova Remnant. %A Hill, R. W.; Burginyon, G. A.; Seward, F. D. %J Bulletin of the American Astronomical Society %V 7 %D 03/1975 %P 246 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1975BAAS....7..246H %R 1975BAAS....7..247T %T Crab Nebula X-ray Lunar Occultation. %A Toor, A.; Palmieri, T.; Seward, F. %J Bulletin of the American Astronomical Society %V 7 %D 03/1975 %P 247 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1975BAAS....7..247T %R 1975RScI...46..204S %T A simple x-ray microscope for photographing laser produced plasmas %A Seward, F. D.; Palmieri, T. M. %F AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California) %J Review of Scientific Instruments %V 46 %D 02/1975 %P 204 %L 206 %K High Resolution, Laser Plasmas, Microscopes, Radiography, X Ray Apparatus, Calibrating, Lens Design, Photosensitivity, Plasma Radiation, Spherical Shells, Instrumentation and Photography, 52.70.-m, 52.50.Jm, 07.85.+n, Plasma diagnostic techniques and instrumentation, Plasma production and heating by laser beams %C 1975: American Institute of Physics %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1975RScI...46..204S %B We have built two simple x-ray microscopes and have used these instruments to take x-ray pictures of laser produced plasmas. The sensitive range is 0.2 -8 keV with greatest sensitivity from approximately 0.5-2 keV. For low energy x rays the resolution is better than that which can be obtained with a pinhole camera. %H AIP %Y DOI: 10.1063/1.1134167 %R 1975xris.conf..975B %T Adaptation of recent thermal model calculations to X-ray spectra of three old supernova remnants %A Burginyon, G. A.; Hill, R. W.; Seward, F. D. %F AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California), AC(Lawrence Livermore National Laboratory, California) %J X-Rays in Space - Cosmic, Solar, and Auroral X-Rays, Volume 1 %V 2 %D 01/1975 %P 975 %L 984 %K Abundance, Astronomical Models, Energy Spectra, Supernova Remnants, Thermal Radiation, X Ray Spectra, Atomic Spectra, Chemical Composition, Emission Spectra, Line Spectra, Optical Properties, Solar Corona, Astrophysics %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/1975xris.conf..975B %R 1975xris.conf.1121S %T Joint cosmic/auroral X-ray panel discussion %A Seward, F. D. %F AA(Lawrence Livermore National Laboratory, California) %J X-Rays in Space - Cosmic, Solar, and Auroral X-Rays, Volume 1 %V 2 %D 01/1975 %P 1121 %L 1126 %K Auroral Zones, Electron Precipitation, X Ray Astronomy, Background Radiation, Electron Counters, Electron Flux Density, Geomagnetism, Radiant Flux Density, Radiation Detectors, Rocket Sounding, Satellite Observation, Space Radiation %I ABSTRACT: Abstract; %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/1975xris.conf.1121S %B The effects on X-ray observations due to low-latitude precipitating electrons having energies between 10 and 100 keV are considered, and characteristics of the low-latitude soft electron flux are described. It is shown that the electron background prevents the determination of weak features in soft X-ray observations. Sounding-rocket data are presented which indicate that the soft electron flux is usually at a maximum when detectors are aligned perpendicular to the geomagnetic field lines, and that quasi-trapped electrons have a steep altitude dependence while those parallel to the magnetic field have a much flatter altitude dependence. The most electron-free region is found to be the hemisphere bounded by the perpendicular to the field lines and facing toward the earth. %R 1975xris.conf..378S %T A review of soft X-ray astronomy %A Seward, F. D. %F AA(Lawrence Livermore National Laboratory, California) %J X-Rays in Space - Cosmic, Solar, and Auroral X-Rays, Volume 1 %V 1 %D 01/1975 %P 378 %L 399 %K Interstellar Extinction, Pulsars, Spaceborne Astronomy, X Ray Absorption, X Ray Astronomy, Background Radiation, Diffuse Radiation, Energy Spectra, Interstellar Matter, Milky Way Galaxy, Satellite Observation, Uhuru Satellite, Astronomy %I ABSTRACT: Abstract; %I Co-Reads: Co-Reads; %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/1975xris.conf..378S %B Developments and problems in soft (200 eV to 2 keV) X-ray astronomy are reviewed. The distribution of X-ray sources in the galaxy as determined from UHURU data is described, and the properties of three strong sources of soft X-rays (Cygnus Loop, Vela X, Puppis A) are summarized. The problem of X-ray absorption in the interstellar medium is discussed, the absolute luminosity of several discrete sources is determined, and results are considered for soft X-ray absorption measurements of the Crab pulsars. The existence of a diffuse soft X-ray background is noted. %R 1975xris.conf.1175S %T Summary - Cosmic X-rays %A Seward, F. D. %F AA(Lawrence Livermore National Laboratory, California) %J X-Rays in Space - Cosmic, Solar, and Auroral X-Rays, Volume 1 %V 2 %D 01/1975 %P 1175 %L 1186 %K Background Noise, Cosmic Rays, X Ray Astronomy, X Ray Sources, Binary Stars, Galactic Radiation, Gamma Rays, Solar X-Rays, Supernova Remnants, Surveys, Terrestrial Radiation, Space Radiation %I ABSTRACT: Abstract; %I TOC: Table of Contents; %U https://ui.adsabs.harvard.edu/abs/1975xris.conf.1175S %B Observational developments in X-ray astronomy are summarized. Surveys of the hard and soft X-ray skies are outlined, and the problem of background noise in soft X-ray surveys is discussed. The various types of discrete X-ray sources are described, including supernova remnants, binary sources, extragalactic objects and systems, and transient flare sources. The peculiar properties of gamma bursts are briefly noted, the characteristics of solar X-ray flares are reviewed, and X-ray emission from the earth's auroral regions is considered. %R 1974AJ.....79..995T %T The Crab nebula as a calibration source for X-ray astronomy. %A Toor, A.; Seward, F. D. %F AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California) %J The Astronomical Journal %V 79 %D 10/1974 %P 995 %L 999 %K Calibrating, Crab Nebula, X Ray Astronomy, X Ray Spectra, Energy Spectra, Pulsars, Spectrum Analysis, X Ray Sources, Astronomy %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1974AJ.....79..995T %B A new high-quality observation of the 2- to 60-keV spectrum of the Crab Nebula is presented. Previous x-ray spectral measurements are critically reviewed and compared with this new measurement. Within the accuracy of the observations, which span a period of eight years, the Crab can be considered a steady x-ray source, producing a constant spectrum suitable for checking the response of x-ray instruments. %H IOP %Y DOI: 10.1086/111643 %R 1974ApJ...189L..69H %T An Unusual X-Ray Source in Scutum %A Hill, R.; Burginyon, G.; Grader, R.; Toor, A.; Stoering, J.; Seward, F. %J The Astrophysical Journal %V 189 %D 04/1974 %P L69 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1974ApJ...189L..69H %B Two previously unreported X-ray sources have been observed. The spectrum of one of them, Sct X-1 (111 = 24?41), shows the strongest absorption of any source that we have ever observed. Both sources are probably variable. Subject headings: spectra, X-ray - X-ray sources %H IOP %Y DOI: 10.1086/181466 %R 1974BAAS....6Q.272H %T X-ray Survey of Scutum - Aquila Region %A Hill, D. W.; Burginyon, G.; Grader, R.; Stoering, J. P.; Seward, F. D.; Toor, A. %J Bulletin of the American Astronomical Society %V 6 %D 03/1974 %P 272 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1974BAAS....6Q.272H %R 1974ApJ...187..505H %T A Search for Soft X-Ray Sources in the Galactic Anticenter. Absorption of X-Rays from the Crab Nebula %A Hill, R. W.; Burginyon, G. A.; Seward, F. D.; Stoering, J. P.; Toor, A. %J The Astrophysical Journal %V 187 %D 02/1974 %P 505 %L 510 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1974ApJ...187..505H %B Results are presented from the third part of a three-part survey of the galactic plane for cosmic X-ray sources in the energy range 0.2-18 keV. This part of the survey covers the region from Cassiopeia to Puppis, galactic longitudes 1 . The sources detected by the experiment were Cas A, the Crab Nebula, Vel X, and Pup A. Spectral parameters were derived for the Crab using a power-law photon spectrum: Np=CE exp( an ), where a = 2.0 1 0.1 and flH = (2.0 1 0.3) x 1021 hydrogen atoms em- Upper limits are given for the intensities of several other supernova remnants scanned during the experiment. Subject headings: interstellar matter - X-ray sources %H IOP %Y DOI: 10.1086/152660 %R 1974ecxa.confE...3S %T The geographical distribution of ≡ 100-keV electrons above the earth's atmosphere. %A Seward, F. D. %J Electron Contamination in X-ray Astronomy Experiments %D 01/1974 %P 3 %U https://ui.adsabs.harvard.edu/abs/1974ecxa.confE...3S %R 1974ecxa.confE...1S %T Electrons at low altitudes: a difficult background problem for soft X-ray astronomy. %A Seward, F. D.; Grader, R. J.; Toor, A.; Burginyon, G. A.; Hill, R. W. %J Electron Contamination in X-ray Astronomy Experiments %D 01/1974 %P 1 %I CITATIONS: Citations to the Article; %U https://ui.adsabs.harvard.edu/abs/1974ecxa.confE...1S %R 1973ApJ...182..411P %T Observations of soft X-rays: Upper limits on the flux from SN 1972E and measurements of the diffuse background in Centaurus. %A Palmieri, T. M.; Burginyon, G. A.; Hill, R. W.; Scudder, J. K.; Seward, F. D.; Toor, A. %J The Astrophysical Journal %V 182 %D 06/1973 %P 411 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %U https://ui.adsabs.harvard.edu/abs/1973ApJ...182..411P %B An attempt was made to measure soft X-rays from SN 1972E. The resulting upper limit shows that 19 days after discovery, the X-ray luminosity was not greater than 10 percent of the optical luminosity. Measurements of the background in the surrounding region show that a localized enhancement, observed previously, dominates the diffuse flux in this area. Two maps give the spatial dependence of the diffuse flux in the energy ranges 0.20.6 keV and 0.61.6 keV. Subject headings: supernovae - X-rays %H IOP %Y DOI: 10.1086/152149 %R 1973S&T....45..220S %T The Distribution of X-Ray Sources in Our Galaxy %A Seward, Frederick D. %J Sky and Telescope %V 45 %D 04/1973 %P 220 %U https://ui.adsabs.harvard.edu/abs/1973S&T....45..220S %R 1973ApJ...180L..75B %T Observation of Structure in the X-Ray Spectrum of Puppis a %A Burginyon, G.; Hill, R.; Seward, F.; Tarter, B.; Toor, A. %J The Astrophysical Journal %V 180 %D 03/1973 %P L75 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1973ApJ...180L..75B %B X-ray data from two rocket flights which scanned Puppis A show prominent structure in the energy spectrum that cannot be explained by continuum models alone. The spectral observations are well fitted by combining the effects of line radiation, radiative recombination, and bremsstrahlung from the thermal source. Subject headings: X-ray sources - spectra, X-ray %H IOP %Y DOI: 10.1086/181156 %R 1973ApJ...179..615B %T A Soft X-Ray Survey from the Galactic Center to Cassiopeia %A Burginyon, G.; Hill, R.; Palmieri, T.; Scudder, J.; Seward, F.; Stoering, J.; Toor, A. %J The Astrophysical Journal %V 179 %D 01/1973 %P 615 %L 626 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1973ApJ...179..615B %B Results are presented of a survey of the galactic plane between 1" = 0 and 1" = 145 . The detector was sensitive to X-rays with energy from 0.2 to 18 keV and had an effective area of 640 cm2. Source locations within 0.02 deg2 and spectral parameters have been derived for Cyg 1, Cyg 2, the Cygnus Loop, Ser 1, and the supernova remnant Cas A. Spectral parameters have also been derived for OX 5-i, OX 9+1, OX 13+1, and OX 17+2; however, these sources were located in only one dimension. Some spectral information and locations in one dimension have been obtained for Tycho's supernova remnant, Cyg 3, and seven other sources. Our positions and those measured by the Uhuru satellite are in good agreement. The Cygnus Loop was observed during two nearly perpendicular scans. The data show that the X-ray and radio objects have almost the same spatial extent but different intensity distributions. The northern part of the radio source, the region containing the brightest optical filaments, emits most of the X-ray flux. Subject headings: spectra, X-ray - supernova remnants - X-ray sources %H IOP %Y DOI: 10.1086/151900 %R 1972NucTe..16..571S %T Applications of Low Energy and Gamma Rays %A Seward, Frederick D. %J Nuclear Technology %V 16 %D 12/1972 %P 571 %L 571 %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1972NucTe..16..571S %Y DOI: 10.13182/NT72-A31229 %R 1972ApJ...177..387P %T Observations of Soft X-Rays Two Supernova Remnants in the Constellation Lupus and the Diffuse Background %A Palmieri, T. M.; Burginyon, G. A.; Hill, R. W.; Scudder, J. K.; Seward, F. D. %J The Astrophysical Journal %V 177 %D 11/1972 %P 387 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1972ApJ...177..387P %B X-rays in the energy range 0.6-1.6 keV have been detected from the Lupus Loop and possibly from the remnant of the supernova of 1006 A.D. At lower energies, 0.2-0.6 keY, the sources are not evident, but spatial variations in the diffuse background are such that the flux varies by a factor of 2 within 8 on the sky. %H IOP %Y DOI: 10.1086/151716 %R 1972ApJ...178..131S %T Distances and Absolute Luminosities of Galactic X-Ray Sources %A Seward, F. D.; Burginyon, G. A.; Grader, R. J.; Hill, R. W.; Palmieri, T. M. %J The Astrophysical Journal %V 178 %D 11/1972 %P 131 %L 142 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1972ApJ...178..131S %B Data from two soft X-ray surveys are combined to propose a distance scale for 20 X-ray sources. These are the bright sources that lie close to the galactic plane. A relationship between measured absorption and distance is derived by using supernova remnants with known distances for nearby objects and by requiring a rough symmetry about the galactic center for the distant sources. Based on this distance scale, the calculated absolute luminosities of the sources range from 10 ' to 10 ' ergs 5-'. The sources that have not been identified with supernova remnants tend to fall into two groups. One group has luminosities in excess of 10 ' ergs 5 -`, about the same strength as the sources found in the Magellanic Clouds. These strong sources lie in a loose cluster about the galactic center. A second group of sources have luminosities that average approximately 10 ergs s '. These weaker sources were detectable by our experiment out to a distance of only about 5 kpc from the Sun. The X-ray absorption data require that the relative amount of medium-weight elements in interstellar material be greater than that of the accepted cosmic abundances, or alternatively that the density of these elements increase in the region of the galactic center. %H IOP %Y DOI: 10.1086/151773 %R 1972ApJ...176..611P %T Observation of Several X-Ray Sources in 1970 September %A Price, R. E.; Seward, F. D.; Swift, C. D. %J The Astrophysical Journal %V 176 %D 09/1972 %P 611 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I NED: NASA/IPAC Extragalactic Database; %U https://ui.adsabs.harvard.edu/abs/1972ApJ...176..611P %B Several X-ray sources were detected in a survey of the sky on 1970 September 24. Intensities were measured for Tau XR-1, Cyg XR-1, Cyg XR-2, NGC 1275, Cas A, Cyg XR-3, 2U 0613+9, 2U 1908+0, and 2U 1912-5. Locations are reported for the latter four sources, which are thus far unidentified with optical or radio objects. %H IOP %Y DOI: 10.1086/151662 %R 1972ITAES...8..407S %T The Role of Modern Sensor Applications in the United Nations Resource Exploration and Evaluation Programs %A Seward, Franklin %J IEEE Transactions on Aerospace Electronic Systems %V 8 %D 07/1972 %P 407 %L 409 %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1972ITAES...8..407S %H IEEE %Y DOI: 10.1109/TAES.1972.309537 %R 1972BAAS....4..219P %T Observations of Soft X-Rays: Two Supernova Remnants in the Constellation Lupus and the Diffuse Background. %A Palmieri, T. M.; Burginyon, G.; Hill, R.; Seward, F. %J Bulletin of the American Astronomical Society %V 4 %D 03/1972 %P 219 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1972BAAS....4..219P %R 1972ApJ...172L..73T %T Limit on Line Emission in the Diffuse X-Ray Background. %A Toor, A.; Price, R. E.; Seward, F. D. %J The Astrophysical Journal %V 172 %D 03/1972 %P L73 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1972ApJ...172L..73T %B Diffuse X-ray background data from an extended region in the galactic plane and near the South Galactic Pole do not exhibit an enhancement in the spectrum near 7 keV. %H IOP %Y DOI: 10.1086/180894 %R 1972BAAS....4..221S %T Distance &Absolute Luminosities of Galactic X-Ray Sources. %A Seward, F. D.; Burginyon, G.; Grader, R.; Hill, R.; Palmieri, T.; Stoering, J. %J Bulletin of the American Astronomical Society %V 4 %D 03/1972 %P 221 %I CITATIONS: Citations to the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1972BAAS....4..221S %R 1972ApJ...171..519H %T A Soft X-Ray Survey from the Galactic Center to VELA %A Hill, R. W.; Burginyon, G.; Grader, R. J.; Palmieri, T. M.; Seward, F. D.; Stoering, J. P. %J The Astrophysical Journal %V 171 %D 02/1972 %P 519 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1972ApJ...171..519H %B A 640 Cm2 proportional-counter system, sensitive from 0.2 to 12 keV, was used to survey the galactic plane from Sagittarius to Vela. Spatial resolution was 1 , at best. The soft X-ray sky is dominated by a region of strong emissi9n in the vicinity of Vela X and has an appearance quite different from the sky viewed at photon energies of a few kilovolts. Many sources were located in one dimension in the direction of the galactic center. Some of these positions agree well with those of previous experiments. Locations were derived for two strong sources; GX 292+0 or Cen 3, and GX 322+0 or Cir 1. Positions are restricted to a region with area less than 0 2 square degrees. Another weaker source, GX 296-2 or Cen 5, was located in a region of area 0.6 square degrees. A definite source of soft X-rays, which seems to coincide with the objectn Car, was seen. The source Nor 1 was found to emit a greater flux of soft X-rays than other surrounding objects relative to its overall strength. Spectra are derived for all sources, and numbers are given for interstellar material in the line of sight. %H IOP %Y DOI: 10.1086/151305 %R 1971ApJ...169..515S %T X-Rays from Puppis A and the Vicinity of Vela X %A Seward, F. D.; Burginyon, G. A.; Grader, R. J.; Hill, R. W.; Palmieri, T. M.; Stoering, J. P. %J The Astrophysical Journal %V 169 %D 11/1971 %P 515 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1971ApJ...169..515S %B A new rocket observation of the Vela region confirms that Vel X and Pup A are strong sources of soft X-rays. X-rays from Vel X come from a broad region of sky with a diameter of 5 . This region is centered neither on the Vel X radio source nor on the pulsar. Optical filaments lie along one edge of the X-ray emitting region. X-ray spectra are derived for Vel X and Pup A. Neither source was detectable above 2 keV. %H IOP %Y DOI: 10.1086/151168 %R 1971ApJ...169...33P %T Diffuse Cosmic X-Ray Flux from 0.2 to 2 keV %A Palmieri, T. M.; Burginyon, G. A.; Grader, R. J.; Hill, R. W.; Seward, F. D.; Stoering, J. P. %J The Astrophysical Journal %V 169 %D 10/1971 %P 33 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1971ApJ...169...33P %B Observations of the low-energy diffuse X-ray background have been made with a new detector system sensitive in the range from 0.2 to 2 keV. An electrostatic rejection system was used to eliminate electrons as a source of non-X-ray background. The spectrum above 2 keV agrees with that reported by other authors. Between 0.2 and 1.5 keV a good fit to the spectrum is given by JAT/dE E-' exp (-E/O.45) photons (cm S keV sterad)-'. The spatial distribution of the flux below 1 keV is complicated. Possible interpretations are discussed. The flux at 0.25 keV is basically in agreement with that obtained by other authors. In the region of sky covered by this observation, the variation of flux with galactic latitude implies a galactic origin for most of the diffuse soft X-rays. %H IOP %Y DOI: 10.1086/151115 %R 1971ApJ...168L..15T %T X-Ray Source Positions for Cygnus X-1, Cygnus X-2, and Cygnus X-3 %A Toor, A.; Price, R.; Seward, F.; Scudder, J. %J The Astrophysical Journal %V 168 %D 08/1971 %P L15 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1971ApJ...168L..15T %B On 1970 September 24, the Cygnus region was scanned with a large scintillation counter. From the analysis of the data between 5 and 35 keV, we report source locations for Cyg x-1, Cyg X-2, and Cyg X-3. The locations for Cyg X-2 and Cyg X-3 are in agreement with previous experiments. The center of the 20 arc min2 error box for Cyg X-1 is displaced by about 9' from the recently published Uhuru data. %H IOP %Y DOI: 10.1086/180775 %R 1971ApJ...168L...7P %T X-Rays from the Magellanic Clouds %A Price, R. E.; Groves, D. J.; Rodrigues, R. M.; Seward, F. D.; Swift, C. D.; Toor, A. %J The Astrophysical Journal %V 168 %D 08/1971 %P L7 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %U https://ui.adsabs.harvard.edu/abs/1971ApJ...168L...7P %B X-rays from the vicinities of both Magellanic Clouds were observed with a spatial resolution of 10 on 1970 September 24. Each Cloud appears as an extended source. The center of X-ray emission is displaced from the region of maximum optical emission. The X-ray spectrum of the Large Cloud is much softer than that of the Small Cloud. The data are more easily interpreted as due to a few strong sources rather than many unresolved weak sources. It is possible that the 30 Doradus nebula is one of these strong sources. %H IOP %Y DOI: 10.1086/180773 %R 1971BAAS....3Q.393S %T Soft X-Rays from Vela-X and Puppis A. %A Seward, F. D.; Burginyon, G. A.; Grader, R. J.; Hill, R. W.; Palmieri, T. M. %J Bulletin of the American Astronomical Society %V 3 %D 06/1971 %P 393 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1971BAAS....3Q.393S %R 1971ApJ...164...61P %T Soft X-Rays from Two Supernova Remnants %A Palmieri, T. M.; Burginyon, G.; Grader, R. J.; Hill, R. W.; Seward, F. D.; Stoering, J. P. %J The Astrophysical Journal %V 164 %D 02/1971 %P 61 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1971ApJ...164...61P %B During a controlled scan with a low-energy X-ray detector, a region of X-ray emission was located coincident with the Vela-Puppis complex of radio sources. The supernova remnant Pup A is observed as an isolated source. The Vel X region is extended, with some evidence for structure. %H IOP %Y DOI: 10.1086/150815 %R 1971BAAS....3R..20B %T A Measurement of the Diffuse Cosmic X-Ray Flux from 200 eV-10 keV %A Burginyon, G. A.; Grader, R. J.; Hill, R. W.; Stoering, J. P.; Palmieri, T. M.; Seward, F. D. %J Bulletin of the American Astronomical Society %V 3 %D 01/1971 %P 20 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1971BAAS....3R..20B %R 1971BAAS....3R..21H %T X-Ray Source Survey in the Southern Milky Way %A Hill, R. W.; Burginyon, G. A.; Grader, R. J.; Stoering, J. P.; Palmieri, T. M.; Seward, F. D. %J Bulletin of the American Astronomical Society %V 3 %D 01/1971 %P 21 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1971BAAS....3R..21H %R 1971BAAS....3R..22P %T An X-ray Survey with Large-Area Proportional Counters %A Price, R. E.; Groves, D.; Rodrigues, R. M.; Seward, F. D. %J Bulletin of the American Astronomical Society %V 3 %D 01/1971 %P 22 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1971BAAS....3R..22P %R 1971BAAS....3...22S %T A Large-Area X-Ray Survey %A Seward, F. D.; Burginyon, G. A.; Grader, R. J.; Groves, D.; Hill, R. W.; Koppel, L. N.; Palmieri, T. M.; Price, R.; Scudder, J. K.; Stoering, J. P.; Swift, C.; Toor, A. %J Bulletin of the American Astronomical Society %V 3 %D 01/1971 %P 22 %I CITATIONS: Citations to the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1971BAAS....3...22S %R 1970ApJ...161..979M %T Observation of Galactic X-Ray Sources 1968 November 3 %A MacGregor, A.; Seward, F.; Turiel, I. %J The Astrophysical Journal %V 161 %D 09/1970 %P 979 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1970ApJ...161..979M %B The galactic plane was scanned with a large-area proportional counter that was collimated to 20.5 full width at half-maximum transmission in azimuth. The following X-ray sources were seen clearly above the background in the energy range 1-10 keV: Tau XR-1, Sco XR-1, Sco XR-2, Cen XR-3, Nor XR-2/ Lup XR-1, Cyg XR-1, Cyg XR-3, Ser XR-1, and Ser XR-2. The X-ray spectra of these sources have been measured and are given in the energy range 2-10 keV. The variable source Cen XR-2 was not observed, although the location of this source was scanned. During this observation its intensity was less than one-tenth the intensity of Tau XR-1. %H IOP %Y DOI: 10.1086/150598 %R 1970ApJ...161..987B %T Scorpius XR-1: Some X-Ray and Optical Observations (1969 May) %A Burginyon, G. A.; Grader, R. J.; Hill, R. W.; Price, R. E.; Rodrigues, R.; Seward, F. D.; Swift, C. D.; Hiltner, W. A.; Mannery, E. J. %J The Astrophysical Journal %V 161 %D 09/1970 %P 987 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1970ApJ...161..987B %B X-rays from Sco XR-1 were observed 1969 May 17 and 24. Simultaneous optical observations were carried out at Kitt Peak National Observatory. Data from these two dates are plotted and compared with ten previous rocket observations of Sco XR-1. Optical data were obtained simultaneously during six of these earlier flights. These observations are used to search for a correlation between the varying X-ray and varying optical emission of this object. %H IOP %Y DOI: 10.1086/150599 %R 1970ApJ...160.1193G %T Erratum: the Soft X-Ray Spectra of Three Cosmic Sources and Simultaneous Optical Observations of SCO X-1 %A Grader, R. J.; Hill, R. W.; Seward, F. D.; Hiltner, W. A. %J The Astrophysical Journal %V 160 %D 06/1970 %P 1193 %I CITATIONS: Citations to the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1970ApJ...160.1193G %H IOP %Y DOI: 10.1086/150507 %R 1970ApJ...160..209T %T A Measurement of the Optical and X-Ray Emission from Scorpius X-1 and the X-Ray Diffuse Background %A Toor, A.; Seward, F. D.; Cathey, L. R.; Kunkel, W. E. %J The Astrophysical Journal %V 160 %D 04/1970 %P 209 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1970ApJ...160..209T %B Another simultaneous measurement of the optical and X-ray emission from Sco X-1 has been made. A rocket-borne scintillation counter was used to measure the X-ray spectrum from 4 to 40 keV. The optical intensity at the time of the X-ray measurements was B = 12.97 mag. The X-ray spectrum looks like thin-source thermal bremsstrahlung with an apparent plasma temperature of 7 + 1 keV. These data are compared with previous measurements of X-ray and optical emission. It is possible that total energy emission from Sco X-1 follows the B-magnitude in a nearly linear fashion. The diffuse X-ray background was measured in the energy range 4-70 keV. A shutter arrangement made it possible to correct accurately for the cosmic-ray contribution to the background. This measurement agrees with the previously reported spectrum. %H IOP %Y DOI: 10.1086/150418 %R 1970BAAS....2Q.222T %T Observation of Galactic X-Ray Sources on November 3, 1968 %A Turiel, I.; MacGregor, G. A.; Seward, F. D. %J Bulletin of the American Astronomical Society %V 2 %D 03/1970 %P 222 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1970BAAS....2Q.222T %R 1970ApJ...159..201G %T The Soft X-Ray Spectra of Three Cosmic Sources and Simultaneous Optical Observations of SCO XR-1 %A Grader, R. J.; Hill, R. W.; Seward, F. D.; Hiltner, W. A. %J The Astrophysical Journal %V 159 %D 01/1970 %P 201 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1970ApJ...159..201G %B New X-ray spectra have been obtained for Sco XR-1, the Crab Nebula, and a low -energy source currently designated Vela XR-2. The range of photon energies covered was 150 eV-10 keV. The Sco XR-1 data are interpreted as thin-source, thermal bremsstrahlung with absorption in cool material, The new data are compared with previous low-energy spectra of Sco XR-1, and this source is shown to be probably variable in the soft X-ray region. The spectrum of the Crab Nebula shows absorption in cool material at low energies. Vela XR-2 is the most intense source of the three at photon energies <0.5 keV. %H IOP %Y DOI: 10.1086/150303 %R 1970JGR....75.7267H %T Soft particle flux above 130 km at midlatitude %A Hill, R. W.; Grader, R. J.; Seward, F. D.; Stoering, J. P. %F AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California), AC(Lawrence Livermore National Laboratory, California), AD(Lawrence Livermore National Laboratory, California) %J Journal of Geophysical Research %V 75 %D 01/1970 %P 7267 %K Solar Physics and Astrophysics: X-ray astronomy, Particles and Fields in the Ionosphere: X rays %C (c) 1970: American Geophysical Union %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1970JGR....75.7267H %B Measurements have been made from latitudes 22°N and 17°N with rocket-borne, thin-window proportional counters of a variable flux of low-energy particles (electron energy greater than 3 kev) approaching the earth from the southern half of the sky. These particles were detected on three separate rocket flights at altitudes above 120 km and at an L value of approximately 1.1. The three measurements differ in intensity but are very similar in spectral shape, with approximately an E^-1 dependence. A typical flux value is 100 particles/cm² kev sec ster at an energy of 4 kev. These particles are of particular importance in low-energy X-ray astronomy experiments where they may be the dominant source of background in certain regions of the sky. %Y DOI: 10.1029/JA075i034p07267 %R 1969ApJ...158L.131M %T Erratum: Further Simultaneous Observations of the Optical and X-Ray Spectra of SCO X-1 %A Mark, Hans; Price, R.; Rodrigues, R.; Seward, F.; Swift, C.; Hiltner, W. %J The Astrophysical Journal %V 158 %D 11/1969 %P L131 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1969ApJ...158L.131M %H IOP %Y DOI: 10.1086/180449 %R 1969BAAS....1R.365T %T A Simultaneous Measurement of the Optical and X-Ray Emission from Sco X-1 %A Toor, A.; Seward, F. D.; Cathy, L. R.; Kunkel, W. E. %J Bulletin of the American Astronomical Society %V 1 %D 09/1969 %P 365 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1969BAAS....1R.365T %R 1969BAAS....1S.361S %T Interstellar Absorption of Crab Nebula X Rays %A Seward, F. D.; Grader, R. J.; Hill, R. W. %J Bulletin of the American Astronomical Society %V 1 %D 09/1969 %P 361 %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1969BAAS....1S.361S %R 1969ApJ...156L..67M %T Further Simultaneous Observations of the Optical and X-Ray Spectra of SCO X-1 %A Mark, Hans; Price, R. E.; Rodrigues, R.; Seward, F. D.; Swift, C. D.; Hiltner, W. A. %J The Astrophysical Journal %V 156 %D 05/1969 %P L67 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1969ApJ...156L..67M %B Simultaneous observations have again been made of the fluctuating optical and X-ray emission from Sco X-1. Previous measurements and a discussion of possible correlation have been published. Two new measurements are reported here in which the optical intensity was relatively faint (B = 13.14 and 13.22 mag). The X-ray intensity was 2.5 X 1O~ and 2.2 X 1O~ erg cm2 sec' between 2 and 20 keV, and the apparent plasma temperatures (KT) were 7 and 5.5 keV. An extrapolation of the X-ray spec- trum was compared with the observed optical spectrum, yielding agreement. Parameters, viz., plasma radius and density and total energy flux, of a model previously proposed are inferred from the present data. It is noted that the total energy flux is greatest when the object is brightest %H IOP %Y DOI: 10.1086/180351 %R 1969ApJ...155L.143M %T Detection of X-Rays from the Large Magellanic Cloud %A Mark, Hans; Price, R.; Rodrigues, R.; Seward, F. D.; Swift, C. D. %J The Astrophysical Journal %V 155 %D 03/1969 %P L143 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %U https://ui.adsabs.harvard.edu/abs/1969ApJ...155L.143M %B A source of low-energy X-ray.s approximately 12° wide has been detected at the position of the Large Magellanic Cloud. Between 1.5 and 10.5 keV the spectrum is slightly softer than that of the isotropic background. The observed flux corresponds to an emission rate of about 4 X 1038 ergs sec' %H IOP %Y DOI: 10.1086/180322 %R 1969S&T....37...79G %T A Search for South X-Rays from the Galaxy %A Grader, R. J.; Hill, R. W.; Seward, F. D. %J Sky and Telescope %V 37 %D 02/1969 %P 79 %I CITATIONS: Citations to the Article; %U https://ui.adsabs.harvard.edu/abs/1969S&T....37...79G %R 1968ApJ...154..655H %T The Soft X-Ray Spectrum of SCO XR-1 %A Hill, R. W.; Grader, R. J.; Seward, F. D. %J The Astrophysical Journal %V 154 %D 11/1968 %P 655 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1968ApJ...154..655H %B The X-ray spectrum of Sco XR-1 has been measured in the energy range from 06 to 9 keV. A change of approximately a factor of 2 in intensity has been noted since the previous measurement in October 1965. The spectra of the diffuse background and of a group of sources near the galactic center were also measured %H IOP %Y DOI: 10.1086/149787 %R 1968JGR....73.7149G %T X-ray airglow in the daytime sky %A Grader, R. J.; Hill, R. W.; Seward, F. D. %F AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California), AC(Lawrence Livermore National Laboratory, California) %J Journal of Geophysical Research %V 73 %D 11/1968 %P 7149 %L 7153 %K Particles and Fields in the Ionosphere: X rays, Particles and Fields in the Ionosphere: Airglow, Aeronomy: Atmospheric absorption and scattering of radiation (particles or waves) %C Copyright 1968 by the American Geophysical Union. %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1968JGR....73.7149G %Y DOI: 10.1029/JB073i022p07149 %R 1968ApJ...154..645C %T Simultaneous Observations of the Optical and X-Ray Spectra of SCO XR-1 %A Chodil, G.; Mark, Hans; Rodrigues, R.; Seward, F. D.; Swift, C. D.; Turiel, Isaac; Hiltner, W. A.; Wallerstein, George; Mannery, E. J. %J The Astrophysical Journal %V 154 %D 11/1968 %P 645 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1968ApJ...154..645C %B This paper reports the results of two simultaneous optical and X-ray intensity measurements of the cosmic X-ray source Sco XR-1. Rocket-borne proportional counters were used to measure the X-ray spectra from 2 to 20 keV on May 18, 1967, and September 29, 1967 Optical intensities were meas- ured during the rocket flights at the Cerro Tololo Inter-American Observatory in Chile. The X-ray data could be approximated by thermal bremsstrahlung from a hot plasma for both experiments, with a tem- perature of 8.1 X 1O~ ° and 4 6 X 1O~ ° K, respectively, and optical intensities of B = 12 83 and 12.49, respectively. The X-ray spectrum is extrapolated into the optical region and compared with the optical measurements. Agreement can be obtained when self-absorption in the hot plasma and interstellar ex- tinction are considered in extrapolating the X-ray spectrum %H IOP %Y DOI: 10.1086/149786 %R 1968ApJ...152L.135B %T Spectrum of the Central Star in NGC 5189 %A Blanco, V.; Kunkel, W.; Hiltner, W. A.; Chodil, G.; Mark, Hans; Rodrigues, R.; Seward, F.; Swift, C. D. %J The Astrophysical Journal %V 152 %D 06/1968 %P L135 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %I NED: NASA/IPAC Extragalactic Database; %U https://ui.adsabs.harvard.edu/abs/1968ApJ...152L.135B %B The spectrum of the central star in NGC 5189 shows strong, broad emission of 0 vi XX3811 and 3834 and less broad He u X4686 emission. Variability of the star is briefly discussed %H IOP %Y DOI: 10.1086/180197 %R 1968AJS....73R.179G %T Soft x-Rays from a New Source in the Constellation Vela. %A Grader, R. J.; Hill, R. W.; Seward, F. D. %J The Astronomical Journal Supplement %V 73 %D 01/1968 %P 179 %I ABSTRACT: Abstract; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1968AJS....73R.179G %B On 14 May 1968 a rocket-borne proportional counter detected x rays of energies between 200 and 800 eV from a source in the constellation Vela. It is believed that the source is the Woif-Rayet binary ~i Velorum. The count rate increases with decreasing energy, and, below 500 eV the count rate is higher than that of Sco XR-1. The observation described locates the source to within approximately 20 of ~2 Velorum. Until a positive correiation is made, the designation Vela XR-2 is suggested. This work was performed under the auspices of the USAFC. %R 1968AJS....73Q.184H %T Simultaneous Observations of the Optical and x-Ray Spectra of SCO XR-1. %A Hiltner, W. A.; Mark, Hans; Rodrigues, R.; Seward, F. D.; Swift, C. D.; Turiel, Isaac; Chodil, G.; Wallerstein, George; Mannery, E. J. %J The Astronomical Journal Supplement %V 73 %D 01/1968 %P 184 %I ABSTRACT: Abstract; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1968AJS....73Q.184H %B This paper is a report of four simultaneous optical and x-ray intensity measurements of the cosmic x-ray source Sco XR- 1. Rocket-borne proportional counters were used to measure the x-ray flux and the spectrum in the energy region between 2 and 20 keV. The counters had thin beryllium windows and were filled with a xenon- methane (90%-10%) mixture. An annular anti- coincidence system was used to suppress the background caused by energetic charged particles. The optical intensities of Sco XR- 1 during the rocket flights were measured at the Cerro Tololo Inter- American Observatory in Chile. The flights were carried out on 18 May 1967, 29 September 1967, 9 May 1968, and 19 May 1968 (UT). Within the precision of the present measurements, the x-ray spectra observed in all investigations can be approximated by thermal bremsstrahlung from a hot plasma. The quantitative results are shown in Table I. The x-ray spectrum calculated for a "thin" plasma can be extrapolated into the optical region. TABLE I. x-ray intensity (ergs/cm2 per sec between Temperature B Flight 2-20 keV) (~K) magnitude 18May1967 2.9X107 8.1X107 12.83 29 Sept. 1967 3.6X10-7 4.6X107 12.49 9May1968 2.5X107 8.1X107 13.17 19May1968 2.2X107 6.9X107 13.25 The predicted optical magnitude can be compared with the observed value. The results are found to be inconsistent with the assumption of an optically thin plasma. However, when self-absorption in the optical region is included in the calculation, it is found that the observed visible intensity is correctly predicted from the extrapolation of the bremsstrahlung spectrum. This work was performed under the auspices of the U. S. Atomic Energy Commission. %R 1967ApJ...150..845S %T Diffuse Cosmic X-Ray Background Between 4 and 40 KEV %A Seward, F.; Chodil, G.; Mark, Hans; Swift, C.; Toor, A. %J The Astrophysical Journal %V 150 %D 12/1967 %P 845 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %U https://ui.adsabs.harvard.edu/abs/1967ApJ...150..845S %B Diffuse X-ray background fluxes have been observed in many of the rocket flights made to study discrete X-ray sources. The X-ray background spectrum observed in two recent (September 20 and September 22, 1966) flights from Johnston Island is presented. Observations were made of backgrounds perpendicular to and in the galactic plane. The X-ray flux was found to be roughly isotropic. It follows a power law spectrum having N(E) 1 6 The total radiated energy observed between 4 and 40 keV is 9 X 10-8 ergs sterad-1. %H IOP %Y DOI: 10.1086/149387 %R 1967ApJ...150..405S %T Search for 8-80 KEV X-Rays from the Large Magellanic Cloud and the Crab Nebula %A Seward, F. D.; Toor, A. %J The Astrophysical Journal %V 150 %D 11/1967 %P 405 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I NED: NASA/IPAC Extragalactic Database; %U https://ui.adsabs.harvard.edu/abs/1967ApJ...150..405S %B An X-ray detector was flown on a sounding rocket launched from Johnston Atoll. The region scanned included that part of the south circumpolar sky containing the Large Magellanic Cloud. No X-rays were detectable above background from the direction of the Large Magellanic Cloud. An upper limit of 8 X 1 ergs is derived for the X-ray flux between 8- and 60-keV photon energy. X-rays were detected from the Sun and from the Crab Nebula. A spectrum is derived for photons between 10 and 40 keV from the Crab Nebula. The flux in this region is about the same as that measured in a previous experiment. %H IOP %Y DOI: 10.1086/149343 %R 1967ApJ...150...57C %T X-Ray Intensities and Spectra from Several Cosmic Sources %A Chodil, G.; Mark, Hans; Rodrigues, R.; Seward, F. D.; Swift, C. D. %J The Astrophysical Journal %V 150 %D 10/1967 %P 57 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I ADS_SCAN: Scanned Article (GIF); %I ADS_PDF: ADS PDF; %I SIMBAD: SIMBAD Database at the CDS; %U https://ui.adsabs.harvard.edu/abs/1967ApJ...150...57C %B This paper reports the results of X-ray spectrum and intensity measurements for several cosmic X-ray sources. Two flights were conducted, one from Kauai, Hawaii on July 28, 1966, and the other from Johnston Atoll on September 20,1966. Proportional counters with anticoincidence shields to eliminate charged-particle background counts were used to detect the X-rays. Four known sources were observed: Sco XR-1, Tau XR-1, Cyg XR-1, and Cyg XR-2. Total intensity determinations were made for all of these sources, and spectra were obtained for Sco XR-1 and Cyg XR-2. A search was made for X-rays from the Large and Small Magellanic Clouds, but no X-rays above background were found in that region of the sky. An upper limit of the X-ray intensity from the Magellanic Clouds has been determined from these data. A weak X-ray source not previously observed was found in the constellation Vela (Vel XR-1). %H IOP %Y DOI: 10.1086/149312 %R 1967PhRvL..19..681C %T Spectral and Location Measurements of Several Cosmic X-Ray Sources Including a Variable Source in Centaurus %A Chodil, G.; Mark, Hans; Rodrigues, R.; Seward, F.; Swift, C. D.; Hiltner, W. A.; Wallerstein, George; Mannery, Edward J. %F AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California), AC(Lawrence Livermore National Laboratory, California), AD(Lawrence Livermore National Laboratory, California), AE(Lawrence Livermore National Laboratory, California), AF(University of Chicago), AG(University of Washington, Seattle), AH(University of Washington, Seattle) %J Physical Review Letters %V 19 %D 09/1967 %P 681 %L 683 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1967PhRvL..19..681C %B This paper reports the results of x-ray spectrum and location measurements of several cosmic x-ray sources made on 18 May 1967. Rocket-borne proportional counters were used. The x-ray spectra of Sco XR-1, Tau XR-1, and Lup XR-1 were measured, and the location of Vel XR-1, Lup XR-1, and a new source Cen XR-3 were determined. In addition, the x-ray spectrum and location of a variable source, Cen XR-2, were obtained. %H APS %Y DOI: 10.1103/PhysRevLett.19.681 %R 1966Sci...152.1499G %T X-Ray Spectra from Three Cosmic Sources %A Grader, R. J.; Hill, R. W.; Seward, F. D.; Toor, A. %J Science %V 152 %D 06/1966 %P 1499 %L 1504 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1966Sci...152.1499G %B Three cosmic x-ray sources have been observed from a water-launched rocket carrying two x-ray detectors to an altitude of 200 kilometers. The x-ray spectra, measured in the photon energy range between 1 and 40 kiloelectron volts, are all different. The sources in order of hardness of spectra are Cyg XR-1, Tau XR-1, and Sco XR-1. The intensity of Sco XR-1 decreased at low photon energies. The differences in spectra might be interpreted as evidence of different source mechanisms. %Y DOI: 10.1126/science.152.3728.1499 %R 1965PhRvL..15..605C %T X-Ray Spectra from Scorpius (SCO-XR-1) and the Sun Observed Above the Atmosphere %A Chodil, G.; Jopson, R. C.; Mark, Hans; Seward, F. D.; Swift, C. D. %F AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California), AC(Lawrence Livermore National Laboratory, California), AD(Lawrence Livermore National Laboratory, California), AE(Lawrence Livermore National Laboratory, California) %J Physical Review Letters %V 15 %D 10/1965 %P 605 %L 607 %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I Co-Reads: Co-Reads; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1965PhRvL..15..605C %H APS %Y DOI: 10.1103/PhysRevLett.15.605 %R 1965JGR....70.3557S %T Near-Earth, Polar-Orbiting Satellite Measurements of Charged Particles 1, Instrumentation and Cosmic Rays %A Seward, F. D.; Kornblum, H. N., Jr. %J Journal of Geophysical Research %V 70 %D 08/1965 %P 3557 %L 3570 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1965JGR....70.3557S %B A set of scintillation counters was carried on polar-orbiting Air Force satellites in the last half of 1961. Cosmic-ray effects were observed at high latitudes with good statistics. The L value of the `edge' of the cosmic-ray plateau was found to vary with longitude and to vary between L = 2.7 and L = 3.3. This corresponds to a `knee' at from L = 3.1 to L = 3.7. A`kneecap,' consistently observed at the plateau edge, is interpreted as the appearance of reentrant albedo as the satellite moves to lower latitudes. The relative amount of this albedo was 8±2% at an altitude of 300 km. A day-night effect in the observed high-latitude reentrant albedo cutoff is consistent with known day-night changes in the magnetosphere. The observed altitude dependence of flux at very high latitudes is used to derive an omnidirectional interplanetary flux of 2.6±0.3 particles/cm² sec at this time. %Y DOI: 10.1029/JZ070i015p03557 %R 1963spre.conf..477H %T Electron Loss Rate from the Outer Radiation Belt %A Hess, W. N.; Bloom, S. D.; Mann, L. G.; Seward, F. D.; West, H. I., Jr. %F AA(NASA Goddard Space Flight Center, Maryland), AB(Lawrence Livermore National Laboratory, California), AC(Lawrence Livermore National Laboratory, California), AD(Lawrence Livermore National Laboratory, California), AE(Lawrence Livermore National Laboratory, California) %J Space Research Conference %D 01/1963 %P 477 %I CITATIONS: Citations to the Article; %U https://ui.adsabs.harvard.edu/abs/1963spre.conf..477H %R 1962PhRv..125..335S %T Resonant Scattering of Gamma Rays from Nuclear Levels with a Linear Accelerator %A Seward, F. D. %F AA(Lawrence Livermore National Laboratory, California) %J Physical Review %V 125 %D 01/1962 %P 335 %L 340 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1962PhRv..125..335S %B Several elements have been irradiated with a high-intensity bremsstrahlung beam and a search has been made for γ rays scattered from nuclear levels. A 6-in.×5-in.-diameter NaI(Tl) crystal was used as the detector. Resonant scattering was seen from Li⁶, B¹¹, C¹², O¹⁶, Mg, and Si. Pulse-height spectra for γ rays scattered from each of these are shown. Application of these spectra to previous experiments in which level widths and branching ratios were calculated is discussed. Levels in B¹¹, C¹², and O¹⁶ were observed which have not been seen with this technique previously. %H APS %Y DOI: 10.1103/PhysRev.125.335 %R 1961PhRv..121..605S %T Measurement of the Annihilation-in-Flight Cross Section at 0° for 8.5-Mev Positrons %A Seward, F. D.; Hatcher, C. R.; Fultz, S. C. %F AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California), AC(Lawrence Livermore National Laboratory, California) %J Physical Review %V 121 %D 01/1961 %P 605 %L 609 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1961PhRv..121..605S %B The differential cross section at 0° for the annihilation in flight of 8.5-Mev positrons has been measured. The positrons were created in a thick Ta target which was bombarded by 20-Mev electrons from a linear accelerator. They were directed onto a Be target where annihilation occurred, and the annihilation photons were measured by use of a thick-crystal spectrometer. The measured value for the cross section is 1.3+/-0.2 barns/steradian per electron, which is in agreement with theory. %H APS %Y DOI: 10.1103/PhysRev.121.605 %R 1959PhRv..114..514S %T Reaction Mechanism in Inelastic Scattering of Protons from Mg, Cr, and Other Elements from 3.5 to 7 Mev %A Seward, Frederick D. %F AA(University of Rochester, New York) %J Physical Review %V 114 %D 04/1959 %P 514 %L 525 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1959PhRv..114..514S %B Inelastic scattering of protons leading to the first excited states of Mg²⁴ and Cr⁵² and to single excited states of other elements has been studied. dσdω (90°) was measured as a function of proton energy from 3.5 to 7 Mev. Angular distributions of inelastically scattered protons and p'-γ angular correlations were taken at several energies. Experimental measurements are compared with direct-interaction theory and with predictions of the statistical model. Data for Cr⁵²(p, p')Cr^52* at 5.4 Mev is well fit by the statistical model. The Mg²⁴(p, p')Mg^24* reaction at 7 Mev can be interpreted as a direct interaction. The Mg reaction at 5.4 Mev and the Cr reaction at 7 Mev appear to have a bit of direct interaction in them. It is suggested that the amount of direct interaction in this (p, p') reaction depends on the nuclear barrier height. Statistical-model expressions for reactions studied are given in an Appendix. %H APS %Y DOI: 10.1103/PhysRev.114.514 %R 1959PhDT........22S %T Inelastic Scattering of Protons by Magnesium, Chromium, and Other Elements from 3.5 to 7 Mev. %A Seward, Frederick Downing %F AA(University of Rochester, New York) %J Ph.D. Thesis %D 01/1959 %K Physics: Nuclear %U https://ui.adsabs.harvard.edu/abs/1959PhDT........22S %R 1957PhRv..107..159S %T Reaction F¹⁹(d, p)F²⁰ and the Spin of F²⁰ %A Seward, F. D.; Slaus, I.; Fulbright, H. W. %F AA(University of Rochester, New York), AB(University of Rochester, New York), AC(University of Rochester, New York) %J Physical Review %V 107 %D 07/1957 %P 159 %L 160 %I ABSTRACT: Abstract; %I CITATIONS: Citations to the Article; %I REFERENCES: References in the Article; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1957PhRv..107..159S %B New measurements of the angular distribution of the protons from the reaction F¹⁹(d, p)F²⁰ made with deuterons in the range 3.5<=E_d<=4.1 Mev show that the reaction proceeds mainly by compound-nucleus formation, and that stripping makes at most a small contribution. It follows that the interpretation of the results of an earlier experiment in terms of stripping is unjustified, hence that the spin of F²⁰ is not necessarily 1. At all energies the angular distribution of protons leaving F²⁰ in its first excited state shows a clear stripping curve corresponding to l_n=2. %H APS %Y DOI: 10.1103/PhysRev.107.159 %R 1935RSPSB.118..197R %T Discussion on the Origin and Relationship of the British Flora %A Seward; Reid, E. M.; Boswell, P. G. H.; Chandler, M. E. J.; Godwin, H.; Wilmott, A. J.; Salisbury, E. J.; Raistrick, A.; Du Rietz, G. Einar; Watson, W.; Simpson, G. C.; Dewey; Simpson, J. B.; Sandford, K. S.; Butcher, R. W.; Wright, W. B.; Hamshaw Thomas, H.; Burkitt, Miles; Burtt Davy, J.; Turrill, W. B.; Watt, Alex S.; Hollingworth %J Proceedings of the Royal Society of London Series B %V 118 %D 08/1935 %P 197 %L 241 %I CITATIONS: Citations to the Article; %I PUB_HTML: Publisher Article; %U https://ui.adsabs.harvard.edu/abs/1935RSPSB.118..197R %Y DOI: 10.1098/rspb.1935.0054