TY - CONF TI - Chandra Observation of the Large Magellanic Cloud Supernova Remnant J0550-6823 AU - Seward, Frederick AD - AA(Harvard Smithsonian Center for Astrophysics) JO - AAS/High Energy Astrophysics Division VL - 20 Y1 - 2023/09/1 SP - 116.115 UR - https://ui.adsabs.harvard.edu/abs/2023HEAD...2016115S N2 - 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. ER - TY - JOUR TI - The Large Magellanic Cloud Supernova Remnant MCSNR J0550-6823 AU - Seward, Frederick D. AU - Points, Sean D. AD - AA(Smithsonian Astrophysical Observatory), AB(Cerro Tololo Interamerican Observatory) JO - The Astrophysical Journal VL - 950 Y1 - 2023/06/1 SP - 74 KW - X-ray astronomy KW - Large Magellanic Cloud KW - Type II supernovae KW - Supernova remnants KW - 1810 KW - 903 KW - 1731 KW - 1667 UR - https://ui.adsabs.harvard.edu/abs/2023ApJ...950...74S N2 - 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. PB - IOP DO - 10.3847/1538-4357/acc656 SN - 0004-637X ER - TY - JOUR TI - XMM Observation of the Supernova Remnant J0454-6713 and the Adjacent N9 Superbubble AU - Seward, Frederick D. AU - Foster, Adam R. AU - Smith, Randall K. AU - Points, Sean D. AD - AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory), AC(Smithsonian Astrophysical Observatory), AD(Cerro Tololo Interamerican Observatory) JO - The Astrophysical Journal VL - 909 Y1 - 2021/03/1 SP - 13 KW - Supernova remnants KW - Large Magellanic Cloud KW - X-ray astronomy KW - Plasma astrophysics KW - Type Ia supernovae KW - 1667 KW - 903 KW - 1810 KW - 1261 KW - 1728 UR - https://ui.adsabs.harvard.edu/abs/2021ApJ...909...13S N2 - 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. PB - IOP DO - 10.3847/1538-4357/abd561 SN - 0004-637X ER - TY - JOUR TI - J0453-6655, the Supernova Remnant in N4D AU - Seward, F. D. AU - Smith, R. K. AU - Slane, P. O. AU - Murray, S. S. AU - Points, S. D. AU - Gordon, A. J. R. AU - Dickel, J. R. AD - 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) JO - The Astrophysical Journal VL - 861 Y1 - 2018/07/1 SP - 154 KW - H ii regions KW - ISM: supernova remnants KW - Magellanic Clouds UR - https://ui.adsabs.harvard.edu/abs/2018ApJ...861..154S N2 - 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. PB - IOP DO - 10.3847/1538-4357/aabf43 SN - 0004-637X ER - TY - MISC TI - The Spectrum of the Magellanic Cloud Supernova Remnant 0454-67.2 in N9 AU - Seward, Frederick JO - XMM-Newton Proposal Y1 - 2015/10/1 SP - 67 UR - https://ui.adsabs.harvard.edu/abs/2015xmm..prop...67S N2 - 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. ER - TY - CONF TI - Where are the Low-mass Neutron Stars? AU - Seward, Frederick AD - AA(Smithsonian Astrophysical Observatory) JO - 15 Years of Science with Chandra Y1 - 2014/11/1 SP - P58 UR - https://ui.adsabs.harvard.edu/abs/2014fysc.confP..58S N2 - 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. ER - TY - JOUR TI - Azimuthal Structure of the Cyg X-2 X-Ray Dust Halo AU - Seward, F. D. AU - Smith, R. K. AD - AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory) JO - The Astrophysical Journal VL - 769 Y1 - 2013/05/1 SP - 17 KW - dust KW - extinction KW - X-rays: individual: Cyg X-2 UR - https://ui.adsabs.harvard.edu/abs/2013ApJ...769...17S N2 - 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. PB - IOP DO - 10.1088/0004-637X/769/1/17 SN - 0004-637X ER - TY - CONF TI - X-ray Astronomy at Lawrence Livermore Laboratory 1965-1975 AU - Seward, Frederick D. AD - AA(Harvard Smithsonian Center for Astrophysics) JO - American Astronomical Society Meeting Abstracts #221 VL - 221 Y1 - 2013/01/1 SP - 113.12 UR - https://ui.adsabs.harvard.edu/abs/2013AAS...22111312S N2 - 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. ER - TY - JOUR TI - DEM L241, a Supernova Remnant Containing a High-mass X-Ray Binary AU - Seward, F. D. AU - Charles, P. A. AU - Foster, D. L. AU - Dickel, J. R. AU - Romero, P. S. AU - Edwards, Z. I. AU - Perry, M. AU - Williams, R. M. AD - 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) JO - The Astrophysical Journal VL - 759 Y1 - 2012/11/1 SP - 123 KW - ISM: supernova remnants KW - Magellanic Clouds KW - X-rays: binaries KW - X-rays: individual: DEM L241 KW - Astrophysics - High Energy Astrophysical Phenomena UR - https://ui.adsabs.harvard.edu/abs/2012ApJ...759..123S N2 - 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 _⊙ PB - IOP DO - 10.1088/0004-637X/759/2/123 C1 - eprint: arXiv:1208.1453 SN - 0004-637X ER - TY - CONF TI - The X-ray Structure Of The Supernova Remnant And Pulsar-wind Nebula in DEM L 241 AU - Murphy Williams, Rosa Nina AU - Seward, F. AU - Dickel, J. AU - Edwards, Z. AU - Furnish, B. AU - Perry, M. AU - Williams, T. AD - 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) JO - American Astronomical Society Meeting Abstracts #219 VL - 219 Y1 - 2012/01/1 SP - 239.17 UR - https://ui.adsabs.harvard.edu/abs/2012AAS...21923917M N2 - 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. ER - TY - MISC TI - The Pulsar Wind Nebula in DEM L241 AU - Seward, Frederick JO - Chandra Proposal Y1 - 2010/09/1 SP - 3135 UR - https://ui.adsabs.harvard.edu/abs/2010cxo..prop.3135S N2 - 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. ER - TY - BOOK TI - Exploring the X-ray Universe AU - Seward, Frederick D. AU - Charles, Philip A. JO - Exploring the X-ray Universe by Frederick D. Seward and Philip A. Charles. Cambridge University Press Y1 - 2010/08/1 UR - https://ui.adsabs.harvard.edu/abs/2010exru.book.....S N2 - 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. ER - TY - JOUR TI - A Chandra Observation of SNR 0540 - 697 AU - Seward, F. D. AU - Williams, R. M. AU - Chu, Y. -H. AU - Gruendl, R. A. AU - Dickel, J. R. AD - 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) JO - The Astronomical Journal VL - 140 Y1 - 2010/07/1 SP - 177 EP - 183 KW - dust KW - extinction KW - H II regions KW - ISM: supernova remnants KW - Magellanic Clouds KW - techniques: image processing KW - X-rays: individual: SNR 0540 – 697 UR - https://ui.adsabs.harvard.edu/abs/2010AJ....140..177S N2 - 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. PB - IOP DO - 10.1088/0004-6256/140/1/177 SN - 0004-6256 ER - TY - CONF TI - A Chandra Observation of SNR 0540-697 AU - Seward, Frederick D. AU - Williams, R. AU - Chu, Y. AU - Dickel, J. AU - Gruendl, R. AD - 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) JO - AAS/High Energy Astrophysics Division #11 VL - 11 Y1 - 2010/03/1 SP - 18.05 UR - https://ui.adsabs.harvard.edu/abs/2010HEAD...11.1805S N2 - 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. ER - TY - MISC TI - Chandra Supernova Remnant Catalog Update AU - Seward, Frederick JO - Chandra Proposal Y1 - 2009/09/1 SP - 4168 UR - https://ui.adsabs.harvard.edu/abs/2009cxo..prop.4168S N2 - 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. ER - TY - JOUR TI - The Thermal Composite Supernova Remnant Kesteven 27 as Viewed by Chandra: Shock Reflection from a Cavity Wall AU - Chen, Yang AU - Seward, Frederick D. AU - Sun, Ming AU - Li, Jiang-tao AD - 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) JO - The Astrophysical Journal VL - 676 Y1 - 2008/04/1 SP - 1040 EP - 1049 KW - ISM: individual: Kesteven 27 = G327.4+0.4 KW - radiation mechanisms: thermal KW - shock waves KW - supernova remnants KW - X-rays: ISM KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/2008ApJ...676.1040C N2 - 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. PB - IOP DO - 10.1086/525240 C1 - eprint: arXiv:0711.0515 SN - 0004-637X ER - TY - JOUR TI - X-Ray Timing of PSR J1852+0040 in Kesteven 79: Evidence of Neutron Stars Weakly Magnetized at Birth AU - Halpern, J. P. AU - Gotthelf, E. V. AU - Camilo, F. AU - Seward, F. D. AD - 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) JO - The Astrophysical Journal VL - 665 Y1 - 2007/08/1 SP - 1304 EP - 1310 KW - ISM: Individual: Name: Kesteven 79 KW - ISM: Individual: Alphanumeric: SN 1987A KW - Stars: Pulsars: Individual: Alphanumeric: 1E 1207.4-5209 KW - pulsars: individual (CXOU J185238.6 + 004020) KW - pulsars: individual (PSR J1852 + 0040) KW - Stars: Neutron KW - ISM: Supernova Remnants KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/2007ApJ...665.1304H N2 - 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. PB - IOP DO - 10.1086/519557 C1 - eprint: arXiv:0705.0978 SN - 0004-637X ER - TY - JOUR TI - Faint X-Ray Structure in the Crab Pulsar Wind Nebula AU - Seward, F. D. AU - Tucker, W. H. AU - Fesen, R. A. AD - AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory), AC(Dartmouth College, Department of Physics and Astronomy) JO - The Astrophysical Journal VL - 652 Y1 - 2006/12/1 SP - 1277 EP - 1287 KW - ISM: Individual: Name: Crab Nebula KW - Stars: Neutron KW - ISM: Supernova Remnants KW - X-Rays: ISM KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/2006ApJ...652.1277S N2 - 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. PB - IOP DO - 10.1086/508532 C1 - eprint: arXiv:astro-ph/0608485 SN - 0004-637X ER - TY - MISC TI - Accurate Determination of the Dust-Scattering Halo Around Cyg X-2 AU - Seward, Frederick JO - Chandra Proposal Y1 - 2006/09/1 SP - 2270 KW - Chandra Proposal ID #08910231 UR - https://ui.adsabs.harvard.edu/abs/2006cxo..prop.2270S N2 - 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. ER - TY - JOUR TI - Chandra Observation of the Magellanic Cloud Supernova Remnant 0454-67.2 in N9 AU - Seward, F. D. AU - Williams, R. M. AU - Chu, Y. -H. AU - Dickel, J. R. AU - Smith, R. C. AU - Points, S. D. AD - 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) JO - The Astrophysical Journal VL - 640 Y1 - 2006/03/1 SP - 327 EP - 334 KW - ISM: individual (SNR 0454-67.2) KW - ISM: Supernova Remnants KW - X-Rays: ISM KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/2006ApJ...640..327S N2 - 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. PB - IOP DO - 10.1086/499767 C1 - eprint: arXiv:astro-ph/0511619 SN - 0004-637X ER - TY - JOUR TI - Chandra Observations of the X-Ray Halo around the Crab Nebula AU - Seward, F. D. AU - Gorenstein, P. AU - Smith, R. K. AD - AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory), AC(NASA Goddard Space Flight Center, Maryland; Johns Hopkins University, Department of Physics and Astronomy) JO - The Astrophysical Journal VL - 636 Y1 - 2006/01/1 SP - 873 EP - 880 KW - ISM: Individual: Name: Crab Nebula KW - ISM: Supernova Remnants KW - X-Rays: ISM KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/2006ApJ...636..873S N2 - 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. PB - IOP DO - 10.1086/498105 C1 - eprint: arXiv:astro-ph/0509636 SN - 0004-637X ER - TY - CONF TI - New High Resolution X-ray Studies of Magellanic Cloud Supernova Remnants AU - Williams, R. N. M. AU - Chu, Y. -H. AU - Chen, C. -H. AU - Gruendl, R. A. AU - Dickel, J. R. AU - Seward, F. D. AU - Guerrero, M. A. AU - Shelton, R. AU - MCELS Collaboration JO - The X-ray Universe 2005 VL - 604 Y1 - 2006/01/1 SP - 375 UR - https://ui.adsabs.harvard.edu/abs/2006ESASP.604..375W SN - 1609-042X ER - TY - CONF TI - Chandra spectroscopy of thermal composite supernova remnant Kes 27 AU - Chen, Yang AU - Seward, F. D. AU - Sun, Ming AU - Li, J. -T. JO - 36th COSPAR Scientific Assembly VL - 36 Y1 - 2006/01/1 SP - 3449 UR - https://ui.adsabs.harvard.edu/abs/2006cosp...36.3449C N2 - 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 ER - TY - JOUR TI - Chandra Observations of the W51C Supernova Remnant AU - Koo, Bon-Chul AU - Lee, Jae-Joon AU - Seward, Frederick D. AU - Moon, Dae-Sik AD - 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) JO - The Astrophysical Journal VL - 633 Y1 - 2005/11/1 SP - 946 EP - 952 KW - ISM: Individual: Alphanumeric: W51 KW - ISM: Supernova Remnants KW - X-Rays: ISM UR - https://ui.adsabs.harvard.edu/abs/2005ApJ...633..946K N2 - 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. PB - IOP DO - 10.1086/491468 SN - 0004-637X ER - TY - JOUR TI - Chandra Observations of Open Cluster h Per AU - Evans, N. R. AU - Wolk, S. AU - Bizunok, N. AU - Spitzbart, B. AU - Seward, F. AU - Kenyon, S. AU - Barnes, T. AU - Pasachoff, J. M. JO - Journal of the Royal Astronomical Society of Canada VL - 99 Y1 - 2005/08/1 SP - 136 UR - https://ui.adsabs.harvard.edu/abs/2005JRASC..99R.136E N2 - 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. SN - 0035-872X ER - TY - JOUR TI - Supernova Remnants in the Magellanic Clouds. V. The Complex Interior Structure of the N206 Supernova Remnant AU - Williams, R. M. AU - Chu, Y. -H. AU - Dickel, J. R. AU - Gruendl, R. A. AU - Seward, F. D. AU - Guerrero, M. A. AU - Hobbs, G. AD - 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) JO - The Astrophysical Journal VL - 628 Y1 - 2005/08/1 SP - 704 EP - 720 KW - ISM: Individual: Alphanumeric: SNR B0532-71.0 KW - Galaxies: Magellanic Clouds KW - X-Rays: ISM KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/2005ApJ...628..704W N2 - 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. PB - IOP DO - 10.1086/431349 C1 - eprint: arXiv:astro-ph/0504609 SN - 0004-637X ER - TY - JOUR TI - Chandra observations of open cluster h Per. AU - Evans, N. R. AU - Wolk, S. AU - Bizunok, N. AU - Spitzbart, B. AU - Seward, F. AU - Kenyon, S. AU - Barnes, T. AU - Pasachoff, J. M. JO - Journal of the Royal Astronomical Society of Canada VL - 99 Y1 - 2005/08/1 SP - 136 EP - 137 UR - https://ui.adsabs.harvard.edu/abs/2005JRASC..99..136E N2 - 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. SN - 0035-872X ER - TY - CONF TI - h Persei: Young Star Cluster in X-rays AU - Bizunok, Natalya AU - Wolk, S. J. AU - Evans, N. R. AU - Spitzbart, B. AU - Seward, F. AU - Kenyon, S. AU - Barnes, T. AU - Pasachoff, J. M. AD - 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) JO - Star Formation in the Era of Three Great Observatories Y1 - 2005/07/1 SP - 48 UR - https://ui.adsabs.harvard.edu/abs/2005sfet.confE..48B N2 - 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. ER - TY - JOUR TI - Discovery of a 105 ms X-Ray Pulsar in Kesteven 79: On the Nature of Compact Central Objects in Supernova Remnants AU - Gotthelf, E. V. AU - Halpern, J. P. AU - Seward, F. D. AD - AA(Columbia University, Department of Astronomy and Astrophysics), AB(Columbia University, Department of Astronomy and Astrophysics), AC(Smithsonian Astrophysical Observatory) JO - The Astrophysical Journal VL - 627 Y1 - 2005/07/1 SP - 390 EP - 396 KW - ISM: Individual: Name: Kesteven 79 KW - Stars: Pulsars: Individual: Alphanumeric: CXOU J185238.6+004020 KW - Stars: Pulsars: Individual: Alphanumeric: PSR J1852+0040 KW - Stars: Neutron KW - ISM: Supernova Remnants KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/2005ApJ...627..390G N2 - 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. PB - IOP DO - 10.1086/430300 C1 - eprint: arXiv:astro-ph/0503424 SN - 0004-637X ER - TY - MISC TI - VizieR Online Data Catalog: Second Ariel X-Ray Catalogue (2A) (Cooke+ 1978) AU - Cooke, B. A. AU - Ricketts, M. J. AU - Maccacaro, T. AU - Pye, J. P. AU - Elvis, M. AU - Watson, M. G. AU - Griffiths, R. E. AU - Pounds, K. A. AU - McHardy, I. M. AU - Maccagni, D. AU - Seward, F. D. AU - Page, C. G. AU - Turner, M. J. L. JO - VizieR Online Data Catalog VL - 9002 Y1 - 2005/05/1 SP - IX/2 KW - X-ray sources UR - https://ui.adsabs.harvard.edu/abs/2005yCat.9002....0C N2 - 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). ER - TY - CONF TI - The Open Cluster h Per as Seen by Chandra AU - Bizunok, N. S. AU - Evans, N. R. AU - Wolk, S. J. AU - Spitzbart, B. AU - Seward, F. D. AU - Kenyon, S. J. AU - Barnes, T. G. AU - Pasachoff, J. M. AD - 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) JO - American Astronomical Society Meeting Abstracts #206 VL - 206 Y1 - 2005/05/1 SP - 36.04 UR - https://ui.adsabs.harvard.edu/abs/2005AAS...206.3604B N2 - 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 ER - TY - CONF TI - How to Write an X-ray Proposal AU - Seward, F. D. AD - AA(Smithsonian Astrophysical Observatory) JO - X-Ray and Radio Connections Y1 - 2005/04/1 SP - 6.04 KW - X-ray KW - radio KW - proposals UR - https://ui.adsabs.harvard.edu/abs/2005xrrc.procE6.04S N2 - 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. ER - TY - JOUR TI - Unveiling Eta Carinae with Chandra AU - Corcoran, M. F. AU - Seward, F. D. AU - Henley, D. B. AU - Hamaguchi, K. AD - AA(Universities Space Research Association), AB(Smithsonian Astrophysical Observatory), AC(University of Birmingham, UK), AD(NRC) JO - Chandra News VL - 12 Y1 - 2005/01/1 SP - 1 EP - 5 UR - https://ui.adsabs.harvard.edu/abs/2005ChNew..12....1C ER - TY - JOUR TI - How to Write an X-ray Proposal AU - Seward, Fred JO - Chandra News VL - 12 Y1 - 2005/01/1 SP - 29 EP - 30 UR - https://ui.adsabs.harvard.edu/abs/2005ChNew..12...29S ER - TY - CONF TI - The Supernova Remnant and Superbubble Components of the N206 Complex AU - Williams, R. N. M. AU - Chu, Y. -H. AU - Dickel, J. R. AU - Gruendl, R. A. AU - Dunne, B. C. AU - Guerrero, M. A. AU - Seward, F. D. AU - Hobbs, G. AU - Magellanic Cloud Emission-Line Survey AD - 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) JO - American Astronomical Society Meeting Abstracts VL - 205 Y1 - 2004/12/1 SP - 70.05 UR - https://ui.adsabs.harvard.edu/abs/2004AAS...205.7005W N2 - 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. ER - TY - CONF TI - Chandra Observation of the Magellanic Cloud Supernova Remnant 0454-672 in N9 AU - Seward, F. D. AU - Chu, Y. -H. AU - Dickel, J. R. AU - Williams, R. M. AU - Smith, C. AD - AA(Smithsonian Astrophysical Observatory), AB(University of Illinois System), AC(University of Illinois System), AD(University of Illinois System), AE(Cerro Tololo Interamerican Observatory) JO - American Astronomical Society Meeting Abstracts VL - 205 Y1 - 2004/12/1 SP - 101.05 UR - https://ui.adsabs.harvard.edu/abs/2004AAS...20510105S N2 - 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. ER - TY - JOUR TI - Chandra Observations of Associates of η Carinae. II. Spectra AU - Evans, Nancy Remage AU - Schlegel, Eric M. AU - Waldron, Wayne L. AU - Seward, Frederick D. AU - Krauss, Miriam I. AU - Nichols, Joy AU - Wolk, Scott J. AD - 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) JO - The Astrophysical Journal VL - 612 Y1 - 2004/09/1 SP - 1065 EP - 1080 KW - Stars: Individual: Constellation Name: η Carinae KW - X-Rays: Stars KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/2004ApJ...612.1065E N2 - 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. PB - IOP DO - 10.1086/422543 C1 - eprint: arXiv:astro-ph/0405587 SN - 0004-637X ER - TY - CONF TI - Search for Thermal X-rays from the Crab Nebula AU - Seward, F. D. AU - Gorenstein, P. AU - Slane, P. O. AU - Tucker, W. H. AU - Smith, R. AU - Fesen, R. A. AD - 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) JO - AAS/High Energy Astrophysics Division #8 VL - 8 Y1 - 2004/08/1 SP - 28.06 UR - https://ui.adsabs.harvard.edu/abs/2004HEAD....8.2806S N2 - 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. ER - TY - JOUR TI - Chandra View of Kesteven 79: A Nearly Isothermal Supernova Remnant with Rich Spatial Structure AU - Sun, M. AU - Seward, F. D. AU - Smith, R. K. AU - Slane, P. O. AD - AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics) JO - The Astrophysical Journal VL - 605 Y1 - 2004/04/1 SP - 742 EP - 750 KW - Conduction KW - ISM: Individual: Name: Kesteven 79 KW - Stars: Winds KW - Outflows KW - ISM: Supernova Remnants KW - X-Rays: ISM KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/2004ApJ...605..742S N2 - 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. PB - IOP DO - 10.1086/382666 C1 - eprint: arXiv:astro-ph/0401165 SN - 0004-637X ER - TY - JOUR TI - X-Ray Observations of the Compact Source in CTA 1 AU - Slane, Patrick AU - Zimmerman, Erik R. AU - Hughes, John P. AU - Seward, Frederick D. AU - Gaensler, Bryan M. AU - Clarke, Melanie J. AD - 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) JO - The Astrophysical Journal VL - 601 Y1 - 2004/02/1 SP - 1045 EP - 1049 KW - ISM: Individual: Alphanumeric: CTA 1 KW - Stars: Individual: Alphanumeric: RX J0007.0+7302 KW - Stars: Individual: Alphanumeric: 3EG J0010+7309 KW - Stars: Neutron KW - ISM: Supernova Remnants KW - X-Rays: ISM KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/2004ApJ...601.1045S N2 - 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. PB - IOP DO - 10.1086/380498 C1 - eprint: arXiv:astro-ph/0310250 SN - 0004-637X ER - TY - CONF TI - The Chandra Supernova Remnant Catalog AU - Seward, F. AU - Smith, R. AU - Hagler, J. AU - Portolese, L. AU - Gaetz, T. AU - Slane, P. AU - Koo, B. -C. AU - Lee, J. -J. JO - Young Neutron Stars and Their Environments VL - 218 Y1 - 2004/01/1 SP - 93 UR - https://ui.adsabs.harvard.edu/abs/2004IAUS..218...93S N2 - 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. SN - 1743-9221 ER - TY - MISC TI - Thermal Emission from the Crab Nebula AU - Seward, Frederick JO - Chandra Proposal Y1 - 2003/09/1 SP - 1451 KW - Chandra Proposal ID #05500128 UR - https://ui.adsabs.harvard.edu/abs/2003cxo..prop.1451S N2 - 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. ER - TY - JOUR TI - Chandra Observations of Associates of η Carinae. I. Luminosities AU - Evans, Nancy Remage AU - Seward, Frederick D. AU - Krauss, Miriam I. AU - Isobe, Takashi AU - Nichols, Joy AU - Schlegel, Eric M. AU - Wolk, Scott J. AD - AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory), AC(Smithsonian Astrophysical Observatory), AD(Smithsonian Astrophysical Observatory) JO - The Astrophysical Journal VL - 589 Y1 - 2003/05/1 SP - 509 EP - 525 KW - Galaxy: Open Clusters and Associations: Individual: Name: Trumpler 14 KW - Galaxy: Open Clusters and Associations: Individual: Name: Trumpler 16 KW - X-Rays: Stars KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/2003ApJ...589..509E N2 - 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. PB - IOP DO - 10.1086/374355 C1 - eprint: arXiv:astro-ph/0301485 SN - 0004-637X ER - TY - MISC TI - XMM-Newton Proposal 02049702 AU - Seward, Frederick JO - XMM-Newton Proposal Y1 - 2003/03/1 SP - 264 KW - CXOUJ185238.6+00402 KW - CXOUJ185238.6+00402 KW - XMM-Newton Proposal 02049702 UR - https://ui.adsabs.harvard.edu/abs/2003xmm..prop..264S N2 - 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. ER - TY - JOUR TI - A Compact Central Object in the Supernova Remnant Kesteven 79 AU - Seward, F. D. AU - Slane, P. O. AU - Smith, R. K. AU - Sun, M. AD - AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory), AC(Smithsonian Astrophysical Observatory), AD(Harvard College Observatory) JO - The Astrophysical Journal VL - 584 Y1 - 2003/02/1 SP - 414 EP - 417 KW - ISM: Individual: Name: Kesteven 79 KW - Stars: Neutron KW - ISM: Supernova Remnants KW - X-Rays: Stars KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/2003ApJ...584..414S N2 - 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. PB - IOP DO - 10.1086/345600 C1 - eprint: arXiv:astro-ph/0210496 SN - 0004-637X ER - TY - MISC TI - Observing the Thermal Composite SNR Kes 27 AU - Seward, Frederick JO - Chandra Proposal Y1 - 2002/09/1 SP - 1208 KW - Chandra Proposal ID #04500364 UR - https://ui.adsabs.harvard.edu/abs/2002cxo..prop.1208S N2 - 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. ER - TY - MISC TI - Supernova Remnants in the Magellanic Clouds AU - Seward, Frederick JO - Chandra Proposal Y1 - 2002/09/1 SP - 1206 KW - Chandra Proposal ID #04500278 UR - https://ui.adsabs.harvard.edu/abs/2002cxo..prop.1206S N2 - 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. ER - TY - CONF TI - Associates of Eta Car: New Insights AU - Evans, N. R. AU - Seward, F. D. AU - Krauss, M. I. AU - Nichols, J. AU - Schlegel, E. M. AU - Wolk, S. J. AU - Waldron, W. L. AD - 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) JO - American Astronomical Society Meeting Abstracts #200 VL - 200 Y1 - 2002/05/1 SP - 74.12 UR - https://ui.adsabs.harvard.edu/abs/2002AAS...200.7412E N2 - 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 ER - TY - CONF TI - Chandra view of SNR Kes 79 AU - Sun, Ming AU - Seward, Frederick AU - Smith, Randall AU - Slane, Patrick AD - AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics) JO - APS April Meeting Abstracts Y1 - 2002/04/1 SP - N17.036 UR - https://ui.adsabs.harvard.edu/abs/2002APS..APRN17036S N2 - 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. ER - TY - CONF TI - A Central Source in the Supernova Remnant Kes 79 AU - Seward, F. AU - Slane, P. AU - Smith, R. AU - Sun, M. AD - AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory), AC(Smithsonian Astrophysical Observatory), AD(Smithsonian Astrophysical Observatory) JO - APS April Meeting Abstracts Y1 - 2002/04/1 SP - N17.035 UR - https://ui.adsabs.harvard.edu/abs/2002APS..APRN17035S N2 - 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. ER - TY - JOUR TI - Discovery of X-Ray Pulsations from the Compact Central Source in the Supernova Remnant 3C 58 AU - Murray, Stephen S. AU - Slane, Patrick O. AU - Seward, Fredrick D. AU - Ransom, Scott M. AU - Gaensler, Bryan M. AD - 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) JO - The Astrophysical Journal VL - 568 Y1 - 2002/03/1 SP - 226 EP - 231 KW - ISM: Individual: Alphanumeric: 3C 58 KW - Stars: Pulsars: Individual: Alphanumeric: PSR J0205+6449 KW - Stars: Neutron KW - ISM: Supernova Remnants KW - X-Rays: Stars KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/2002ApJ...568..226M N2 - 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. PB - IOP DO - 10.1086/338766 C1 - eprint: arXiv:astro-ph/0108489 SN - 0004-637X ER - TY - JOUR TI - An ASCA Study of the W51 Complex AU - Koo, Bon-Chul AU - Lee, Jae-Joon AU - Seward, Frederick D. AD - AA(Seoul National University, Department of Physics and Astronomy), AB(Seoul National University, Department of Physics and Astronomy), AC(Harvard Smithsonian Center for Astrophysics) JO - The Astronomical Journal VL - 123 Y1 - 2002/03/1 SP - 1629 EP - 1638 KW - ISM: H II Regions -ISM: Individual: Alphanumeric: W51 KW - Stars: Formation KW - ISM: Supernova Remnants -X-rays: ISM KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/2002AJ....123.1629K N2 - 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. PB - IOP DO - 10.1086/339179 C1 - eprint: arXiv:astro-ph/0112367 SN - 0004-6256 ER - TY - CONF TI - High-Precision X-ray Timing of the Pulsar in 3C 58 AU - Ransom, S. AU - Kaspi, V. AU - Gaensler, B. AU - Murray, S. AU - Gotthelf, E. AU - Slane, P. AU - Seward, F. JO - 34th COSPAR Scientific Assembly VL - 34 Y1 - 2002/01/1 SP - 2928 UR - https://ui.adsabs.harvard.edu/abs/2002cosp...34E2928R N2 - 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. ER - TY - CONF TI - Low-Mass Neutron Stars as Anomalous Pulsars AU - Seward, F. D. JO - Neutron Stars in Supernova Remnants VL - 271 Y1 - 2002/01/1 SP - 270 KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/2002ASPC..271..270S N2 - 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. DO - 10.48550/arXiv.astro-ph/0112047 C1 - eprint: arXiv:astro-ph/0112047 SN - 1050-3390 ER - TY - CONF TI - Stars Grouped with η Car AU - Evans, Nancy Remage AU - Seward, Fredrick D. JO - Two Years of Science with Chandra Y1 - 2001/09/1 SP - 95 KW - NORMAL STARS AND WHITE DWARFS UR - https://ui.adsabs.harvard.edu/abs/2001tysc.confE..95E N2 - 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. ER - TY - MISC TI - An Atlas of Chandra Supernova Remnants AU - Seward, Frederick JO - Chandra Proposal Y1 - 2001/09/1 SP - 3951 UR - https://ui.adsabs.harvard.edu/abs/2001cxo..prop.3951S N2 - 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. ER - TY - MISC TI - Search for the Outer Shell of the Crab Nebula AU - Seward, Frederick JO - Chandra Proposal Y1 - 2001/09/1 SP - 855 KW - Chandra Proposal ID #03500419 UR - https://ui.adsabs.harvard.edu/abs/2001cxo..prop..855S N2 - 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. ER - TY - JOUR TI - Early Chandra X-Ray Observations of η Carinae AU - Seward, F. D. AU - Butt, Y. M. AU - Karovska, M. AU - Prestwich, A. AU - Schlegel, E. M. AU - Corcoran, M. AD - 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) JO - The Astrophysical Journal VL - 553 Y1 - 2001/06/1 SP - 832 EP - 836 KW - Stars: Early-Type KW - Stars: Individual: Constellation Name: η Carinae KW - X-Rays: Stars KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/2001ApJ...553..832S N2 - 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. PB - IOP DO - 10.1086/320961 C1 - eprint: arXiv:astro-ph/0101206 SN - 0004-637X ER - TY - JOUR TI - Chandra Observations of the Young Pulsar PSR B0540-69 AU - Kaaret, P. AU - Marshall, H. L. AU - Aldcroft, T. L. AU - Graessle, D. E. AU - Karovska, M. AU - Murray, S. S. AU - Rots, A. H. AU - Schulz, N. S. AU - Seward, F. D. AD - 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) JO - The Astrophysical Journal VL - 546 Y1 - 2001/01/1 SP - 1159 EP - 1167 KW - Stars: Pulsars: General KW - Stars: Pulsars: Individual: Alphanumeric: PSR 0540-69 KW - Stars: Neutron KW - ISM: Supernova Remnants KW - X-Rays: Stars KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/2001ApJ...546.1159K N2 - 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. PB - IOP DO - 10.1086/318287 C1 - eprint: arXiv:astro-ph/0008388 SN - 0004-637X ER - TY - MISC TI - The Thermal Composite SNR Kes 79 AU - Seward, Frederick JO - Chandra Proposal Y1 - 2000/09/1 SP - 614 KW - Chandra Proposal ID #02500707 UR - https://ui.adsabs.harvard.edu/abs/2000cxo..prop..614S N2 - 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. ER - TY - JOUR TI - Settling onto the Main Sequence: ROSAT Observations of H and χ Persei AU - Evans, Nancy Remage AU - Seward, Fredrick D. AD - AA(Smithsonian Astrophysical Observatory) JO - The Astrophysical Journal VL - 538 Y1 - 2000/08/1 SP - 777 EP - 782 KW - open clusters and associations: individual (χ Persei KW - h Persei) KW - Stars: Formation KW - Stars: Pre-Main-Sequence KW - X-Rays: Stars UR - https://ui.adsabs.harvard.edu/abs/2000ApJ...538..777E N2 - 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. PB - IOP DO - 10.1086/309162 SN - 0004-637X ER - TY - JOUR TI - ROSAT Observations of the Vela Pulsar AU - Seward, F. D. AU - Alpar, M. A. AU - Flanagan, C. AU - Kızıloǧlu, Ü. AU - Markwardt, C. AU - McCulloch, P. AU - Ögelman, H. AD - 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) JO - The Astrophysical Journal VL - 536 Y1 - 2000/06/1 SP - 948 EP - 953 KW - Stars: Pulsars: Individual: Name: Vela pulsar KW - Stars: Neutron KW - X-Rays: Stars KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/2000ApJ...536..948S N2 - 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. PB - IOP DO - 10.1086/308961 C1 - eprint: arXiv:astro-ph/0004015 SN - 0004-637X ER - TY - JOUR TI - Chandra Images AU - Evans, Nancy Remage AU - Canizares, Claude AU - Flanagan, Kathryn AU - Davis, David AU - Houck, John AU - Kraft, Ralph P. AU - Schwartz, Dan AU - Murray, Steve AU - Garcia, Mike AU - Weisskopf, Martin AU - Garmire, Gordon AU - Feigelson, Eric AU - Broos, Patrick AU - Hillenbrand, Lynne AU - Pravdo, Steven AU - Townsley, Leisa AU - Tsuboi, Yohko AU - Seward, Fred AU - Harnden, Rick AU - Wolk, Scott JO - Chandra News VL - 7 Y1 - 2000/05/1 SP - 7 UR - https://ui.adsabs.harvard.edu/abs/2000ChNew...7....7E ER - TY - JOUR TI - Finding Chandra Targets and Target Parameters AU - Seward, Fred JO - Chandra News VL - 7 Y1 - 2000/05/1 SP - 15 UR - https://ui.adsabs.harvard.edu/abs/2000ChNew...7...15S ER - TY - JOUR TI - The Scheduling of Observations AU - Seward, Fred JO - Chandra News VL - 7 Y1 - 2000/05/1 SP - 14 UR - https://ui.adsabs.harvard.edu/abs/2000ChNew...7...14S ER - TY - JOUR TI - Chandra Observations of the Crab-like Supernova Remnant G21.5-0.9 AU - Slane, Patrick AU - Chen, Yang AU - Schulz, Norbert S. AU - Seward, Frederick D. AU - Hughes, John P. AU - Gaensler, Bryan M. AD - 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) JO - The Astrophysical Journal VL - 533 Y1 - 2000/04/1 SP - L29 EP - L32 KW - ISM: INDIVIDUAL: ALPHANUMERIC: G21.5-0.9 KW - ISM: SUPERNOVA REMNANTS KW - X-RAYS: ISM KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/2000ApJ...533L..29S N2 - 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. PB - IOP DO - 10.1086/312589 C1 - eprint: arXiv:astro-ph/0001536 SN - 0004-637X ER - TY - CHAP TI - X-Ray Astronomy AU - Seward, Frederick D. JO - Allen's Astrophysical Quantities Y1 - 2000/01/1 SP - 183 UR - https://ui.adsabs.harvard.edu/abs/2000asqu.book..183S ER - TY - CONF TI - Chandra Observation of Eta Carina AU - Seward, F. D. AU - Evans, N. R. AU - Karovska, M. AU - Prestwich, A. AU - Schlegel, E. M. AU - Corcoran, M. AU - Townsley, L. AD - 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) JO - American Astronomical Society Meeting Abstracts VL - 195 Y1 - 1999/12/1 SP - 75.14 UR - https://ui.adsabs.harvard.edu/abs/1999AAS...195.7514S N2 - 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. ER - TY - JOUR TI - DA 530: A Supernova Remnant in a Stellar Wind Bubble AU - Landecker, T. L. AU - Routledge, D. AU - Reynolds, S. P. AU - Smegal, R. J. AU - Borkowski, K. J. AU - Seward, F. D. AD - 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) JO - The Astrophysical Journal VL - 527 Y1 - 1999/12/1 SP - 866 EP - 878 KW - ISM: BUBBLES KW - ISM: INDIVIDUAL (DA 530) KW - RADIO CONTINUUM: ISM KW - ISM: SUPERNOVA REMNANTS KW - X-RAYS: ISM KW - ISM: Bubbles KW - ISM: individual (DA 530) KW - Radio Continuum: ISM KW - ISM: Supernova Remnants KW - X-Rays: ISM UR - https://ui.adsabs.harvard.edu/abs/1999ApJ...527..866L N2 - 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. PB - IOP DO - 10.1086/308100 SN - 0004-637X ER - TY - MISC TI - VizieR Online Data Catalog: X-ray observations of galactic Supernova Remnants (Seward, 1990) AU - Seward, F. D. JO - VizieR Online Data Catalog VL - 207 Y1 - 1999/04/1 SP - J/ApJS/73/781 KW - Supernova remnants KW - X-ray sources UR - https://ui.adsabs.harvard.edu/abs/1999yCat..20730781S N2 - 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). DO - 10.26093/cds/vizier.20730781 ER - TY - CONF TI - Settling onto the Main Sequence: ROSAT Observations of H and chi Per AU - Evans, Nancy Remage AU - Seward, Fredrick D. AD - AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory) JO - AAS/High Energy Astrophysics Division #4 VL - 4 Y1 - 1999/04/1 SP - 09.01 UR - https://ui.adsabs.harvard.edu/abs/1999HEAD....4.0901E N2 - 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. ER - TY - CONF TI - ROSAT Observations of the VELA Pulsar AU - Seward, F. D. AU - Alpar, A. AU - Flanagan, C. AU - Markwardt, C. AU - McCulloch, P. AU - Ogelman, H. AD - 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) JO - AAS/High Energy Astrophysics Division #4 VL - 4 Y1 - 1999/04/1 SP - 29.03 UR - https://ui.adsabs.harvard.edu/abs/1999HEAD....4.2903S N2 - 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. ER - TY - JOUR TI - Peer Review AU - Seward, Fred JO - Chandra News VL - 6 Y1 - 1999/02/1 SP - 16 UR - https://ui.adsabs.harvard.edu/abs/1999ChNew...6...16S ER - TY - JOUR TI - AXAF Users' Committee AU - Seward, Fred JO - Chandra News VL - 5 Y1 - 1997/12/1 SP - 29 UR - https://ui.adsabs.harvard.edu/abs/1997ChNew...5...29S ER - TY - JOUR TI - Nonthermal X-Ray Emission from CTA 1 AU - Slane, Patrick AU - Seward, Frederick D. AU - Bandiera, Rino AU - Torii, Ken'ichi AU - Tsunemi, Hiroshi AD - 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) JO - The Astrophysical Journal VL - 485 Y1 - 1997/08/1 SP - 221 EP - 227 KW - ISM: Individual: Alphanumeric: CTA 1 KW - ISM: Supernova Remnants KW - X-Rays: ISM UR - https://ui.adsabs.harvard.edu/abs/1997ApJ...485..221S N2 - 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. PB - IOP DO - 10.1086/304416 SN - 0004-637X ER - TY - MISC TI - Observation of Crab-Like Supernova Remnants AU - Seward, Frederick JO - RXTE Proposal Y1 - 1997/01/1 SP - 20259 UR - https://ui.adsabs.harvard.edu/abs/1997rxte.prop20259S N2 - 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. ER - TY - CONF TI - VERITAS: The Very Energetic Radiation Imaging Telescope Array System. AU - Weekes, T. C. AU - Akerlof, C. AU - Biller, S. AU - Breslin, A. C. AU - Catanese, M. AU - Carter-Lewis, D. A. AU - Cawley, M. F. AU - Dingus, B. AU - Fazio, G. G. AU - Fegan, D. J. AU - Finley, J. AU - Fishman, G. AU - Gaidos, J. AU - Gillanders, G. H. AU - Gorham, P. AU - Grindlay, J. E. AU - Hillas, A. M. AU - Huchra, J. AU - Kaaret, P. AU - Kertzman, M. AU - Kieda, D. AU - Krennrich, F. AU - Lamb, R. C. AU - Lang, M. J. AU - Marscher, A. P. AU - Matz, S. AU - McKay, T. AU - Muller, D. AU - Ong, R. AU - Purcell, W. AU - Rose, H. J. AU - Sembroski, G. AU - Seward, F. D. AU - Slane, P. AU - Swordy, S. AU - Tumer, T. AU - Ulmer, M. AU - Urban, M. AU - Wilkes, B. JO - International Cosmic Ray Conference VL - 5 Y1 - 1997/01/1 SP - 173 KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1997ICRC....5..173W N2 - 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). DO - 10.48550/arXiv.astro-ph/9706143 C1 - eprint: arXiv:astro-ph/9706143 ER - TY - JOUR TI - ROSAT Observations of Two Southern Supernova Remnants AU - Seward, F. D. AU - Kearns, K. E. AU - Rhode, K. L. JO - The Astrophysical Journal VL - 471 Y1 - 1996/11/1 SP - 887 KW - ISM: SUPERNOVA REMNANTS KW - ISM: INDIVIDUAL ALPHANUMERIC: G327.1-1.1 KW - ISM: INDIVIDUAL ALPHANUMERIC: G327.4+0.4 KW - ISM: INDIVIDUAL NAME: KESTEVEN 27 KW - X-RAYS: ISM UR - https://ui.adsabs.harvard.edu/abs/1996ApJ...471..887S N2 - 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. PB - IOP DO - 10.1086/178015 SN - 0004-637X ER - TY - JOUR TI - AXAF Users' Committee Report AU - Seward, Fred JO - Chandra News VL - 4 Y1 - 1996/09/1 SP - 19 UR - https://ui.adsabs.harvard.edu/abs/1996ChNew...4...19S ER - TY - CONF TI - Two southern SNR: G 327.1-1.1 and Kes 27. AU - Seward, F. D. AU - Kearns, K. E. AU - Rhode, K. L. JO - Roentgenstrahlung from the Universe Y1 - 1996/02/1 SP - 277 EP - 278 KW - Supernova Remnants: X-Ray Sources KW - Supernova Remnants: X-Ray Maps KW - Supernova Remnants: Radio Maps KW - Supernova Remnants: Structure UR - https://ui.adsabs.harvard.edu/abs/1996rftu.proc..277S N2 - 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. ER - TY - BOOK TI - Exploring the X-Ray Universe AU - Seward, Frederick D. AU - Charles, Philip A. AD - AA(University of Oxford, UK), AB(Smithsonian Astrophysical Observatory) JO - Exploring the X-Ray Universe Y1 - 1995/11/1 SP - 414 KW - X-RAY ASTRONOMY UR - https://ui.adsabs.harvard.edu/abs/1995exru.book.....S N2 - 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. ER - TY - JOUR TI - X-Ray Emission from the Supernova Remnant CTA 1 AU - Seward, F. D. AU - Schmidt, B. AU - Slane, P. JO - The Astrophysical Journal VL - 453 Y1 - 1995/11/1 SP - 284 KW - GALAXIES: SEYFERT KW - ISM: INDIVIDUAL ALPHANUMERIC: CTA 1 KW - ISM: SUPERNOVA REMNANTS KW - X-RAYS: ISM UR - https://ui.adsabs.harvard.edu/abs/1995ApJ...453..284S N2 - 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. PB - IOP DO - 10.1086/176388 SN - 0004-637X ER - TY - JOUR TI - AXAF Users' Committee Report AU - Seward, Fred JO - Chandra News VL - 3 Y1 - 1995/09/1 SP - 11 UR - https://ui.adsabs.harvard.edu/abs/1995ChNew...3...11S ER - TY - JOUR TI - A ROSAT-detected, New Galactic Supernova Remnant in Sagittarius, G13.3-1.3 AU - Seward, F. D. AU - Dame, T. M. AU - Fesen, R. A. AU - Aschenbach, B. JO - The Astrophysical Journal VL - 449 Y1 - 1995/08/1 SP - 681 KW - ISM: SUPERNOVA REMNANTS KW - ISM: INDIVIDUAL ALPHANUMERIC: G13.3-1.3 KW - X-RAYS: ISM UR - https://ui.adsabs.harvard.edu/abs/1995ApJ...449..681S N2 - 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. PB - IOP DO - 10.1086/176089 SN - 0004-637X ER - TY - JOUR TI - ROSAT Observations of the Supernova Remnant W51C AU - Koo, Bon-Chul AU - Kim, Kee-Tae AU - Seward, Frederick D. JO - The Astrophysical Journal VL - 447 Y1 - 1995/07/1 SP - 211 KW - ISM: INDIVIDUAL ALPHANUMERIC: W51 KW - ISM: SUPERNOVA REMNANTS KW - RADIO CONTINUUM: ISM KW - X-RAYS: ISM UR - https://ui.adsabs.harvard.edu/abs/1995ApJ...447..211K N2 - 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. PB - IOP DO - 10.1086/175867 SN - 0004-637X ER - TY - JOUR TI - A ROSAT Observation of the Supernova Remnant Kesteven 79 AU - Seward, F. D. AU - Velusamy, T. AD - AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics) JO - The Astrophysical Journal VL - 439 Y1 - 1995/02/1 SP - 715 KW - Interstellar Matter KW - Radio Observation KW - Stellar Envelopes KW - Supernova Remnants KW - X Ray Astronomy KW - X Ray Spectra KW - Astronomical Models KW - Brightness KW - Emission Spectra KW - Luminosity KW - Rosat Mission KW - Shock Wave Luminescence KW - Spectrum Analysis KW - Astrophysics KW - ISM: SUPERNOVA REMNANTS KW - ISM: INDIVIDUAL NAME: KESTEVEN 79 KW - X-RAYS: ISM UR - https://ui.adsabs.harvard.edu/abs/1995ApJ...439..715S N2 - 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. PB - IOP DO - 10.1086/175211 SN - 0004-637X ER - TY - JOUR TI - X-ray evidence for the association of G11.2-0.3 with the supernova of 386 AD. AU - Reynolds, S. P. AU - Lyutikov, M. AU - Blandford, R. D. AU - Seward, F. D. JO - Monthly Notices of the Royal Astronomical Society VL - 271 Y1 - 1994/11/1 SP - L1 EP - L4 KW - Supernova Remnants: X-Ray Maps KW - Supernova Remnants: Shock Waves KW - Supernova Remnants: Distances UR - https://ui.adsabs.harvard.edu/abs/1994MNRAS.271L...1R N2 - 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. PB - OUP DO - 10.1093/mnras/271.1.L1 SN - 0035-8711 ER - TY - JOUR TI - AXAF Users' Committee Report AU - Seward, Fred JO - Chandra News VL - 2 Y1 - 1994/08/1 SP - 13 UR - https://ui.adsabs.harvard.edu/abs/1994ChNew...2...13S ER - TY - JOUR TI - ROSAT observations of the jupiter aurora AU - Waite, J. H., Jr. AU - Bagenal, F. AU - Seward, F. AU - Na, C. AU - Gladstone, G. R. AU - Cravens, T. E. AU - Hurley, K. C. AU - Clarke, J. T. AU - Elsner, R. AU - Stern, S. A. AD - 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) JO - Journal of Geophysical Research VL - 99 Y1 - 1994/08/1 SP - 14799 EP - 14810 KW - Auroras KW - Bremsstrahlung KW - Jupiter (Planet) KW - Proportional Counters KW - Ions KW - Iue KW - Line Spectra KW - Particle Precipitation KW - Rosat Mission KW - X Ray Spectra KW - Magnetospheric Physics: Auroral phenomena KW - Atmospheric Composition and Structure: Airglow and aurora KW - Magnetospheric Physics: Energetic particles KW - precipitating KW - Magnetospheric Physics: Planetary magnetospheres UR - https://ui.adsabs.harvard.edu/abs/1994JGR....9914799W N2 - 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]. DO - 10.1029/94JA01005 SN - 0148-0227 ER - TY - JOUR TI - The Outer Shell of SNR 0540-69.3 AU - Seward, F. D. AU - Harnden, F. R., Jr. AD - AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics) JO - The Astrophysical Journal VL - 421 Y1 - 1994/02/1 SP - 581 KW - Astronomical Models KW - Magellanic Clouds KW - Shock Waves KW - Spaceborne Astronomy KW - Supernova Remnants KW - X Ray Astronomy KW - Luminosity KW - Rosat Mission KW - Astronomy KW - GALAXIES: MAGELLANIC CLOUDS KW - ISM: INDIVIDUAL ALPHANUMERIC: 0540-69.3 KW - ISM: SUPERNOVA REMNANTS KW - X-RAYS: ISM UR - https://ui.adsabs.harvard.edu/abs/1994ApJ...421..581S N2 - 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. PB - IOP DO - 10.1086/173673 SN - 0004-637X ER - TY - RPRT TI - Investigation relative to the Roentgen Satellite (ROSAT) AU - Elvis, Martin S. AU - Primini, Francis A. AU - Fabbiano, Guiseppina AU - Harris, Daniel E. AU - Jones-Forman, Christine AU - Trinchieri, Ginevra AU - Golub, Leon AU - Bookbinder, Jay AU - Seward, Frederick D. AU - Zombeck, Martin V. AD - 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) JO - Smithsonian Astrophysical Observatory Report Y1 - 1994/01/1 KW - Radio Astronomy KW - Rosat Mission KW - Spaceborne Astronomy KW - Supernova Remnants KW - X Ray Astronomy KW - X Ray Sources KW - Andromeda Galaxy KW - Astrophysics KW - Cataclysmic Variables KW - Cygnus Constellation KW - Gravitational Lenses KW - Magellanic Clouds KW - Quasars KW - Astronomy UR - https://ui.adsabs.harvard.edu/abs/1994sao..rept.....E N2 - 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. ER - TY - CONF TI - X-ray Observations of Two Radio-Bright Supernova Remnants AU - Reynolds, S. P. AU - Seward, F. D. AU - Blandford, R. D. AD - AA(North Carolina State University), AB(Harvard Smithsonian Center for Astrophysics), AC(California Institute of Technology) JO - American Astronomical Society Meeting Abstracts VL - 183 Y1 - 1993/12/1 SP - 83.03 UR - https://ui.adsabs.harvard.edu/abs/1993AAS...183.8303R N2 - 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. ER - TY - CONF TI - ROSAT Observations of the Supernova Remnant Kes 79 AU - Seward, F. D. AU - Velusamy, T. JO - American Astronomical Society Meeting Abstracts VL - 183 Y1 - 1993/12/1 SP - 83.02 UR - https://ui.adsabs.harvard.edu/abs/1993AAS...183.8302S ER - TY - JOUR TI - Neutron Stars. (Book Reviews: Isolated Pulsars.) AU - Seward, Fred JO - Science VL - 262 Y1 - 1993/10/1 SP - 444 EP - 445 UR - https://ui.adsabs.harvard.edu/abs/1993Sci...262..444S DO - 10.1126/science.262.5132.444 SN - 0036-8075 ER - TY - JOUR TI - Neutron Stars. (Book Reviews: Isolated Pulsars.) AU - Seward, Fred JO - Science VL - 262 Y1 - 1993/10/1 SP - 444 EP - 445 UR - https://ui.adsabs.harvard.edu/abs/1993Sci...262..444V DO - 10.1126/science.262.5132.444 SN - 0036-8075 ER - TY - JOUR TI - The AXAF Users' Committee AU - Seward, Fred JO - Chandra News VL - 1 Y1 - 1993/09/1 SP - 4 UR - https://ui.adsabs.harvard.edu/abs/1993ChNew...1....4S ER - TY - CONF TI - An X-ray counterpart to the 5 March 1979 gamma ray burst? AU - Rothschild, R. E. AU - Lingenfelter, R. E. AU - Seward, F. D. AU - Vancura, O. JO - Compton Gamma-ray Observatory VL - 280 Y1 - 1993/01/1 SP - 808 EP - 812 UR - https://ui.adsabs.harvard.edu/abs/1993AIPC..280..808R N2 - 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. PB - AIP DO - 10.1063/1.44225 SN - 0094-243X ER - TY - CONF TI - Verification of the PROS Timing Analysis Package AU - Manning, K. R. AU - Conroy, M. A. AU - Deponte, J. AU - Moran, J. F. AU - Primini, F. A. AU - Seward, F. D. AU - Aschenbach, B. AD - 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) JO - Astronomical Data Analysis Software and Systems II VL - 52 Y1 - 1993/01/1 SP - 484 UR - https://ui.adsabs.harvard.edu/abs/1993ASPC...52..484M SN - 1050-3390 ER - TY - JOUR TI - SNRs MSH 15-56 and CTA AU - Wang, Zhen-Ru AU - Qu, Qin-Yue AU - Seward, Fred AD - AA(Nanjing University, China), AB(Nanjing University, China), AC(Harvard Smithsonian Center for Astrophysics) JO - Chinese Astronomy and Astrophysics VL - 16 Y1 - 1992/09/1 SP - 278 EP - 283 KW - H Alpha Line KW - Satellite Observation KW - Spaceborne Astronomy KW - Supernova Remnants KW - X Ray Astronomy KW - Emission Spectra KW - Extragalactic Radio Sources KW - Heao 2 KW - Astrophysics KW - Supernovae-supernova remnants-X-ray observations UR - https://ui.adsabs.harvard.edu/abs/1992ChA&A..16..278W N2 - 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. DO - 10.1016/0275-1062(92)90067-L SN - 0275-1062 ER - TY - CONF TI - The Detection of Pulsed X-Ray Emission from a Nearby Radio Pulsar AU - Yancopoulos, S. AU - Helfand, D. J. AU - Hamilton, T. T. AU - Halpern, J. P. AU - Seward, F. D. AU - Becker, R. H. JO - American Astronomical Society Meeting Abstracts VL - 181 Y1 - 1992/09/1 SP - 60.05 UR - https://ui.adsabs.harvard.edu/abs/1992AAS...181.6005Y ER - TY - CONF TI - SNRs MSH 15-56 and CTA 1 AU - Wang, Z. -R. AU - Qu, Q. -Y. AU - Seward, F. JO - Frontiers Science Series Y1 - 1992/01/1 SP - 395 UR - https://ui.adsabs.harvard.edu/abs/1992fxra.conf..395W ER - TY - JOUR TI - SNRs MSH 15-56 and CTA 1. AU - Wang, Z. AU - Qu, Q. AU - Seward, F. JO - Acta Astrophysica Sinica VL - 12 Y1 - 1992/01/1 SP - 101 EP - 106 UR - https://ui.adsabs.harvard.edu/abs/1992AcApS..12..101W SN - 0253-2379 ER - TY - JOUR TI - A Large Radio Galaxy Behind the Supernova Remnant HB9 AU - Seward, F. D. AU - Fabricant, D. G. AU - Kirshner, R. P. AU - McClintock, J. E. AU - Smith, R. C. AU - Remillard, R. A. AD - 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) JO - The Astronomical Journal VL - 102 Y1 - 1991/12/1 SP - 2047 KW - Radio Galaxies KW - Supernova Remnants KW - Extragalactic Radio Sources KW - Galactic Clusters KW - X Ray Sources KW - Astrophysics KW - RADIO SOURCES: GALAXIES KW - NEBULAE: SUPERNOVA REMNANTS UR - https://ui.adsabs.harvard.edu/abs/1991AJ....102.2047S N2 - 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. PB - IOP DO - 10.1086/116027 SN - 0004-6256 ER - TY - CONF TI - FeLiX: An X-Ray Telescope to Perform a Medium Angular Resolution All-Sky Survey in the 2-10 keV Band AU - Slane, P. AU - Elvis, M. AU - Fabbiano, G. AU - Hughes, J. AU - Seward, F. AU - Szentgyorgyi, A. AU - Worrall, D. JO - Bulletin of the American Astronomical Society VL - 23 Y1 - 1991/09/1 SP - 1452 UR - https://ui.adsabs.harvard.edu/abs/1991BAAS...23.1452S ER - TY - JOUR TI - The Einstein Objective Grating Spectrometer Survey of Galactic Binary X-Ray Sources AU - Vrtilek, S. D. AU - McClintock, J. E. AU - Seward, F. D. AU - Kahn, S. M. AU - Wargelin, B. J. AD - 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) JO - The Astrophysical Journal Supplement Series VL - 76 Y1 - 1991/08/1 SP - 1127 KW - Gratings (Spectra) KW - Heao 2 KW - Proportional Counters KW - X Ray Binaries KW - X Ray Spectroscopy KW - High Resolution KW - Spectral Resolution KW - X Ray Spectra KW - Astrophysics KW - X-RAYS: BINARIES KW - X-RAYS: SPECTRA UR - https://ui.adsabs.harvard.edu/abs/1991ApJS...76.1127V N2 - 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. PB - IOP DO - 10.1086/191594 SN - 0067-0049 ER - TY - JOUR TI - G33.6+0.1: A Shell Type Supernova Remnant With Unusual Structure AU - Velusamy, T. AU - Becker, R. H. AU - Seward, F. D. AD - AA(Tata Institute of Fundamental Research, India), AB(University of California, Davis; Lawrence Livermore National Laboratory, California), AC(Smithsonian Astrophysical Observatory) JO - The Astronomical Journal VL - 102 Y1 - 1991/08/1 SP - 676 KW - Radio Sources (Astronomy) KW - Supernova Remnants KW - Very Large Array (Vla) KW - X Ray Imagery KW - Emission Spectra KW - H Ii Regions KW - Radio Astronomy KW - Radio Emission KW - Astrophysics KW - NEBULAE: SUPERNOVA REMNANTS UR - https://ui.adsabs.harvard.edu/abs/1991AJ....102..676V N2 - 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. PB - IOP DO - 10.1086/115901 SN - 0004-6256 ER - TY - CONF TI - A Large Radio Galaxy Behind the Supernova Remnant HB 9 AU - Seward, F. D. AU - Fabricant, D. G. AU - Kirshner, R. P. AU - McClintock, J. E. AU - Remillard, R. A. AU - Smith, R. C. JO - Bulletin of the American Astronomical Society VL - 23 Y1 - 1991/03/1 SP - 918 UR - https://ui.adsabs.harvard.edu/abs/1991BAAS...23..918S ER - TY - JOUR TI - Einstein Observations of Galactic Supernova Remnants AU - Seward, Frederick D. AD - AA(Harvard Smithsonian Center for Astrophysics) JO - The Astrophysical Journal Supplement Series VL - 73 Y1 - 1990/08/1 SP - 781 KW - Heao 2 KW - Milky Way Galaxy KW - Supernova Remnants KW - X Ray Sources KW - Brightness Distribution KW - Classifying KW - Image Processing KW - Proportional Counters KW - Astrophysics KW - NEBULAE: SUPERNOVA REMNANTS KW - X-RAYS: SOURCES UR - https://ui.adsabs.harvard.edu/abs/1990ApJS...73..781S N2 - 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. PB - IOP DO - 10.1086/191489 SN - 0067-0049 ER - TY - JOUR TI - A Further Study of the Molecular Cloud Associated with the Supernova Remnant G109.1-1.0 AU - Tatematsu, Ken'ichi AU - Fukui, Yasuo AU - Iwata, Takahiro AU - Seward, Frederick D. AU - Nakano, Makoto AD - AA(Nagoya University, Japan), AB(Nagoya University, Japan), AC(Nagoya University, Japan), AD(Harvard Smithsonian Center for Astrophysics), AE(Oita University, Japan) JO - The Astrophysical Journal VL - 351 Y1 - 1990/03/1 SP - 157 KW - Astronomical Spectroscopy KW - Molecular Clouds KW - Supernova Remnants KW - X Ray Sources KW - Absorption Spectra KW - Carbon Monoxide KW - Electron Transitions KW - Heao 2 KW - Particle Acceleration KW - X Ray Spectra KW - Astrophysics KW - INTERSTELLAR: MOLECULES KW - NEBULAE: INDIVIDUAL ALPHANUMERIC: G109.1-1.0 KW - NEBULAE: INDIVIDUAL ALPHANUMERIC: CTB 109 KW - NEBULAE: SUPERNOVA REMNANTS KW - X-RAYS: SOURCES KW - X-RAYS: SPECTRA UR - https://ui.adsabs.harvard.edu/abs/1990ApJ...351..157T N2 - 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. PB - IOP DO - 10.1086/168452 SN - 0004-637X ER - TY - CONF TI - Einstein Observations of Supernova Remnants AU - Seward, F. D. JO - Imaging X-Ray Astronomy. A Decade of Einstein Observatory Achievements Y1 - 1990/01/1 SP - 319 UR - https://ui.adsabs.harvard.edu/abs/1990ixra.conf..319S N2 - 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. ER - TY - CONF TI - A New Boundary for the VELA Supernova Remnant AU - Seward, F. D. JO - Imaging X-Ray Astronomy. A Decade of Einstein Observatory Achievements Y1 - 1990/01/1 SP - 241 UR - https://ui.adsabs.harvard.edu/abs/1990ixra.conf..241S N2 - 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. ER - TY - CONF TI - Distances to Galactic Supernova Remnants AU - Li, H. AU - Seward, F. D. JO - Bulletin of the American Astronomical Society VL - 21 Y1 - 1989/09/1 SP - 1203 UR - https://ui.adsabs.harvard.edu/abs/1989BAAS...21R1203L ER - TY - JOUR TI - The Crab-Like Supernova Remnants AU - Seward, Frederick D. AD - AA(Harvard Smithsonian Center for Astrophysics) JO - Space Science Reviews VL - 49 Y1 - 1989/04/1 SP - 385 EP - 423 KW - Crab Nebula KW - Neutron Stars KW - Supernova Remnants KW - Synchrotron Radiation KW - Heao 2 KW - X Ray Astronomy KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1989SSRv...49..385S N2 - 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. DO - 10.1007/BF00241871 SN - 0038-6308 ER - TY - JOUR TI - X Rays from G54.1+0.3 AU - Seward, F. D. AD - AA(Harvard Smithsonian Center for Astrophysics) JO - The Astronomical Journal VL - 97 Y1 - 1989/02/1 SP - 481 KW - Cosmic X Rays KW - Radio Sources (Astronomy) KW - Supernova Remnants KW - Absorption Spectra KW - Abundance KW - Brightness Distribution KW - Power Spectra KW - Astrophysics KW - NEBULAE: SUPERNOVA REMNANTS KW - NEBULAE: INDIVIDUAL UR - https://ui.adsabs.harvard.edu/abs/1989AJ.....97..481S N2 - 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. PB - IOP DO - 10.1086/114997 SN - 0004-6256 ER - TY - JOUR TI - A Comprehensive Study of the X-Ray Structure and Spectrum of IC 443 AU - Petre, R. AU - Szymkowiak, A. E. AU - Seward, F. D. AU - Willingale, R. AD - 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) JO - The Astrophysical Journal VL - 335 Y1 - 1988/12/1 SP - 215 KW - Astronomical Spectroscopy KW - Supernova Remnants KW - X Ray Sources KW - H Ii Regions KW - Molecular Clouds KW - Spectrophotometry KW - Stellar Envelopes KW - Astrophysics KW - NEBULAE: INDIVIDUAL ALPHANUMERIC: IC 443 KW - NEBULAE: SUPERNOVA REMNANTS KW - X-RAYS: SOURCES UR - https://ui.adsabs.harvard.edu/abs/1988ApJ...335..215P N2 - 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. PB - IOP DO - 10.1086/166922 SN - 0004-637X ER - TY - CONF TI - The Einstein Supernova Remnant Catalog AU - Seward, F. D. JO - From Einstein to AXAF, A Symposium to Celebrate the 10th Anniversary of the launch of HEAO-2, the Einstein Observatory Y1 - 1988/11/1 SP - 6 UR - https://ui.adsabs.harvard.edu/abs/1988feta.conf....6S ER - TY - CONF TI - The Vela Supernova Remnant AU - Seward, Frederick D. JO - From Einstein to AXAF, A Symposium to Celebrate the 10th Anniversary of the launch of HEAO-2, the Einstein Observatory Y1 - 1988/11/1 SP - 24 UR - https://ui.adsabs.harvard.edu/abs/1988feta.conf...24S ER - TY - JOUR TI - Pulsars, X-Ray Synchrotron Nebulae, and Guest Stars AU - Seward, Frederick D. AU - Wang, Zhen-Ru AD - AA(Harvard Smithsonian Center for Astrophysics), AB(Nanjing University, China) JO - The Astrophysical Journal VL - 332 Y1 - 1988/09/1 SP - 199 KW - Neutron Stars KW - Pulsars KW - Stellar Coronas KW - Stellar Rotation KW - Supernova Remnants KW - X Ray Astronomy KW - Charged Particles KW - Energy Dissipation KW - Magnetic Dipoles KW - Radio Sources (Astronomy) KW - Relativistic Particles KW - Astrophysics KW - NEBULAE: SUPERNOVA REMNANTS KW - PULSARS KW - RADIATION MECHANISMS KW - STARS: NEUTRON KW - STARS: ROTATION UR - https://ui.adsabs.harvard.edu/abs/1988ApJ...332..199S N2 - 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. PB - IOP DO - 10.1086/166646 SN - 0004-637X ER - TY - CONF TI - The Vela Supernova Remnant AU - Seward, F. D. JO - Bulletin of the American Astronomical Society VL - 20 Y1 - 1988/09/1 SP - 1049 UR - https://ui.adsabs.harvard.edu/abs/1988BAAS...20.1049S ER - TY - JOUR TI - Earth Rocks on Mars: Must Planetary Quarantine Be Rethought? AU - Wang, Zhen-Ru AU - Seward, F. D. AD - AA(Nanjing University, China; China Center of Advanced Science and Technology), AB(Harvard Smithsonian Center for Astrophysics) JO - Acta Astronomica Sinica VL - 29 Y1 - 1988/09/1 SP - 33 KW - Crab Nebula KW - Pulsars KW - Supernova Remnants KW - X Ray Sources KW - Photons KW - Stellar Luminosity KW - Surface Properties KW - Astronomy UR - https://ui.adsabs.harvard.edu/abs/1988AcASn..29...33W N2 - 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. SN - 0001-5245 ER - TY - JOUR TI - An X-ray investigation of crab-like supernova remnants AU - Wang, Zhen-ru AU - Seward, F. D. AD - AA(China Center of Advanced Science and Technology), AB(China Center of Advanced Science and Technology) JO - Chinese Astronomy and Astrophysics VL - 12 Y1 - 1988/09/1 SP - 212 EP - 215 UR - https://ui.adsabs.harvard.edu/abs/1988ChA&A..12..212W N2 - 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. DO - 10.1016/0275-1062(88)90049-5 SN - 0275-1062 ER - TY - CONF TI - The X-ray environment of the precursor of SN 1987A. AU - Harnden, F. R., Jr. AU - Seward, F. D. JO - Supernova 1987A in the Large Magellanic Cloud Y1 - 1988/01/1 SP - 408 EP - 410 KW - Supernova 1987A in LMC KW - Supernovae:Progenitors KW - Supernovae:X Rays KW - X Rays:Supernovae UR - https://ui.adsabs.harvard.edu/abs/1988slmc.proc..408H ER - TY - CONF TI - X-Ray Images of Supernova Remnants AU - Seward, F. D. JO - IAU Colloq. 101: Supernova Remnants and the Interstellar Medium Y1 - 1988/01/1 SP - 115 UR - https://ui.adsabs.harvard.edu/abs/1988srim.conf..115S N2 - 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. ER - TY - JOUR TI - An X-ray investigation of crab-like supernova remnants AU - Wang, Zhenru AU - Seward, F. D. AD - AA(China Center of Advanced Science and Technology; Nanjing University, China), AB(Harvard Smithsonian Center for Astrophysics) JO - Vistas in Astronomy VL - 31 Y1 - 1988/01/1 SP - 271 EP - 274 KW - Crab Nebula KW - Energy Dissipation KW - Pulsars KW - Supernova Remnants KW - X Ray Astronomy KW - Energy Transfer KW - Milky Way Galaxy KW - Morphology KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1988VA.....31..271W N2 - 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. DO - 10.1016/0083-6656(88)90210-3 SN - 0083-6656 ER - TY - CONF TI - Supernovae and supernova remnants. AU - Chevalier, Roger A. AU - Seward, Frederick D. AD - AA(University of Virginia), AB(Harvard Smithsonian Center for Astrophysics) JO - Multiwavelength Astrophysics Y1 - 1988/01/1 SP - 235 EP - 265 KW - Stellar Spectra KW - Supernova Remnants KW - Supernovae KW - Hydrogen KW - Light Curve KW - Line Spectra KW - Pulsars KW - Spectrum Analysis KW - Astrophysics KW - Pulsars:Supernovae KW - Supernova Remnants KW - Supernovae KW - Supernovae:Pulsars UR - https://ui.adsabs.harvard.edu/abs/1988mwa..work..235C N2 - 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. ER - TY - CHAP TI - An X-Ray Investigation of Crab-Like Supernova Remnants AU - Wang, Z. R. AU - Seward, F. D. JO - IAU Colloq. 108: Atmospheric Diagnostics of Stellar Evolution VL - 305 Y1 - 1988/01/1 SP - 452 UR - https://ui.adsabs.harvard.edu/abs/1988LNP...305..452W DO - 10.1007/BFb0034648 SN - 0075-8450 ER - TY - CONF TI - Survey of Column Densities to Galactic X-ray Sources Using the Einstein OGS AU - Vrtilek, S. D. AU - Wargelin, B. J. AU - McClintock, J. E. AU - Kahn, S. M. AU - Seward, F. D. JO - Bulletin of the American Astronomical Society VL - 19 Y1 - 1987/09/1 SP - 1076 UR - https://ui.adsabs.harvard.edu/abs/1987BAAS...19.1076V ER - TY - CONF TI - Neutron Stars in Twelve Supernova Remnants AU - Seward, Frederick D. AD - AA(Harvard Smithsonian Center for Astrophysics) JO - The Origin and Evolution of Neutron Stars VL - 125 Y1 - 1987/01/1 SP - 99 KW - Binary Stars KW - Neutron Stars KW - Stellar Coronas KW - Stellar Rotation KW - Supernova Remnants KW - X Ray Astronomy KW - Charged Particles KW - Gravitational Collapse KW - Magnetic Fields KW - Pulsars KW - Red Giant Stars KW - Synchrotron Radiation KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1987IAUS..125...99S N2 - 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. SN - 1743-9221 ER - TY - JOUR TI - X-Ray Emission Lines from Three Galactic Bulge Sources AU - Vrtilek, S. D. AU - Helfand, D. J. AU - Halpern, J. P. AU - Kahn, S. M. AU - Seward, F. D. AD - 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) JO - The Astrophysical Journal VL - 308 Y1 - 1986/09/1 SP - 644 KW - Astronomical Spectroscopy KW - Emission Spectra KW - Galactic Bulge KW - Globular Clusters KW - Line Spectra KW - Milky Way Galaxy KW - X Ray Binaries KW - Astronomical Models KW - Black Body Radiation KW - Bremsstrahlung KW - Galactic Structure KW - Heao 2 KW - Spaceborne Astronomy KW - Astrophysics KW - X-RAYS: BINARIES KW - X-RAYS: BURSTS UR - https://ui.adsabs.harvard.edu/abs/1986ApJ...308..644V N2 - 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. PB - IOP DO - 10.1086/164535 SN - 0004-637X ER - TY - JOUR TI - Spectral Variability of Cygnus X-2: Structure in the Circumsource Material AU - Vrtilek, S. D. AU - Kahn, S. M. AU - Grindlay, J. E. AU - Helfand, D. J. AU - Seward, F. D. AD - 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) JO - The Astrophysical Journal VL - 307 Y1 - 1986/08/1 SP - 698 KW - Stellar Spectra KW - Variable Stars KW - X Ray Binaries KW - Black Body Radiation KW - Broadband KW - Companion Stars KW - Neutron Stars KW - Spectral Energy Distribution KW - Astrophysics KW - RADIATION MECHANISMS KW - STARS: INDIVIDUAL CONSTELLATION NAME: CYGNUS X-2 KW - X-RAYS: BINARIES UR - https://ui.adsabs.harvard.edu/abs/1986ApJ...307..698V N2 - 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. PB - IOP DO - 10.1086/164455 SN - 0004-637X ER - TY - JOUR TI - A 6 Second Periodic X-Ray Source in Carina AU - Seward, F. D. AU - Charles, P. A. AU - Smale, A. P. AD - AA(Harvard Smithsonian Center for Astrophysics), AB(University of Oxford, UK) JO - The Astrophysical Journal VL - 305 Y1 - 1986/06/1 SP - 814 KW - B Stars KW - Variable Stars KW - X Ray Binaries KW - Exosat Satellite KW - X Ray Spectra KW - Astrophysics KW - STARS: BE KW - STARS: INDIVIDUAL ALPHANUMERIC: 1E 1048.1-5937 KW - X-RAYS: BINARIES KW - X-RAYS: SOURCES UR - https://ui.adsabs.harvard.edu/abs/1986ApJ...305..814S N2 - 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. PB - IOP DO - 10.1086/164294 SN - 0004-637X ER - TY - JOUR TI - Neutron Stars in Supernova Remnants AU - Seward, F. D. AD - AA(Harvard Smithsonian Center for Astrophysics) JO - Sky and Telescope VL - 71 Y1 - 1986/01/1 SP - 6 KW - Magellanic Clouds KW - Neutron Stars KW - Supernova Remnants KW - X Ray Spectra KW - Interstellar Matter KW - Nebulae KW - Pulsars KW - Stellar Magnetic Fields KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1986S&T....71....6S N2 - 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. SN - 0037-6604 ER - TY - JOUR TI - An Upper Limit to X-Ray Emission from Saturn AU - Gilman, D. A. AU - Hurley, K. C. AU - Seward, F. D. AU - Schnopper, H. W. AU - Sullivan, J. D. AU - Metzger, A. E. AD - 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) JO - The Astrophysical Journal VL - 300 Y1 - 1986/01/1 SP - 453 KW - Auroral Arcs KW - Heao 2 KW - Planetary Radiation KW - Saturn (Planet) KW - Saturn Atmosphere KW - X Ray Sources KW - Bremsstrahlung KW - Energy Transfer KW - Pioneer 11 Space Probe KW - Planetary Magnetospheres KW - Ultraviolet Astronomy KW - X Ray Spectra KW - SATURN KW - X-RAYS KW - EMISSIONS KW - MAGNETOSPHERE KW - PIONEER 11 KW - ULTRAVIOLET KW - WAVELENGTHS KW - VOYAGER MISSIONS KW - SPACECRAFT OBSERVATIONS KW - SOURCE KW - Lunar and Planetary Exploration; Saturn KW - PLANETS: SATURN KW - X-RAYS: SOURCES UR - https://ui.adsabs.harvard.edu/abs/1986ApJ...300..453G N2 - 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. PB - IOP DO - 10.1086/163820 SN - 0004-637X ER - TY - JOUR TI - EINSTEIN observations of the VELA supernova remnant : the spatial structure of the hot emitting gas. AU - Kahn, S. M. AU - Gorenstein, P. AU - Harnden, F. R., Jr. AU - Seward, F. D. AD - AA(University of California, Berkeley), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics) JO - The Astrophysical Journal VL - 299 Y1 - 1985/12/1 SP - 821 EP - 827 KW - Heao 2 KW - Nebulae KW - Supernova Remnants KW - X Ray Sources KW - X Ray Spectra KW - Spectrum Analysis KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1985ApJ...299..821K N2 - 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. PB - IOP DO - 10.1086/163748 SN - 0004-637X ER - TY - JOUR TI - Einstein observations of VELA X and the VELA pulsar. AU - Harnden, F. R., Jr. AU - Grant, P. D. AU - Seward, F. D. AU - Kahn, S. M. AD - AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics), AD(University of California, Berkeley) JO - The Astrophysical Journal VL - 299 Y1 - 1985/12/1 SP - 828 EP - 838 KW - Heao 2 KW - Nebulae KW - Neutron Stars KW - Pulsars KW - Supernova Remnants KW - X Ray Sources KW - Morphology KW - Stellar Temperature KW - Surface Temperature KW - Thermal Emission KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1985ApJ...299..828H N2 - 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. PB - IOP DO - 10.1086/163749 SN - 0004-637X ER - TY - JOUR TI - X-ray observations of the supernova remnant W 44. AU - Smith, A. AU - Jones, L. R. AU - Watson, M. G. AU - Willingale, R. AU - Wood, N. AU - Seward, F. D. AD - 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) JO - Monthly Notices of the Royal Astronomical Society VL - 217 Y1 - 1985/11/1 SP - 99 EP - 104 KW - Astronomical Models KW - Radio Sources (Astronomy) KW - Supernova Remnants KW - X Ray Sources KW - Heao 2 KW - Interstellar Matter KW - Molecular Clouds KW - Plasma Temperature KW - X Ray Spectra KW - Astronomy UR - https://ui.adsabs.harvard.edu/abs/1985MNRAS.217...99S N2 - 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. PB - OUP DO - 10.1093/mnras/217.1.99 SN - 0035-8711 ER - TY - CONF TI - The X-Ray Structure and Spectrum of IC 443 AU - Petre, R. AU - Szymkowiak, A. E. AU - Seward, F. D. AU - Canizares, C. R. AU - Willingale, R. AU - Rolf, D. AU - Woods, N. JO - Bulletin of the American Astronomical Society VL - 17 Y1 - 1985/09/1 SP - 883 UR - https://ui.adsabs.harvard.edu/abs/1985BAAS...17..883P ER - TY - JOUR TI - Young supernova remnants. AU - Seward, F. D. AU - Gorenstein, P. AU - Tucker, W. H. AD - AA(Smithsonian Astrophysical Observatory), AB(Smithsonian Astrophysical Observatory), AC(Smithsonian Astrophysical Observatory; University of California, Irvine) JO - Scientific American VL - 253 Y1 - 1985/08/1 SP - 88 EP - 96 KW - Heao 2 KW - Pulsars KW - Stellar Mass Accretion KW - Supernova Remnants KW - X Ray Sources KW - X Ray Telescopes KW - Crab Nebula KW - Events KW - Radio Astronomy KW - Shock Waves KW - Star Clusters KW - Synchrotron Radiation KW - Astrophysics KW - Pulsars:Supernova Remnants KW - Supernova Remnants:Pulsars KW - Supernova Remnants:X-Ray Sources KW - X-Ray Sources:Supernova Remnants UR - https://ui.adsabs.harvard.edu/abs/1985SciAm.253b..88S N2 - 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. DO - 10.1038/scientificamerican0885-88 SN - 0036-8733 ER - TY - JOUR TI - Supernova remnants containing neutron stars. AU - Seward, F. D. AD - AA(Harvard Smithsonian Center for Astrophysics) JO - Comments on Astrophysics VL - 11 Y1 - 1985/08/1 SP - 15 EP - 51 KW - Neutron Stars KW - Supernova Remnants KW - X Ray Astronomy KW - Binary Stars KW - Crab Nebula KW - Gravitational Collapse KW - Pulsars KW - Radio Sources (Astronomy) KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1985ComAp..11...15S N2 - 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. SN - 0146-2970 ER - TY - JOUR TI - 1E 1048.1-5937 AU - Smale, A. P. AU - Charles, P. A. AU - Corbet, R. H. D. AU - Seward, F. D. JO - International Astronomical Union Circular VL - 4083 Y1 - 1985/07/1 SP - 3 UR - https://ui.adsabs.harvard.edu/abs/1985IAUC.4083....3S N2 - 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." SN - 0081-0304 ER - TY - CONF TI - High-Resolution X-ray Spectroscopy of Three Galactic Bulge Sources AU - Vrtilek, S. D. AU - Chanan, G. A. AU - Helfand, D. J. AU - Kahn, S. M. AU - Seward, F. D. JO - Bulletin of the American Astronomical Society VL - 17 Y1 - 1985/03/1 SP - 590 UR - https://ui.adsabs.harvard.edu/abs/1985BAAS...17..590V ER - TY - CONF TI - The X-ray morphology of the Vela X region. AU - Harnden, F. R., Jr. AU - Grant, P. D. AU - Seward, F. D. AD - AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics) JO - The Crab Nebula and Related Supernova Remnants Y1 - 1985/01/1 SP - 203 EP - 209 KW - Emission Spectra KW - Pulsars KW - Radio Sources (Astronomy) KW - Spectral Energy Distribution KW - Supernova Remnants KW - X Ray Spectra KW - Brightness Distribution KW - Diffuse Radiation KW - Heao 2 KW - Point Sources KW - Spaceborne Astronomy KW - Spectrum Analysis KW - Astrophysics KW - Pulsars:Supernova Remnants KW - Supernova Remnants:Pulsars KW - Supernova Remnants:X-Ray Maps KW - X-Ray Maps:Supernova Remnants UR - https://ui.adsabs.harvard.edu/abs/1985cnrs.work..203H N2 - 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. ER - TY - JOUR TI - A new fast X-ray pulsar. AU - Seward, F. D. JO - Physics Today VL - 38 Y1 - 1985/01/1 SP - S8 KW - X-Ray Pulsars UR - https://ui.adsabs.harvard.edu/abs/1985PhT....38R...8S SN - 0031-9228 ER - TY - CONF TI - Discovery of a 50 msec pulsar in the Large Magellanic Cloud. AU - Seward, F. D. AU - Harnden, F. R., Jr. AU - Helfand, D. J. JO - X-ray Astronomy 1984 Y1 - 1985/01/1 SP - 297 EP - 300 KW - Magellanic Clouds:X-Ray Pulsars KW - X-Ray Pulsars:Magellanic Clouds UR - https://ui.adsabs.harvard.edu/abs/1985xra..conf..297S N2 - 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. ER - TY - CONF TI - The 50 millisecond pulsar in the Large Magellanic Cloud and the X-raypulse emission mechanism. AU - Seward, F. D. AU - Harnden, F. R., Jr. AU - Elsner, R. F. AD - AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(NASA Marshall Space Flight Center) JO - The Crab Nebula and Related Supernova Remnants Y1 - 1985/01/1 SP - 165 EP - 171 KW - Emission Spectra KW - Magellanic Clouds KW - Pulsars KW - Stellar Physics KW - Supernova Remnants KW - X Ray Spectra KW - Crab Nebula KW - Spectral Energy Distribution KW - Stellar Luminosity KW - Stellar Spectrophotometry KW - Synchrotron Radiation KW - Astrophysics KW - Magellanic Clouds:Pulsars KW - Pulsars:Magellanic Clouds KW - Pulsars:Supernova Remnants KW - Supernova Remnants:Pulsars KW - X-Ray Luminosities:X-Ray Pulsars KW - X-Ray Pulsars:X-Ray Luminosities UR - https://ui.adsabs.harvard.edu/abs/1985cnrs.work..165S N2 - 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. ER - TY - JOUR TI - Discovery of a 50 millisecond pulsar in the Large Magellanic Cloud. AU - Seward, F. D. AU - Harnden, F. R., Jr. AU - Helfand, D. J. AD - AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Columbia University, New York) JO - The Astrophysical Journal VL - 287 Y1 - 1984/12/1 SP - L19 EP - L22 KW - Magellanic Clouds KW - Pulsars KW - Supernova Remnants KW - X Ray Sources KW - Crab Nebula KW - Galactic Radiation KW - Nebulae KW - Pulse Duration KW - Pulsed Radiation KW - Astronomy KW - Magellanic Clouds:Supernova Remnants KW - Magellanic Clouds:X-Ray Pulsars KW - Supernova Remnants:Magellanic Clouds KW - Supernova Remnants:X-Ray Pulsars KW - X-Ray Pulsars:Magellanic Clouds KW - X-Ray Pulsars:Supernova Remnants UR - https://ui.adsabs.harvard.edu/abs/1984ApJ...287L..19S N2 - 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. PB - IOP DO - 10.1086/184388 SN - 0004-637X ER - TY - JOUR TI - 2S 0142+61 AU - Seward, F. JO - International Astronomical Union Circular VL - 4001 Y1 - 1984/10/1 SP - 2 UR - https://ui.adsabs.harvard.edu/abs/1984IAUC.4001....2S N2 - 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." SN - 0081-0304 ER - TY - JOUR TI - An X-ray investigation of the unusual supernova remnant CTB 80. AU - Wang, Z. R. AU - Seward, F. D. AD - AA(Nanjing University, China; Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics) JO - The Astrophysical Journal VL - 285 Y1 - 1984/10/1 SP - 607 EP - 612 KW - Nebulae KW - Satellite Observation KW - Supernova Remnants KW - X Ray Astronomy KW - X Ray Sources KW - Astronomical Maps KW - Luminosity KW - X Ray Imagery KW - Astronomy UR - https://ui.adsabs.harvard.edu/abs/1984ApJ...285..607W N2 - 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. PB - IOP DO - 10.1086/162536 SN - 0004-637X ER - TY - CONF TI - A Six-Second Periodic X-ray Source in Carina AU - Seward, F. D. AU - Charles, P. A. JO - Bulletin of the American Astronomical Society VL - 16 Y1 - 1984/09/1 SP - 983 UR - https://ui.adsabs.harvard.edu/abs/1984BAAS...16Q.983S ER - TY - JOUR TI - Einstein observations of the Crab Nebula pulsar. AU - Harnden, F. R., Jr. AU - Seward, F. D. AD - AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics) JO - The Astrophysical Journal VL - 283 Y1 - 1984/08/1 SP - 279 EP - 285 KW - Crab Nebula KW - Pulsars KW - X Ray Sources KW - Heao 2 KW - Light Curve KW - Spatial Distribution KW - Temporal Distribution KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1984ApJ...283..279H N2 - 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. PB - IOP DO - 10.1086/162304 SN - 0004-637X ER - TY - JOUR TI - High-resolution soft X-ray spectra of Scorpius X-1 : the structure ofcircumsource accreting material. AU - Kahn, S. M. AU - Seward, F. D. AU - Chlebowski, T. AD - 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) JO - The Astrophysical Journal VL - 283 Y1 - 1984/08/1 SP - 286 EP - 294 KW - Binary Stars KW - Stellar Mass Accretion KW - Stellar Spectra KW - X Ray Stars KW - Abundance KW - Calibrating KW - High Resolution KW - Spectrum Analysis KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1984ApJ...283..286K N2 - 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. PB - IOP DO - 10.1086/162305 SN - 0004-637X ER - TY - JOUR TI - X-rays from eta Carinae. AU - Chlebowski, T. AU - Seward, F. D. AU - Swank, J. AU - Szymkowiak, A. AD - 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) JO - The Astrophysical Journal VL - 281 Y1 - 1984/06/1 SP - 665 EP - 672 KW - Nebulae KW - Stellar Envelopes KW - Variable Stars KW - X Ray Sources KW - Astronomical Maps KW - Morphology KW - Spectral Energy Distribution KW - Stellar Models KW - X Ray Spectroscopy KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1984ApJ...281..665C N2 - 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). PB - IOP DO - 10.1086/162143 SN - 0004-637X ER - TY - JOUR TI - The X-ray nebula around PSR 1509-58. AU - Seward, F. D. AU - Harnden, F. R., Jr. AU - Szymkowiak, A. AU - Swank, J. AD - 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) JO - The Astrophysical Journal VL - 281 Y1 - 1984/06/1 SP - 650 EP - 657 KW - Nebulae KW - Pulsars KW - Supernova Remnants KW - Synchrotron Radiation KW - X Ray Sources KW - Crab Nebula KW - Luminosity KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1984ApJ...281..650S N2 - 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. PB - IOP DO - 10.1086/162141 SN - 0004-637X ER - TY - JOUR TI - Radio and X-ray maps of the supernova remnant W 49B. AU - Pye, J. P. AU - Becker, R. H. AU - Seward, F. D. AU - Thomas, N. AD - AA(University of Leicester, UK), AB(University of Leicester, UK), AC(Virginia Polytechnic Institute and State University), AD(Harvard Smithsonian Center for Astrophysics) JO - Monthly Notices of the Royal Astronomical Society VL - 207 Y1 - 1984/04/1 SP - 649 EP - 657 KW - Astronomical Maps KW - Radio Sources (Astronomy) KW - Supernova Remnants KW - X Ray Sources KW - Brightness Distribution KW - Centimeter Waves KW - Spaceborne Astronomy KW - Spatial Distribution KW - Astronomy UR - https://ui.adsabs.harvard.edu/abs/1984MNRAS.207..649P N2 - 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. PB - OUP DO - 10.1093/mnras/207.3.649 SN - 0035-8711 ER - TY - JOUR TI - X-rays from the SNR 3C 391. AU - Wang, Z. R. AU - Seward, F. D. AD - AA(Harvard Smithsonian Center for Astrophysics) JO - The Astrophysical Journal VL - 279 Y1 - 1984/04/1 SP - 705 EP - 707 KW - Supernova Remnants KW - X Ray Sources KW - Heao 2 KW - Luminosity KW - Radio Sources (Astronomy) KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1984ApJ...279..705W N2 - 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. PB - IOP DO - 10.1086/161935 SN - 0004-637X ER - TY - CONF TI - Period Behavior of the New LMC Pulsar AU - Harnden, F. R., Jr. AU - Seward, F. D. JO - Bulletin of the American Astronomical Society VL - 16 Y1 - 1984/03/1 SP - 542 UR - https://ui.adsabs.harvard.edu/abs/1984BAAS...16..542H ER - TY - CONF TI - Dramatic Variability in the X-Ray Flux of Hercules X-1 Preceding the Binary Eclipse AU - Vrtilek, S. D. AU - Kahn, S. M. AU - Seward, F. D. AU - Grindlay, J. E. JO - Bulletin of the American Astronomical Society VL - 16 Y1 - 1984/03/1 SP - 471 UR - https://ui.adsabs.harvard.edu/abs/1984BAAS...16..471V ER - TY - JOUR TI - X-Ray Pulsar in Large Magellanic Cloud AU - Seward, F. D. AU - Harnden, F. R., Jr. AU - Helfand, D. JO - International Astronomical Union Circular VL - 3928 Y1 - 1984/03/1 SP - 2 UR - https://ui.adsabs.harvard.edu/abs/1984IAUC.3928....2S N2 - 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. SN - 0081-0304 ER - TY - CONF TI - A 50-Millisecond Crab-like Pulsar in the Large Magellanic Cloud AU - Seward, F. D. AU - Harnden, F. R., Jr. AU - Helfand, D. J. JO - Bulletin of the American Astronomical Society VL - 16 Y1 - 1984/03/1 SP - 542 UR - https://ui.adsabs.harvard.edu/abs/1984BAAS...16..542S ER - TY - JOUR TI - The central X-ray source in SS 433. AU - Grindlay, J. E. AU - Band, D. AU - Seward, F. AU - Leahy, D. AU - Weisskopf, M. C. AU - Marshall, F. E. AD - 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) JO - The Astrophysical Journal VL - 277 Y1 - 1984/02/1 SP - 286 EP - 295 KW - Binary Stars KW - Black Holes (Astronomy) KW - X Ray Sources KW - Accretion Disks KW - Angular Momentum KW - Bremsstrahlung KW - Companion Stars KW - Heao 2 KW - Stellar Flares KW - Stellar Luminosity KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1984ApJ...277..286G N2 - 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. PB - IOP DO - 10.1086/161695 SN - 0004-637X ER - TY - JOUR TI - The high resolution soft X-ray spectrum of AM Herculis. AU - Heise, J. AU - Kruszewski, A. AU - Chlebowski, T. AU - Mewe, R. AU - Kahn, S. AU - Seward, F. D. AD - 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) JO - Physica Scripta Volume T VL - 7 Y1 - 1984/01/1 SP - 115 EP - 117 KW - Binary Stars KW - Light Curve KW - Magnetic Stars KW - White Dwarf Stars KW - X Ray Spectra KW - Black Body Radiation KW - Heao 2 KW - Ultraviolet Radiation KW - Astrophysics KW - AM Herculis:X-Ray Spectra KW - X-Ray Spectra:AM Herculis UR - https://ui.adsabs.harvard.edu/abs/1984PhST....7..115H N2 - 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. DO - 10.1088/0031-8949/1984/T7/026 SN - 0031-89490281-1847 ER - TY - JOUR TI - A new Crab-like pulsar in the Large Magellanic Cloud. AU - Helfand, D. J. AU - Seward, F. D. AU - Harnden, F. R. JO - News Letter of the Astronomical Society of New York VL - 2 Y1 - 1984/01/1 SP - 7 EP - 8 KW - Magellanic Clouds:Pulsars KW - Period Changes:Pulsars KW - Pulsars:Magellanic Clouds KW - Pulsars:Period Changes KW - Pulsars:X Rays KW - X Rays:Pulsars UR - https://ui.adsabs.harvard.edu/abs/1984ASNYN...2....7H SN - 0148-9992 ER - TY - JOUR TI - Book-Review - Superstars AU - Clark, D. H. AU - Seward, F. D. JO - Sky and Telescope VL - 68 Y1 - 1984/01/1 SP - 324 UR - https://ui.adsabs.harvard.edu/abs/1984S&T....68..324C SN - 0037-6604 ER - TY - JOUR TI - The X-ray emission of the old Nova V603 Aquilae (1918). AU - Drechsel, H. AU - Rahe, J. AU - Wargau, W. AU - Seward, F. D. AU - Wang, Z. R. AD - 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) JO - Astronomy and Astrophysics VL - 126 Y1 - 1983/10/1 SP - 357 EP - 362 KW - Astronomical Spectroscopy KW - Emission Spectra KW - Light Curve KW - Novae KW - Spaceborne Astronomy KW - X Ray Sources KW - Astronomical Photometry KW - Stellar Mass Accretion KW - White Dwarf Stars KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1983A&A...126..357D N2 - 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. SN - 0004-6361 ER - TY - JOUR TI - The X-ray lobes of SS 433. AU - Watson, M. G. AU - Willingale, R. AU - Grindlay, J. E. AU - Seward, F. D. AD - AA(University of Leicester, UK), AB(University of Leicester, UK), AC(Harvard Smithsonian Center for Astrophysics), AD(Harvard Smithsonian Center for Astrophysics) JO - The Astrophysical Journal VL - 273 Y1 - 1983/10/1 SP - 688 EP - 696 KW - Binary Stars KW - Stellar Spectrophotometry KW - Stellar Structure KW - X Ray Sources KW - Astronomical Maps KW - Emission Spectra KW - Heao 2 KW - Line Spectra KW - Spectrum Analysis KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1983ApJ...273..688W N2 - 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. PB - IOP DO - 10.1086/161403 SN - 0004-637X ER - TY - JOUR TI - The detection of x rays from Jupiter AU - Metzger, Albert E. AU - Luthey, Joe L. AU - Gilman, David A. AU - Hurley, Kevin C. AU - Schnopper, Herbert W. AU - Seward, Frederick D. AU - Sullivan, James D. AD - 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) JO - Journal of Geophysical Research VL - 88 Y1 - 1983/10/1 SP - 7731 EP - 7741 KW - Heao 2 KW - Jupiter Atmosphere KW - Planetary Radiation KW - X Rays KW - Auroral Zones KW - Energy Spectra KW - Oxygen Ions KW - Planetary Magnetospheres KW - Polar Regions KW - Radiant Flux Density KW - Sulfur KW - JUPITER KW - X-RAYS KW - ENERGY KW - POLAR REGIONS KW - OBSERVATIONS KW - ASTRONOMY KW - FLUX KW - IMAGERY KW - DENSITY KW - LUMINOSITY KW - SPECTRA KW - CHARACTERISTICS KW - EMISSIONS KW - IPC KW - AURORAS KW - EINSTEIN X-RAY ASTRONOMY SATELLITE KW - IMAGING PROPORTIONAL COUNTER UR - https://ui.adsabs.harvard.edu/abs/1983JGR....88.7731M N2 - 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. DO - 10.1029/JA088iA10p07731 SN - 0148-0227 ER - TY - CONF TI - An X-Ray Investigation of the Unusual Supernova Remnant CTB80 AU - Wang, Z. R. AU - Seward, F. D. JO - Bulletin of the American Astronomical Society VL - 15 Y1 - 1983/09/1 SP - 953 UR - https://ui.adsabs.harvard.edu/abs/1983BAAS...15..953W ER - TY - JOUR TI - The period history of the X-ray pulsar in MSH 15-52. AU - Weisskopf, M. C. AU - Elsner, R. F. AU - Darbo, W. AU - Leahy, D. AU - Naranan, S. AU - Sutherland, P. G. AU - Grindlay, J. E. AU - Harnden, F. R., Jr. AU - Seward, F. D. AD - 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) JO - The Astrophysical Journal VL - 267 Y1 - 1983/04/1 SP - 711 EP - 712 KW - Periodic Variations KW - Pulsars KW - Pulse Duration KW - Supernova Remnants KW - X Ray Sources KW - Cross Correlation KW - Light Curve KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1983ApJ...267..711W N2 - 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. PB - IOP DO - 10.1086/160908 SN - 0004-637X ER - TY - JOUR TI - MSH 15-52 : a supernova remnant containing two compact X-ray sources. AU - Seward, F. D. AU - Harnden, F. R., Jr. AU - Murdin, P. AU - Clark, D. H. AD - AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Royal Greenwich Observatory), AD(Rutherford Appleton Laboratory) JO - The Astrophysical Journal VL - 267 Y1 - 1983/04/1 SP - 698 EP - 710 KW - Nebulae KW - Pulsars KW - Radio Sources (Astronomy) KW - Supernova Remnants KW - X Ray Sources KW - Emission Spectra KW - H Alpha Line KW - Heao 2 KW - Infrared Spectra KW - Interstellar Gas KW - Shock Wave Interaction KW - Stellar Evolution KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1983ApJ...267..698S N2 - 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. PB - IOP DO - 10.1086/160907 SN - 0004-637X ER - TY - CONF TI - X-Rays from the SNR 3C391 AU - Wang, Z. R. AU - Seward, F. D. JO - Bulletin of the American Astronomical Society VL - 15 Y1 - 1983/03/1 SP - 637 UR - https://ui.adsabs.harvard.edu/abs/1983BAAS...15..637W ER - TY - CONF TI - Einstein OGS/MPC Observations of Cygnus X-2 AU - Vrtilek, S. Dil AU - Kahn, S. M. AU - Seward, F. D. AU - Grindlay, J. E. JO - Bulletin of the American Astronomical Society VL - 15 Y1 - 1983/03/1 SP - 636 UR - https://ui.adsabs.harvard.edu/abs/1983BAAS...15..636V ER - TY - JOUR TI - The mass of Tycho's supernova remnant as determined from a high-resolution X-ray map. AU - Seward, F. AU - Gorenstein, P. AU - Tucker, W. AD - AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics) JO - The Astrophysical Journal VL - 266 Y1 - 1983/03/1 SP - 287 EP - 297 KW - Astronomical Maps KW - Interstellar Matter KW - Nebulae KW - Stellar Mass KW - Supernova Remnants KW - X Ray Sources KW - Astronomical Models KW - Ejecta KW - Heao 2 KW - High Resolution KW - Mass Distribution KW - Shock Waves KW - X Ray Imagery KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1983ApJ...266..287S N2 - 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. PB - IOP DO - 10.1086/160778 SN - 0004-637X ER - TY - JOUR TI - TYCHO Kepler and Einstein / Supernova Remnants AU - Reid, P. AU - Seward, F. AU - White, R. L. AU - Long, K. S. AU - Dennefeld, M. AU - Leibowitz, E. M. AU - Danziger, I. J. JO - Sky and Telescope VL - 65 Y1 - 1983/03/1 SP - 223 UR - https://ui.adsabs.harvard.edu/abs/1983S&T....65..223R SN - 0037-6604 ER - TY - CONF TI - High resolution X-ray images of Puppis A and IC 443 AU - Petre, R. AU - Winkler, P. F. AU - Seward, F. D. AU - Willingale, R. AU - Rolf, D. AU - Woods, N. AU - Canizares, C. R. AD - 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) JO - Supernova Remnants and their X-ray Emission VL - 101 Y1 - 1983/01/1 SP - 289 EP - 293 KW - Astronomical Spectroscopy KW - High Resolution KW - Spatial Distribution KW - Supernova Remnants KW - X Ray Astronomy KW - Brightness Distribution KW - Brightness Temperature KW - Interstellar Matter KW - Molecular Clouds KW - Spectral Resolution KW - X Ray Imagery KW - Astronomy UR - https://ui.adsabs.harvard.edu/abs/1983IAUS..101..289P N2 - 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. SN - 1743-9221 ER - TY - CONF TI - X-ray studies of SS433 AU - Grindlay, J. E. AU - Band, D. AU - Seward, F. AU - Stella, L. AU - Watson, M. AD - 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) JO - Supernova Remnants and their X-ray Emission VL - 101 Y1 - 1983/01/1 SP - 459 EP - 463 KW - Eclipsing Binary Stars KW - Stellar Models KW - X Ray Astronomy KW - X Ray Sources KW - Astronomical Maps KW - B Stars KW - Black Holes (Astronomy) KW - Heao 2 KW - Kinetic Energy KW - Plasma Jets KW - Relativistic Plasmas KW - Stellar Mass Accretion KW - Synchrotron Radiation KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1983IAUS..101..459G N2 - 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). SN - 1743-9221 ER - TY - JOUR TI - Discovery of a New Pulsar Within a Supernova Remnant AU - Seward, F. D. AU - Harnden, F. R., Jr. JO - Mercury VL - 12 Y1 - 1983/01/1 SP - 56 UR - https://ui.adsabs.harvard.edu/abs/1983Mercu..12...56S SN - 0047-6773 ER - TY - CONF TI - The mass and structure of the remnant of Tycho's supernova AU - Gorenstein, P. AU - Seward, F. AU - Tucker, W. AD - AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(Harvard Smithsonian Center for Astrophysics) JO - Supernova Remnants and their X-ray Emission VL - 101 Y1 - 1983/01/1 SP - 1 EP - 15 KW - Ejecta KW - Interstellar Matter KW - Mass Distribution KW - Supernova Remnants KW - X Ray Sources KW - Astronomical Maps KW - High Resolution KW - Neutron Stars KW - Radii KW - Shock Heating KW - Stellar Mass Ejection KW - Surface Temperature KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1983IAUS..101....1G N2 - 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. SN - 1743-9221 ER - TY - CONF TI - Supernova remnants with compact X-ray sources AU - Seward, F. D. AU - Harnden, F. R., Jr. AU - Murdin, P. G. AU - Wood, R. AU - Gilmozzi, R. AU - Clark, D. H. AU - Danziger, I. J. AU - Furr, A. W. AD - 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) JO - Supernova Remnants and their X-ray Emission VL - 101 Y1 - 1983/01/1 SP - 417 EP - 419 KW - Astronomical Spectroscopy KW - Crab Nebula KW - Pulsars KW - Supernova Remnants KW - X Ray Sources KW - Infrared Spectra KW - Radial Velocity KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1983IAUS..101..417S N2 - 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. SN - 1743-9221 ER - TY - CONF TI - The X-ray structure of the supernova remnant G78.2 + 2.1 AU - Higgs, L. A. AU - Landecker, T. L. AU - Seward, F. D. AD - AA(Dominion Radio Astrophysical Observatory), AB(Dominion Radio Astrophysical Observatory), AC(Harvard Smithsonian Center for Astrophysics) JO - Supernova Remnants and their X-ray Emission VL - 101 Y1 - 1983/01/1 SP - 281 EP - 286 KW - Supernova Remnants KW - X Ray Sources KW - Luminosity KW - Nebulae KW - Radio Emission KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1983IAUS..101..281H N2 - 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. SN - 1743-9221 ER - TY - CONF TI - Einstein observations of the SNRs IC443, W44 and W49B AU - Watson, M. G. AU - Willingale, R. AU - Pye, J. P. AU - Rolf, D. P. AU - Wood, N. AU - Thomas, N. AU - Seward, F. D. AD - 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) JO - Supernova Remnants and their X-ray Emission VL - 101 Y1 - 1983/01/1 SP - 273 EP - 280 KW - Molecular Clouds KW - Molecular Spectra KW - Supernova Remnants KW - X Ray Astronomy KW - X Ray Imagery KW - Abundance KW - Electron Density (Concentration) KW - Heao 2 KW - Limb Brightening KW - Stellar Luminosity KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1983IAUS..101..273W N2 - 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. SN - 1743-9221 ER - TY - CONF TI - An X-ray halo around Cassiopeia A AU - Stewart, G. C. AU - Fabian, A. C. AU - Seward, F. D. AD - AA(University of Cambridge, UK), AB(University of Cambridge, UK), AC(Harvard Smithsonian Center for Astrophysics) JO - Supernova Remnants and their X-ray Emission VL - 101 Y1 - 1983/01/1 SP - 59 EP - 64 KW - Astronomical Spectroscopy KW - Cassiopeia A KW - Emission Spectra KW - Supernova Remnants KW - X Ray Sources KW - Brightness Distribution KW - H Ii Regions KW - Halos KW - Spectral Energy Distribution KW - Visible Spectrum KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1983IAUS..101...59S N2 - 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. SN - 1743-9221 ER - TY - JOUR TI - Röntgen-Messungen von V 603 Aquilae AU - Drechsel, H. AU - Rahe, J. AU - Wargau, W. AU - Seward, F. AU - Wang, Z. JO - Mitteilungen der Astronomischen Gesellschaft Hamburg VL - 60 Y1 - 1983/01/1 SP - 357 UR - https://ui.adsabs.harvard.edu/abs/1983MitAG..60..357D SN - 0374-1958 ER - TY - CONF TI - Supernova remnants with central pulsars AU - Seward, F. D. AD - AA(Harvard Smithsonian Center for Astrophysics; University of Cambridge, UK) JO - Supernova Remnants and their X-ray Emission VL - 101 Y1 - 1983/01/1 SP - 405 EP - 416 KW - Pulsars KW - Supernova Remnants KW - X Ray Sources KW - Astronomical Models KW - Crab Nebula KW - Synchrotron Radiation KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1983IAUS..101..405S N2 - 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. SN - 1743-9221 ER - TY - CONF TI - Einstein observations of supernova remnants AU - Seward, F. D. AD - AA(Harvard Smithsonian Center for Astrophysics) JO - Supernovae: A Survey of Current Research VL - 90 Y1 - 1982/11/1 SP - 519 EP - 528 KW - Galactic Radiation KW - Heao 2 KW - Stellar Evolution KW - Supernova Remnants KW - X Ray Imagery KW - X Ray Sources KW - Astronomical Maps KW - Crab Nebula KW - Diffuse Radiation KW - Ejecta KW - Interstellar Matter KW - Astronomy UR - https://ui.adsabs.harvard.edu/abs/1982ASIC...90..519S N2 - 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. DO - 10.1007/978-94-009-7876-8_32 ER - TY - JOUR TI - X-ray structure of the SNR G78.2+2.1. AU - Landecker, T. L. AU - Higgs, L. A. AU - Roger, R. S. AU - Seward, F. D. JO - Journal of the Royal Astronomical Society of Canada VL - 76 Y1 - 1982/10/1 SP - 322 KW - Supernova Remnants:X Rays UR - https://ui.adsabs.harvard.edu/abs/1982JRASC..76R.322L SN - 0035-872X ER - TY - CONF TI - High Resolution Soft X-Ray Spectra of Scorpius X-1: The Structure of Circumsource Accreting Material AU - Kahn, S. M. AU - Seward, F. D. AU - Chebowski, T. JO - Bulletin of the American Astronomical Society VL - 14 Y1 - 1982/09/1 SP - 944 UR - https://ui.adsabs.harvard.edu/abs/1982BAAS...14R.944K ER - TY - CONF TI - Further Einstein Results for the New Circinus Pulsar (PSR 1509-58) AU - Harnden, F. R., Jr. AU - Seward, F. D. JO - Bulletin of the American Astronomical Society VL - 14 Y1 - 1982/09/1 SP - 966 UR - https://ui.adsabs.harvard.edu/abs/1982BAAS...14Q.966H ER - TY - JOUR TI - X-ray spectrum of Capella and its relation to coronal structure and ultraviolet emission. AU - Mewe, R. AU - Gronenschild, E. H. B. M. AU - Westergaard, N. J. AU - Heise, J. AU - Seward, F. D. AU - Chlebowski, T. AU - Kuin, N. P. M. AU - Brinkman, A. C. AU - Dijkstra, J. H. AU - Schnopper, H. W. AD - 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) JO - The Astrophysical Journal VL - 260 Y1 - 1982/09/1 SP - 233 EP - 239 KW - Binary Stars KW - Stellar Coronas KW - X Ray Astronomy KW - X Ray Spectra KW - Abundance KW - Coronal Loops KW - Heao 2 KW - Ultraviolet Radiation KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1982ApJ...260..233M N2 - 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. PB - IOP DO - 10.1086/160249 SN - 0004-637X ER - TY - JOUR TI - Calibration and efficiency of the Einstein objective grating spectrometer AU - Seward, F. D. AU - Chlebowski, T. AU - Delvaille, J. P. AU - Henry, J. P. AU - Kahn, S. M. AU - van Speybroeck, L. AU - Dijkstra, J. H. AU - Brinkman, A. C. AU - Heise, J. AU - Mewe, R. AU - Schrijver, J. AD - 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) JO - Applied Optics VL - 21 Y1 - 1982/06/1 SP - 2012 EP - 2021 KW - Astronomical Spectroscopy KW - Calibrating KW - Gratings (Spectra) KW - Heao 2 KW - Image Resolution KW - Spaceborne Telescopes KW - X Ray Astronomy KW - Optical Paths KW - Prelaunch Problems KW - Run Time (Computers) KW - Spaceborne Astronomy KW - Spectral Resolution KW - Spacecraft Instrumentation KW - GRATINGS KW - X RAYS KW - SPACE OPTICS UR - https://ui.adsabs.harvard.edu/abs/1982ApOpt..21.2012S N2 - 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. DO - 10.1364/AO.21.002012 SN - 0003-6935 ER - TY - JOUR TI - X-ray emission from the Carina Nebula and the associated early stars. AU - Seward, F. D. AU - Chlebowski, T. AD - AA(Harvard Smithsonian Center for Astrophysics) JO - The Astrophysical Journal VL - 256 Y1 - 1982/05/1 SP - 530 EP - 542 KW - Diffuse Radiation KW - Early Stars KW - Hydrogen Clouds KW - Nebulae KW - O Stars KW - Wolf-Rayet Stars KW - X Ray Sources KW - Astronomical Maps KW - Astronomical Photography KW - Heao 2 KW - Interstellar Gas KW - Proportional Counters KW - Star Clusters KW - Stellar Luminosity KW - Stellar Winds KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1982ApJ...256..530S N2 - 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. PB - IOP DO - 10.1086/159929 SN - 0004-637X ER - TY - JOUR TI - A new, fast X-ray pulsar in the supernova remnant MSH 15-52. AU - Seward, F. D. AU - Harnden, F. R., Jr. AD - AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics) JO - The Astrophysical Journal VL - 256 Y1 - 1982/05/1 SP - L45 EP - L47 KW - Pulsars KW - Supernova Remnants KW - X Ray Sources KW - Nebulae KW - Periodic Variations KW - Astronomy UR - https://ui.adsabs.harvard.edu/abs/1982ApJ...256L..45S N2 - 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. PB - IOP DO - 10.1086/183793 SN - 0004-637X ER - TY - JOUR TI - Coordinated X-ray, optical and radio observations of flaring activityon YZ Canis Minoris. AU - Kahler, S. AU - Golub, L. AU - Harnden, F. R. AU - Liller, W. AU - Seward, F. AU - Vaiana, G. AU - Lovell, B. AU - Davis, R. J. AU - Spencer, R. E. AU - Whitehouse, D. R. AU - Feldman, P. A. AU - Viner, M. R. AU - Leslie, B. AU - Kahn, S. M. AU - Mason, K. O. AU - Davis, M. M. AU - Crannell, C. J. AU - Hobbs, R. W. AU - Schneeberger, T. J. AU - Worden, S. P. AU - Schommer, R. A. AU - Vogt, S. S. AU - Pettersen, B. R. AU - Coleman, G. D. AU - Karpen, J. T. AU - Giampapa, M. S. AU - Hege, E. K. AU - Pazzani, V. AU - Rodono, M. AU - Romeo, G. AU - Chugainov, P. F. AD - 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) JO - The Astrophysical Journal VL - 252 Y1 - 1982/01/1 SP - 239 EP - 249 KW - Dwarf Stars KW - Flare Stars KW - Late Stars KW - Radio Spectra KW - Stellar Flares KW - Stellar Spectrophotometry KW - X Ray Sources KW - Emission Spectra KW - Light (Visible Radiation) KW - M Stars KW - Periodic Variations KW - Radiant Flux Density KW - Stellar Spectra KW - Stellar Temperature KW - Ultraviolet Spectra KW - Astronomy UR - https://ui.adsabs.harvard.edu/abs/1982ApJ...252..239K N2 - 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. PB - IOP DO - 10.1086/159551 SN - 0004-637X ER - TY - JOUR TI - Einstein observations of supernova remnants AU - Seward, F. D. AD - AA(Harvard Smithsonian Center for Astrophysics) JO - Advances in Space Research VL - 2 Y1 - 1982/01/1 SP - 153 EP - 161 KW - Heao 2 KW - Stellar Spectra KW - Supernova Remnants KW - X Ray Astronomy KW - Interstellar Matter KW - Pulsars KW - Spatial Distribution KW - Spectral Resolution KW - Stellar Envelopes KW - Stellar Evolution KW - Stellar Mass Ejection KW - Stellar Temperature KW - X Ray Spectra KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1982AdSpR...2i.153S N2 - 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. DO - 10.1016/0273-1177(82)90266-6 SN - 0273-1177 ER - TY - JOUR TI - Results from an extensive Einstein stellar survey. AU - Vaiana, G. S. AU - Cassinelli, J. P. AU - Fabbiano, G. AU - Giacconi, R. AU - Golub, L. AU - Gorenstein, P. AU - Haisch, B. M. AU - Harnden, F. R., Jr. AU - Johnson, H. M. AU - Linsky, J. L. AU - Maxson, C. W. AU - Mewe, R. AU - Rosner, R. AU - Seward, F. AU - Topka, K. AU - Zwaan, C. AD - 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) JO - The Astrophysical Journal VL - 245 Y1 - 1981/04/1 SP - 163 EP - 182 KW - Early Stars KW - Hertzsprung-Russell Diagram KW - Main Sequence Stars KW - Stellar Coronas KW - X Ray Sources KW - B Stars KW - Emission Spectra KW - O Stars KW - Stellar Gravitation KW - Stellar Luminosity KW - Stellar Temperature KW - White Dwarf Stars KW - Astronomy UR - https://ui.adsabs.harvard.edu/abs/1981ApJ...245..163V N2 - 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. PB - IOP DO - 10.1086/158797 SN - 0004-637X ER - TY - CONF TI - New Einstein Observations of the Eta Carinae Nebula AU - Chlebowski, T. AU - Seward, F. D. JO - Bulletin of the American Astronomical Society VL - 13 Y1 - 1981/03/1 SP - 512 UR - https://ui.adsabs.harvard.edu/abs/1981BAAS...13..512C ER - TY - CONF TI - Search for Extended X-ray Emission Surrounding the Crab Nebula AU - Gorenstein, P. AU - Harnden, F. R., Jr. AU - Mitchell, M. AU - Seward, F. D. JO - Bulletin of the American Astronomical Society VL - 13 Y1 - 1981/03/1 SP - 865 UR - https://ui.adsabs.harvard.edu/abs/1981BAAS...13..865G ER - TY - CONF TI - The EINSTEIN Objective Grating X-ray Spectrum of the Crab Nebula AU - Kahn, S. M. AU - Seward, F. D. AU - Chlebowski, T. AU - Dijkstra, J. JO - Bulletin of the American Astronomical Society VL - 13 Y1 - 1981/03/1 SP - 865 UR - https://ui.adsabs.harvard.edu/abs/1981BAAS...13..865K ER - TY - CONF TI - MSH 15-5(2) - A SNR Containing 2 Compact X-ray Sources AU - Seward, F. AU - Murdin, P. JO - Bulletin of the American Astronomical Society VL - 13 Y1 - 1981/03/1 SP - 795 UR - https://ui.adsabs.harvard.edu/abs/1981BAAS...13R.795S ER - TY - JOUR TI - X-Ray Spectroscopic Investigation of the Coronal Structure of Capella AU - Gronenschild, E. H. B. M. AU - Mewe, R. AU - Westergaard, N. J. AU - Heise, J. AU - Seward, F. D. AU - Chlebowski, T. AU - Kuin, N. P. M. AU - Brinkman, A. C. AU - Dijkstra, J. H. AU - Schnopper, H. W. AD - 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) JO - Space Science Reviews VL - 30 Y1 - 1981/03/1 SP - 185 EP - 189 KW - Binary Stars KW - Stellar Spectrophotometry KW - Stellar Structure KW - X Ray Sources KW - X Ray Spectroscopy KW - Abundance KW - Emission Spectra KW - Gratings (Spectra) KW - Iron KW - Line Spectra KW - Neon KW - Spectral Resolution KW - Stellar Temperature KW - Temperature Distribution KW - Thermal Plasmas KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1981SSRv...30..185G N2 - 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. DO - 10.1007/BF01246017 SN - 0038-6308 ER - TY - CONF TI - The X-ray Lobes of SS433 AU - Watson, M. G. AU - Grindlay, J. E. AU - Seward, F. D. JO - Bulletin of the American Astronomical Society VL - 13 Y1 - 1981/03/1 SP - 834 UR - https://ui.adsabs.harvard.edu/abs/1981BAAS...13..834W ER - TY - CONF TI - X-ray Variability of SS433 AU - Grindlay, J. AU - Band, D. AU - Seward, F. AU - Leahy, D. AU - Weisskopf, M. JO - Bulletin of the American Astronomical Society VL - 13 Y1 - 1981/03/1 SP - 834 UR - https://ui.adsabs.harvard.edu/abs/1981BAAS...13..834G ER - TY - JOUR TI - An X-ray map of SN 1006 from the Einstein Observatory. AU - Pye, J. P. AU - Punds, K. A. AU - Rolf, D. P. AU - Seward, F. D. AU - Smith, A. AU - Willingale, R. AD - 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) JO - Monthly Notices of the Royal Astronomical Society VL - 194 Y1 - 1981/02/1 SP - 569 EP - 582 KW - Astronomical Maps KW - Supernova Remnants KW - X Ray Imagery KW - X Ray Sources KW - X Ray Spectra KW - Astronomical Observatories KW - Brightness KW - Emission Spectra KW - Image Resolution KW - Proportional Counters KW - Space Plasmas KW - Three Dimensional Models KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1981MNRAS.194..569P N2 - 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. PB - OUP DO - 10.1093/mnras/194.3.569 SN - 0035-8711 ER - TY - JOUR TI - X-ray survey of the Small Magellanic Cloud. AU - Seward, F. D. AU - Mitchell, M. AD - AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics) JO - The Astrophysical Journal VL - 243 Y1 - 1981/02/1 SP - 736 EP - 743 KW - Galactic Radiation KW - Magellanic Clouds KW - Stellar Radiation KW - X Ray Sources KW - Luminous Intensity KW - Proportional Counters KW - Stellar Coronas KW - Supernova Remnants KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1981ApJ...243..736S N2 - 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. PB - IOP DO - 10.1086/158641 SN - 0004-637X ER - TY - CHAP TI - The Einstein Observatory and future X-ray telescopes. AU - Giacconi, R. AU - Gorenstein, P. AU - Murray, S. S. AU - Schreier, E. AU - Seward, F. AU - Tananbaum, H. AU - Tucker, W. H. AU - van Speybroeck, L. AD - 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) JO - Telescopes for the 1980s, Annual Reviews Monograph Y1 - 1981/01/1 SP - 195 EP - 278 KW - Astronomical Observatories KW - Heao KW - Spaceborne Telescopes KW - X Ray Astronomy KW - X Ray Telescopes KW - Focal Plane Devices KW - Grazing Incidence KW - Grazing Incidence Telescopes KW - High Resolution KW - Mirrors KW - Proportional Counters KW - Ray Tracing KW - Solar X-Rays KW - Spaceborne Astronomy KW - Technological Forecasting KW - Astronomy KW - X-Ray Telescopes UR - https://ui.adsabs.harvard.edu/abs/1981tesc.book..195G N2 - 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. ER - TY - JOUR TI - Einstein X-ray observations of Proxima Centauri and the surrounding region AU - Haisch, B. M. AU - Harnden, F. R., Jr. AU - Seward, F. D. AU - Vaiana, G. S. AU - Linsky, J. L. AU - Rosner, R. AD - 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) JO - The Astrophysical Journal VL - 242 Y1 - 1980/12/1 SP - L99 EP - L103 KW - Flare Stars KW - Stellar Coronas KW - X Ray Astronomy KW - X Ray Stars KW - Stellar Envelopes KW - Stellar Luminosity KW - Stellar Models KW - Astronomy UR - https://ui.adsabs.harvard.edu/abs/1980ApJ...242L..99H N2 - 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. PB - IOP DO - 10.1086/183411 SN - 0004-637X ER - TY - JOUR TI - Diffuse X-ray emission from the jets of SS433 AU - Seward, F. AU - Grindlay, J. AU - Seaquist, E. AU - Gilmore, W. AD - AA(Harvard Smithsonian Center for Astrophysics), AB(Harvard Smithsonian Center for Astrophysics), AC(University of Toronto, Canada), AD(University of Toronto, Canada) JO - Nature VL - 287 Y1 - 1980/10/1 SP - 806 EP - 808 KW - Supernova Remnants KW - X Ray Sources KW - Diffuse Radiation KW - Heao KW - Periodic Variations KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1980Natur.287..806S N2 - 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. DO - 10.1038/287806a0 SN - 0028-0836 ER - TY - CONF TI - X-ray Images of the Crab Nebula AU - Harnden, F. R., Jr. AU - Giacconi, R. AU - Grindlay, J. AU - Hertz, P. AU - Schreier, E. AU - Seward, F. AU - Tananbaum, H. AU - van Speybroeck, L. JO - Bulletin of the American Astronomical Society VL - 12 Y1 - 1980/09/1 SP - 799 UR - https://ui.adsabs.harvard.edu/abs/1980BAAS...12..799H ER - TY - CONF TI - Observation of X-Rays from the Jovian System AU - Metzger, A. E. AU - Gilman, D. A. AU - Luthey, J. L. AU - Hurley, K. C. AU - Sullivan, J. D. AU - Seward, F. D. AU - Schnopper, H. W. JO - Bulletin of the American Astronomical Society VL - 12 Y1 - 1980/03/1 SP - 450 UR - https://ui.adsabs.harvard.edu/abs/1980BAAS...12..450M ER - TY - CONF TI - Coordinated X-Ray, Optical, and Radio Observations of Flares from the dMe Star YZ Canis Minoris AU - Kahler, S. W. AU - Golub, L. AU - Harnden, F. R. AU - Seward, F. D. AU - Vaiana, G. S. JO - Bulletin of the American Astronomical Society VL - 12 Y1 - 1980/03/1 SP - 526 UR - https://ui.adsabs.harvard.edu/abs/1980BAAS...12..526K ER - TY - JOUR TI - Preliminary Results of OGS X-Ray Observations of Capella AU - Mewe, R. AU - Gronenschild, E. H. B. M. AU - Brinkman, A. C. AU - Dijkstra, J. H. AU - Schrijver, J. AU - Heise, J. AU - Seward, F. D. AU - Schnopper, H. W. AU - Delvaille, J. P. JO - SAO Special Report VL - 389 Y1 - 1980/01/1 SP - 107 UR - https://ui.adsabs.harvard.edu/abs/1980SAOSR.389..107M SN - 0081-0320 ER - TY - CONF TI - Einstein observations of extended galactic X-ray sources AU - Seward, F. D. AD - AA(Smithsonian Astrophysical Observatory) JO - Marshall Space Flight Center HEAO Science Symposium Y1 - 1979/11/1 SP - 368 EP - 389 KW - Galaxies KW - Heao 2 KW - Spaceborne Telescopes KW - Supernova Remnants KW - X Ray Sources KW - Cassiopeia A KW - Crab Nebula KW - Neutron Stars KW - Spectrum Analysis KW - Space Radiation UR - https://ui.adsabs.harvard.edu/abs/1979msfc.symp..368S N2 - 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. ER - TY - JOUR TI - X-rays from Eta Carinae and the surrounding nebula. AU - Seward, F. D. AU - Forman, W. R. AU - Giacconi, R. AU - Griffiths, R. E. AU - Harnden, F. R., Jr. AU - Jones, C. AU - Pye, J. P. AD - 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) JO - The Astrophysical Journal VL - 234 Y1 - 1979/11/1 SP - L55 EP - L58 KW - Early Stars KW - Nebulae KW - Stellar Coronas KW - X Ray Sources KW - Astrophysics KW - Stellar Luminosity KW - Wolf-Rayet Stars KW - Astrophysics KW - Carina Nebula:X Rays KW - Wolf-Rayet Stars:X Rays KW - X-Ray Sources:Optical Identifications UR - https://ui.adsabs.harvard.edu/abs/1979ApJ...234L..55S N2 - 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. PB - IOP DO - 10.1086/183108 SN - 0004-637X ER - TY - JOUR TI - A high-sensitivity X-ray survey using the Einstein Observatory and the discrete source contribution to the extragalactic X-ray background. AU - Giacconi, R. AU - Bechtold, J. AU - Branduardi, G. AU - Forman, W. AU - Henry, J. P. AU - Jones, C. AU - Kellogg, E. AU - van der Laan, H. AU - Liller, W. AU - Marshall, H. AU - Murray, S. S. AU - Pye, J. AU - Schreier, E. AU - Sargent, W. L. W. AU - Seward, F. AU - Tananbaum, H. AD - 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) JO - The Astrophysical Journal VL - 234 Y1 - 1979/11/1 SP - L1 EP - L7 KW - Background Radiation KW - Cosmic Rays KW - Heao 2 KW - X Ray Sources KW - Astronomical Observatories KW - Extraterrestrial Radiation KW - Sensitivity KW - Astrophysics KW - Positions:X-Ray Sources KW - X-Ray Background KW - X-Ray Sources:Optical Identifications KW - X-Ray Sources:Surveys UR - https://ui.adsabs.harvard.edu/abs/1979ApJ...234L...1G N2 - 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. PB - IOP DO - 10.1086/183099 SN - 0004-637X ER - TY - CONF TI - X-Ray Observations of the Crab Nebula with the Einstein Observatory. AU - Harnden, F. R., Jr. AU - Buehler, B. AU - Giacconi, R. AU - Grindlay, J. AU - Hertz, P. AU - Schreier, E. AU - Seward, F. AU - Tananbaum, H. AU - van Speybroeck, L. JO - Bulletin of the American Astronomical Society VL - 11 Y1 - 1979/09/1 SP - 789 UR - https://ui.adsabs.harvard.edu/abs/1979BAAS...11..789H ER - TY - CONF TI - On Stars and OB Associations Observed from EINSTEIN. AU - Harnden, F. R., Jr. AU - Golub, L. AU - Rosner, R. AU - Seward, F. AU - Topka, K. AU - Vaiana, G. S. JO - Bulletin of the American Astronomical Society VL - 11 Y1 - 1979/09/1 SP - 775 UR - https://ui.adsabs.harvard.edu/abs/1979BAAS...11..775H ER - TY - CONF TI - An X-ray Map of the W44 Supernova Remnant from the EINSTEIN Observatory. AU - Rolf, D. AU - Harnden, F. R. AU - Gorenstein, P. AU - Pye, J. P. AU - Seward, F. D. AU - Willingale, R. JO - Bulletin of the American Astronomical Society VL - 11 Y1 - 1979/09/1 SP - 796 UR - https://ui.adsabs.harvard.edu/abs/1979BAAS...11..796R ER - TY - CONF TI - An X-ray Map of SN 1006 with the EINSTEIN Observatory. AU - Pye, J. P. AU - Pounds, K. A. AU - Rolf, D. AU - Seward, F. D. AU - Smith, A. AU - Willingale, R. JO - Bulletin of the American Astronomical Society VL - 11 Y1 - 1979/09/1 SP - 790 UR - https://ui.adsabs.harvard.edu/abs/1979BAAS...11..790P ER - TY - CONF TI - Observations of X-ray sources in M31 with the Einstein Observatory. AU - van Speybroeck, L. AU - Bechtold, J. AU - Epstein, A. AU - Forman, W. AU - Giacconi, R. AU - Grindlay, J. AU - Jones, C. AU - Murray, S. AU - Schreier, E. AU - Seward, F. JO - Bulletin of the American Astronomical Society VL - 11 Y1 - 1979/06/1 SP - 609 KW - Andromeda Nebula:X-Ray Sources UR - https://ui.adsabs.harvard.edu/abs/1979BAAS...11..609V ER - TY - JOUR TI - The Einstein (HEAO 2) X-ray Observatory. AU - Giacconi, R. AU - Branduardi, G. AU - Briel, U. AU - Epstein, A. AU - Fabricant, D. AU - Feigelson, E. AU - Forman, W. AU - Gorenstein, P. AU - Grindlay, J. AU - Gursky, H. AU - Harnden, F. R. AU - Henry, J. P. AU - Jones, C. AU - Kellogg, E. AU - Koch, D. AU - Murray, S. AU - Schreier, E. AU - Seward, F. AU - Tananbaum, H. AU - Topka, K. AU - Van Speybroeck, L. AU - Holt, S. S. AU - Becker, R. H. AU - Boldt, E. A. AU - Serlemitsos, P. J. AU - Clark, G. AU - Canizares, C. AU - Markert, T. AU - Novick, R. AU - Helfand, D. AU - Long, K. AD - 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) JO - The Astrophysical Journal VL - 230 Y1 - 1979/06/1 SP - 540 EP - 550 KW - Heao 2 KW - Spaceborne Astronomy KW - X Ray Astronomy KW - Cameras KW - Focal Plane Devices KW - High Resolution KW - Proportional Counters KW - Spaceborne Telescopes KW - Spacecraft Instruments KW - Spectrometers KW - Astronomy KW - X-Ray Telescopes UR - https://ui.adsabs.harvard.edu/abs/1979ApJ...230..540G N2 - 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. PB - IOP DO - 10.1086/157110 SN - 0004-637X ER - TY - CONF TI - Observations of the Vela Pulsar from the Einstein Observatory AU - Harnden, F. R., Jr. AU - Hertz, P. AU - Gorenstein, P. AU - Grindlay, J. AU - Schreier, E. AU - Seward, F. JO - Bulletin of the American Astronomical Society VL - 11 Y1 - 1979/03/1 SP - 424 UR - https://ui.adsabs.harvard.edu/abs/1979BAAS...11..424H ER - TY - CONF TI - Initial Results from the Einstein Survey of Stellar Low-Luminosity X-ray Sources AU - Vaiana, G. AU - Forman, W. AU - Giacconi, R. AU - Gorenstein, P. AU - Pye, J. AU - Rosner, R. AU - Seward, F. AU - Topka, K. JO - Bulletin of the American Astronomical Society VL - 11 Y1 - 1979/03/1 SP - 446 UR - https://ui.adsabs.harvard.edu/abs/1979BAAS...11..446V ER - TY - CONF TI - X-Ray Sources from O Star Associations AU - Rosner, R. AU - Grindlay, G. AU - Harnden, R. AU - Seward, F. AU - Vaiana, G. JO - Bulletin of the American Astronomical Society VL - 11 Y1 - 1979/03/1 SP - 446 UR - https://ui.adsabs.harvard.edu/abs/1979BAAS...11..446R ER - TY - CONF TI - A High Resolution X-Ray Image of the Remnant of Tycho's Supernova from the Einstein Observatory AU - Gorenstein, P. AU - Murray, S. AU - Epstein, A. AU - Griffiths, R. AU - Fabbiano, G. AU - Seward, F. JO - Bulletin of the American Astronomical Society VL - 11 Y1 - 1979/03/1 SP - 462 UR - https://ui.adsabs.harvard.edu/abs/1979BAAS...11..462G ER - TY - CONF TI - X-ray Surveys Using Einstein: A Medium Sensitivity Survey and Spectra of "Deep Survey" Sources AU - Marshall, H. AU - Seward, F. AU - Schwartz, D. AU - Giacconi, R. JO - Bulletin of the American Astronomical Society VL - 11 Y1 - 1979/03/1 SP - 442 UR - https://ui.adsabs.harvard.edu/abs/1979BAAS...11..442M ER - TY - CONF TI - X-Ray Observations of the Crab Nebula with the Einstein Observatory AU - Tananbaum, H. AU - Epstein, A. AU - Forman, W. AU - Giacconi, R. AU - Grindlay, J. AU - Harden, F. R., Jr. AU - Jones, C. AU - Schreier, E. AU - Seward, F. AU - van Speybroeck, L. JO - Bulletin of the American Astronomical Society VL - 11 Y1 - 1979/03/1 SP - 424 UR - https://ui.adsabs.harvard.edu/abs/1979BAAS...11..424T ER - TY - JOUR TI - HEAO 2 AU - Giacconi, R. AU - Seward, F. JO - International Astronomical Union Circular VL - 3309 Y1 - 1978/11/1 SP - 2 UR - https://ui.adsabs.harvard.edu/abs/1978IAUC.3309....2G N2 - 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. SN - 0081-0304 ER - TY - JOUR TI - HEAO B AU - Seward, F. D. JO - International Astronomical Union Circular VL - 3245 Y1 - 1978/07/1 SP - 1 UR - https://ui.adsabs.harvard.edu/abs/1978IAUC.3245....1S N2 - 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)." SN - 0081-0304 ER - TY - JOUR TI - A trip to the Crab Nebula. AU - Seward, F. D. AD - AA(Smithsonian Astrophysical Observatory) JO - Journal of the British Interplanetary Society VL - 31 Y1 - 1978/03/1 SP - 83 EP - 92 KW - Crab Nebula KW - Pulsars KW - Radiation Sources KW - Supernovae KW - Background Radiation KW - Radiation Hazards KW - Supernova Remnants KW - Space Sciences (General) KW - Crab Nebula UR - https://ui.adsabs.harvard.edu/abs/1978JBIS...31...83S N2 - 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. SN - 0007-084X ER - TY - JOUR TI - The Ariel V (SSI) catalogue of high galactic latitude ( AU - Cooke, B. A. AU - Ricketts, M. J. AU - Maccacaro, T. AU - Pye, J. P. AU - Elvis, M. AU - Watson, M. G. AU - Griffiths, R. E. AU - Pounds, K. A. AU - McHardy, I. AU - Maccagni, D. AU - Seward, F. D. AU - Page, C. G. AU - Turner, M. J. L. AD - 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) JO - Monthly Notices of the Royal Astronomical Society VL - 182 Y1 - 1978/02/1 SP - 489 EP - 515 KW - Ariel 5 Satellite KW - Astronomical Catalogs KW - Cosmic X Rays KW - Milky Way Galaxy KW - X Ray Astronomy KW - Data Processing KW - Galactic Clusters KW - Luminous Intensity KW - Sky Surveys (Astronomy) KW - Spaceborne Astronomy KW - X Ray Sources KW - Astronomy KW - Catalogues:X-Ray Sources KW - X-Ray Sources: Optical Identifications UR - https://ui.adsabs.harvard.edu/abs/1978MNRAS.182..489C N2 - 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. PB - OUP DO - 10.1093/mnras/182.3.489 SN - 0035-8711 ER - TY - JOUR TI - The X-Ray Spectrum and Structure of the Puppis a Supernova Remnant AU - Zarnecki, J. C. AU - Culhane, J. L. AU - Toor, A. AU - Seward, F. D. AU - Charles, P. A. JO - The Astrophysical Journal VL - 219 Y1 - 1978/01/1 SP - L17 UR - https://ui.adsabs.harvard.edu/abs/1978ApJ...219L..17Z PB - IOP DO - 10.1086/182598 SN - 0004-637X ER - TY - JOUR TI - Was the bright transient X-ray source Centaurus XR-4 I a globular cluster? AU - Seward, F. D. AU - Liller, W. JO - Publications of the Astronomical Society of the Pacific VL - 89 Y1 - 1977/10/1 SP - 696 EP - 698 KW - Globular Clusters:X-Ray Sources KW - X-Ray Sources: Transient UR - https://ui.adsabs.harvard.edu/abs/1977PASP...89..696S N2 - 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 PB - IOP DO - 10.1086/130211 SN - 0004-6280 ER - TY - JOUR TI - Observation of X-rays from the Crab pulsar. AU - Toor, A. AU - Seward, F. D. AD - AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California) JO - The Astrophysical Journal VL - 216 Y1 - 1977/09/1 SP - 560 EP - 564 KW - Crab Nebula KW - Neutron Stars KW - Pulsars KW - X Ray Sources KW - Black Body Radiation KW - Lunar Occultation KW - Photons KW - Spectral Energy Distribution KW - X Ray Astronomy KW - Astronomy UR - https://ui.adsabs.harvard.edu/abs/1977ApJ...216..560T N2 - 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. PB - IOP DO - 10.1086/155497 SN - 0004-637X ER - TY - JOUR TI - Observations of the LMC X-ray sources with the Ariel V Sky Survey Instrument. AU - Griffiths, R. E. AU - Seward, F. D. AD - AA(University of Leicester, UK) JO - Monthly Notices of the Royal Astronomical Society VL - 180 Y1 - 1977/08/1 SP - 75P EP - 79 KW - Galactic Radiation KW - Luminous Intensity KW - Magellanic Clouds KW - Sky Surveys (Astronomy) KW - X Ray Sources KW - Astronomical Maps KW - Satellite Observation KW - Spaceborne Astronomy KW - X Ray Astronomy KW - Astronomy UR - https://ui.adsabs.harvard.edu/abs/1977MNRAS.180P..75G N2 - 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. PB - OUP DO - 10.1093/mnras/180.1.75P SN - 0035-8711 ER - TY - JOUR TI - Argon fluorescent X rays in the Earth's atmosphere during solar flares AU - Seward, F. D. AU - Horton, B. AU - Pollard, G. AU - Sanford, P. W. AD - AA(University College London, UK), AB(University College London, UK), AC(University College London, UK) JO - Nature VL - 264 Y1 - 1976/12/1 SP - 421 EP - 423 KW - Argon KW - Earth Albedo KW - Earth Atmosphere KW - Radiant Flux Density KW - Solar Flares KW - X Ray Fluorescence KW - Ariel 5 Satellite KW - Atmospheric Composition KW - Energy Spectra KW - Proportional Counters KW - Solar X-Rays KW - X Ray Scattering KW - Geophysics UR - https://ui.adsabs.harvard.edu/abs/1976Natur.264..421S N2 - 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. DO - 10.1038/264421a0 SN - 0028-0836 ER - TY - JOUR TI - X-ray sources in the southern Milky Way. AU - Seward, F. D. AU - Page, C. G. AU - Turner, M. J. L. AU - Pounds, K. A. AD - AA(University of Leicester, UK), AB(University of Leicester, UK), AC(University of Leicester, UK), AD(University of Leicester, UK) JO - Monthly Notices of the Royal Astronomical Society VL - 177 Y1 - 1976/10/1 SP - 13P EP - 20 KW - Milky Way Galaxy KW - Supernova Remnants KW - Variable Stars KW - X Ray Sources KW - Astronomical Catalogs KW - Astronomical Maps KW - Error Analysis KW - Satellite-Borne Instruments KW - Sky Surveys (Astronomy) KW - Tables (Data) KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1976MNRAS.177P..13S N2 - 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. PB - OUP DO - 10.1093/mnras/177.1.13P SN - 0035-8711 ER - TY - JOUR TI - Implosion experiments with an asymmetrically irradiated laser fusion target AU - Holzrichter, J. F. AU - Ahlstrom, H. G. AU - Speck, D. R. AU - Storm, E. AU - Swain, J. E. AU - Coleman, L. W. AU - Hendricks, C. D. AU - Kornblum, H. N. AU - Seward, F. D. AU - Slivinsky, V. W. AD - 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) JO - Plasma Physics VL - 18 Y1 - 1976/09/1 SP - 675 EP - 680 KW - Deuterium Plasma KW - Fusion Reactors KW - Laser Fusion KW - Plasma Heating KW - Compressible Fluids KW - Implosions KW - Neodymium Lasers KW - Reactor Technology KW - Tritium KW - Plasma Physics UR - https://ui.adsabs.harvard.edu/abs/1976PlPh...18..675H N2 - 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. DO - 10.1088/0032-1028/18/9/002 SN - 0032-1028 ER - TY - CONF TI - The X-ray Temperature of Puppis A. AU - Charles, P. A. AU - Culhane, J. L. AU - Zarnecki, J. C. AU - Seward, F. D. AU - Toor, A. JO - Bulletin of the American Astronomical Society VL - 8 Y1 - 1976/09/1 SP - 529 UR - https://ui.adsabs.harvard.edu/abs/1976BAAS....8..529C ER - TY - JOUR TI - Evidence for "thermal" X-rays from the Crab nebula. AU - Toor, A. AU - Palmieri, T. M. AU - Seward, F. D. AD - AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California), AC(Lawrence Livermore National Laboratory, California) JO - The Astrophysical Journal VL - 207 Y1 - 1976/07/1 SP - 96 EP - 101 KW - Crab Nebula KW - Lunar Occultation KW - Pulsars KW - Rocket-Borne Instruments KW - Supernova Remnants KW - X Ray Sources KW - Astronomical Models KW - Interstellar Matter KW - Point Sources KW - Radio Sources (Astronomy) KW - Spectrum Analysis KW - X Ray Scattering KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1976ApJ...207...96T N2 - 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. PB - IOP DO - 10.1086/154471 SN - 0004-637X ER - TY - CONF TI - X-ray Sources in the Aquilla-Serpens-Scutum Region AU - Seward, F. D. AU - Page, C. G. AU - Turner, M. J. AU - Pounds, K. A. JO - Bulletin of the American Astronomical Society VL - 8 Y1 - 1976/06/1 SP - 443 UR - https://ui.adsabs.harvard.edu/abs/1976BAAS....8..443S ER - TY - JOUR TI - X-ray sources in the Aquila-Serpens-Scutum region. AU - Seward, F. D. AU - Page, C. G. AU - Turner, M. J. L. AU - Pounds, K. A. AD - AA(University of Leicester, UK), AB(University of Leicester, UK), AC(University of Leicester, UK), AD(University of Leicester, UK) JO - Monthly Notices of the Royal Astronomical Society VL - 175 Y1 - 1976/05/1 SP - 39P EP - 46 KW - Galactic Radiation KW - Satellite Observation KW - X Ray Sources KW - Ariel Satellites KW - Data Reduction KW - Graphs (Charts) KW - Sky Surveys (Astronomy) KW - Supernova Remnants KW - Uhuru Satellite KW - Astronomy UR - https://ui.adsabs.harvard.edu/abs/1976MNRAS.175P..39S N2 - 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. PB - OUP DO - 10.1093/mnras/175.1.39P SN - 0035-8711 ER - TY - JOUR TI - Calibrated ''four-color'' x-ray microscope for laser plasma diagnostics AU - Seward, F. AU - Dent, J. AU - Boyle, M. AU - Koppel, L. AU - Harper, T. AU - Stoering, P. AU - Toor, A. AD - 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) JO - Review of Scientific Instruments VL - 47 Y1 - 1976/04/1 SP - 464 EP - 470 KW - Laser Fusion KW - Laser Plasmas KW - Microscopy KW - Plasma Diagnostics KW - X Ray Apparatus KW - Calibrating KW - Electromagnetic Wave Filters KW - Energy Spectra KW - Mirrors KW - Radiography KW - X Ray Spectra KW - Instrumentation and Photography KW - 52.70.Kz KW - Optical measurements UR - https://ui.adsabs.harvard.edu/abs/1976RScI...47..464S N2 - 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. PB - AIP DO - 10.1063/1.1134656 SN - 0034-6748 ER - TY - JOUR TI - An empirical comparison of X-ray and radio emission from supernova remnants. AU - Seward, F. AU - Burginyon, G. AU - Grader, R. AU - Hill, R. AU - Palmieri, T. AU - Stoering, P. AU - Toor, A. AD - 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) JO - The Astrophysical Journal VL - 205 Y1 - 1976/04/1 SP - 238 EP - 246 KW - Astronomical Catalogs KW - Radio Emission KW - Supernova Remnants KW - X Ray Sources KW - Luminosity KW - Radio Sources (Astronomy) KW - Rocket Sounding KW - Statistical Correlation KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1976ApJ...205..238S N2 - 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. PB - IOP DO - 10.1086/154269 SN - 0004-637X ER - TY - CONF TI - X-ray and gamma-ray astronomy. AU - Fichtel, C. E. AU - Mumford, G. S. AU - Lindquist, T. R. AU - Webber, W. R. AU - Seward, F. D. AU - Page, T. AU - Jones, C. AU - Forman, W. AU - Liller, W. JO - Space Science and Astronomy. Escape from Earth Y1 - 1976/01/1 SP - 355 EP - 386 UR - https://ui.adsabs.harvard.edu/abs/1976ssae.conf..355F ER - TY - JOUR TI - Spatial distribution of X-rays in the Crab nebula. AU - Palmieri, T. M. AU - Seward, F. D. AU - Toor, A. AU - van Flandern, T. C. AD - 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.) JO - The Astrophysical Journal VL - 202 Y1 - 1975/12/1 SP - 494 EP - 497 KW - Crab Nebula KW - Lunar Occultation KW - Radiation Distribution KW - Supernovae KW - X Ray Astronomy KW - Pulsars KW - Radiant Flux Density KW - Radiation Sources KW - Spatial Distribution KW - Stellar Luminosity KW - Astronomy UR - https://ui.adsabs.harvard.edu/abs/1975ApJ...202..494P N2 - 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 PB - IOP DO - 10.1086/153998 SN - 0004-637X ER - TY - CONF TI - X-ray microscopy of laser fusion targets in four energy bands from 0.7 to 4.0 keV AU - Boyle, M. J. AU - Seward, F. D. AU - Harper, T. L. AU - Koppel, L. N. AU - Pettipiece, K. J. AU - Ahlstrom, H. G. AD - 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) JO - Presented at APS Meeting Y1 - 1975/10/1 SP - 10 EP - 14 KW - Laser Fusion KW - Laser Plasmas KW - X Ray Analysis KW - Calibrating KW - Microscopy KW - Photographs KW - Radiation Measurement KW - Spatial Distribution KW - Spectral Energy Distribution KW - X Ray Spectra KW - Lasers and Masers UR - https://ui.adsabs.harvard.edu/abs/1975aps..meet...10B N2 - 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. ER - TY - JOUR TI - A soft X-ray survey of the Scutum-Serpens-Aquila region. AU - Hill, R. W. AU - Burginyon, G. A. AU - Seward, F. D. JO - The Astrophysical Journal VL - 200 Y1 - 1975/09/1 SP - 709 EP - 714 UR - https://ui.adsabs.harvard.edu/abs/1975ApJ...200..709H N2 - 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 PB - IOP DO - 10.1086/153841 SN - 0004-637X ER - TY - JOUR TI - Analysis of X-ray spectra reveals possibility of enhanced silicon in three supernova remnants. AU - Burginyon, G. A. AU - Hill, R. W. AU - Seward, F. D. AD - AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California), AC(Lawrence Livermore National Laboratory, California) JO - The Astrophysical Journal VL - 200 Y1 - 1975/08/1 SP - 163 EP - 170 KW - Abundance KW - Plasma Radiation KW - Silicon KW - Supernova Remnants KW - X Ray Spectra KW - High Temperature Plasmas KW - Interstellar Matter KW - Spectrum Analysis KW - X Ray Astronomy KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1975ApJ...200..163B N2 - 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 PB - IOP DO - 10.1086/153773 SN - 0004-637X ER - TY - JOUR TI - The Soft X-Ray Spectra of Cassiopeia a and Tycho's Supernova Remnant AU - Hill, R. W. AU - Burginyon, G. A. AU - Seward, F. D. JO - The Astrophysical Journal VL - 200 Y1 - 1975/08/1 SP - 158 EP - 162 UR - https://ui.adsabs.harvard.edu/abs/1975ApJ...200..158H N2 - 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 PB - IOP DO - 10.1086/153772 SN - 0004-637X ER - TY - CONF TI - A Possible Extended Soft X-Ray Component of the Crab Nebula AU - Toor, A. AU - Palmieri, T. M. AU - Seward, F. D. JO - Bulletin of the American Astronomical Society VL - 7 Y1 - 1975/06/1 SP - 456 UR - https://ui.adsabs.harvard.edu/abs/1975BAAS....7..456T ER - TY - CONF TI - The Soft X-ray Spectra of Cas A and Tycho's Supernova Remnant. AU - Hill, R. W. AU - Burginyon, G. A. AU - Seward, F. D. JO - Bulletin of the American Astronomical Society VL - 7 Y1 - 1975/03/1 SP - 246 UR - https://ui.adsabs.harvard.edu/abs/1975BAAS....7..246H ER - TY - CONF TI - Crab Nebula X-ray Lunar Occultation. AU - Toor, A. AU - Palmieri, T. AU - Seward, F. JO - Bulletin of the American Astronomical Society VL - 7 Y1 - 1975/03/1 SP - 247 UR - https://ui.adsabs.harvard.edu/abs/1975BAAS....7..247T ER - TY - JOUR TI - A simple x-ray microscope for photographing laser produced plasmas AU - Seward, F. D. AU - Palmieri, T. M. AD - AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California) JO - Review of Scientific Instruments VL - 46 Y1 - 1975/02/1 SP - 204 EP - 206 KW - High Resolution KW - Laser Plasmas KW - Microscopes KW - Radiography KW - X Ray Apparatus KW - Calibrating KW - Lens Design KW - Photosensitivity KW - Plasma Radiation KW - Spherical Shells KW - Instrumentation and Photography KW - 52.70.-m KW - 52.50.Jm KW - 07.85.+n KW - Plasma diagnostic techniques and instrumentation KW - Plasma production and heating by laser beams UR - https://ui.adsabs.harvard.edu/abs/1975RScI...46..204S N2 - 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. PB - AIP DO - 10.1063/1.1134167 SN - 0034-6748 ER - TY - CONF TI - Adaptation of recent thermal model calculations to X-ray spectra of three old supernova remnants AU - Burginyon, G. A. AU - Hill, R. W. AU - Seward, F. D. AD - AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California), AC(Lawrence Livermore National Laboratory, California) JO - X-Rays in Space - Cosmic, Solar, and Auroral X-Rays, Volume 1 VL - 2 Y1 - 1975/01/1 SP - 975 EP - 984 KW - Abundance KW - Astronomical Models KW - Energy Spectra KW - Supernova Remnants KW - Thermal Radiation KW - X Ray Spectra KW - Atomic Spectra KW - Chemical Composition KW - Emission Spectra KW - Line Spectra KW - Optical Properties KW - Solar Corona KW - Astrophysics UR - https://ui.adsabs.harvard.edu/abs/1975xris.conf..975B ER - TY - CONF TI - Joint cosmic/auroral X-ray panel discussion AU - Seward, F. D. AD - AA(Lawrence Livermore National Laboratory, California) JO - X-Rays in Space - Cosmic, Solar, and Auroral X-Rays, Volume 1 VL - 2 Y1 - 1975/01/1 SP - 1121 EP - 1126 KW - Auroral Zones KW - Electron Precipitation KW - X Ray Astronomy KW - Background Radiation KW - Electron Counters KW - Electron Flux Density KW - Geomagnetism KW - Radiant Flux Density KW - Radiation Detectors KW - Rocket Sounding KW - Satellite Observation KW - Space Radiation UR - https://ui.adsabs.harvard.edu/abs/1975xris.conf.1121S N2 - 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. ER - TY - CONF TI - A review of soft X-ray astronomy AU - Seward, F. D. AD - AA(Lawrence Livermore National Laboratory, California) JO - X-Rays in Space - Cosmic, Solar, and Auroral X-Rays, Volume 1 VL - 1 Y1 - 1975/01/1 SP - 378 EP - 399 KW - Interstellar Extinction KW - Pulsars KW - Spaceborne Astronomy KW - X Ray Absorption KW - X Ray Astronomy KW - Background Radiation KW - Diffuse Radiation KW - Energy Spectra KW - Interstellar Matter KW - Milky Way Galaxy KW - Satellite Observation KW - Uhuru Satellite KW - Astronomy UR - https://ui.adsabs.harvard.edu/abs/1975xris.conf..378S N2 - 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. ER - TY - CONF TI - Summary - Cosmic X-rays AU - Seward, F. D. AD - AA(Lawrence Livermore National Laboratory, California) JO - X-Rays in Space - Cosmic, Solar, and Auroral X-Rays, Volume 1 VL - 2 Y1 - 1975/01/1 SP - 1175 EP - 1186 KW - Background Noise KW - Cosmic Rays KW - X Ray Astronomy KW - X Ray Sources KW - Binary Stars KW - Galactic Radiation KW - Gamma Rays KW - Solar X-Rays KW - Supernova Remnants KW - Surveys KW - Terrestrial Radiation KW - Space Radiation UR - https://ui.adsabs.harvard.edu/abs/1975xris.conf.1175S N2 - 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. ER - TY - JOUR TI - The Crab nebula as a calibration source for X-ray astronomy. AU - Toor, A. AU - Seward, F. D. AD - AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California) JO - The Astronomical Journal VL - 79 Y1 - 1974/10/1 SP - 995 EP - 999 KW - Calibrating KW - Crab Nebula KW - X Ray Astronomy KW - X Ray Spectra KW - Energy Spectra KW - Pulsars KW - Spectrum Analysis KW - X Ray Sources KW - Astronomy UR - https://ui.adsabs.harvard.edu/abs/1974AJ.....79..995T N2 - 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. PB - IOP DO - 10.1086/111643 SN - 0004-6256 ER - TY - JOUR TI - An Unusual X-Ray Source in Scutum AU - Hill, R. AU - Burginyon, G. AU - Grader, R. AU - Toor, A. AU - Stoering, J. AU - Seward, F. JO - The Astrophysical Journal VL - 189 Y1 - 1974/04/1 SP - L69 UR - https://ui.adsabs.harvard.edu/abs/1974ApJ...189L..69H N2 - 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 PB - IOP DO - 10.1086/181466 SN - 0004-637X ER - TY - CONF TI - X-ray Survey of Scutum - Aquila Region AU - Hill, D. W. AU - Burginyon, G. AU - Grader, R. AU - Stoering, J. P. AU - Seward, F. D. AU - Toor, A. JO - Bulletin of the American Astronomical Society VL - 6 Y1 - 1974/03/1 SP - 272 UR - https://ui.adsabs.harvard.edu/abs/1974BAAS....6Q.272H ER - TY - JOUR TI - A Search for Soft X-Ray Sources in the Galactic Anticenter. Absorption of X-Rays from the Crab Nebula AU - Hill, R. W. AU - Burginyon, G. A. AU - Seward, F. D. AU - Stoering, J. P. AU - Toor, A. JO - The Astrophysical Journal VL - 187 Y1 - 1974/02/1 SP - 505 EP - 510 UR - https://ui.adsabs.harvard.edu/abs/1974ApJ...187..505H N2 - 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 PB - IOP DO - 10.1086/152660 SN - 0004-637X ER - TY - CONF TI - The geographical distribution of ≡ 100-keV electrons above the earth's atmosphere. AU - Seward, F. D. JO - Electron Contamination in X-ray Astronomy Experiments Y1 - 1974/01/1 SP - 3 UR - https://ui.adsabs.harvard.edu/abs/1974ecxa.confE...3S ER - TY - CONF TI - Electrons at low altitudes: a difficult background problem for soft X-ray astronomy. AU - Seward, F. D. AU - Grader, R. J. AU - Toor, A. AU - Burginyon, G. A. AU - Hill, R. W. JO - Electron Contamination in X-ray Astronomy Experiments Y1 - 1974/01/1 SP - 1 UR - https://ui.adsabs.harvard.edu/abs/1974ecxa.confE...1S ER - TY - JOUR TI - Observations of soft X-rays: Upper limits on the flux from SN 1972E and measurements of the diffuse background in Centaurus. AU - Palmieri, T. M. AU - Burginyon, G. A. AU - Hill, R. W. AU - Scudder, J. K. AU - Seward, F. D. AU - Toor, A. JO - The Astrophysical Journal VL - 182 Y1 - 1973/06/1 SP - 411 UR - https://ui.adsabs.harvard.edu/abs/1973ApJ...182..411P N2 - 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 PB - IOP DO - 10.1086/152149 SN - 0004-637X ER - TY - JOUR TI - The Distribution of X-Ray Sources in Our Galaxy AU - Seward, Frederick D. JO - Sky and Telescope VL - 45 Y1 - 1973/04/1 SP - 220 UR - https://ui.adsabs.harvard.edu/abs/1973S&T....45..220S SN - 0037-6604 ER - TY - JOUR TI - Observation of Structure in the X-Ray Spectrum of Puppis a AU - Burginyon, G. AU - Hill, R. AU - Seward, F. AU - Tarter, B. AU - Toor, A. JO - The Astrophysical Journal VL - 180 Y1 - 1973/03/1 SP - L75 UR - https://ui.adsabs.harvard.edu/abs/1973ApJ...180L..75B N2 - 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 PB - IOP DO - 10.1086/181156 SN - 0004-637X ER - TY - JOUR TI - A Soft X-Ray Survey from the Galactic Center to Cassiopeia AU - Burginyon, G. AU - Hill, R. AU - Palmieri, T. AU - Scudder, J. AU - Seward, F. AU - Stoering, J. AU - Toor, A. JO - The Astrophysical Journal VL - 179 Y1 - 1973/01/1 SP - 615 EP - 626 UR - https://ui.adsabs.harvard.edu/abs/1973ApJ...179..615B N2 - 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 PB - IOP DO - 10.1086/151900 SN - 0004-637X ER - TY - JOUR TI - Applications of Low Energy and Gamma Rays AU - Seward, Frederick D. JO - Nuclear Technology VL - 16 Y1 - 1972/12/1 SP - 571 EP - 571 UR - https://ui.adsabs.harvard.edu/abs/1972NucTe..16..571S DO - 10.13182/NT72-A31229 ER - TY - JOUR TI - Observations of Soft X-Rays Two Supernova Remnants in the Constellation Lupus and the Diffuse Background AU - Palmieri, T. M. AU - Burginyon, G. A. AU - Hill, R. W. AU - Scudder, J. K. AU - Seward, F. D. JO - The Astrophysical Journal VL - 177 Y1 - 1972/11/1 SP - 387 UR - https://ui.adsabs.harvard.edu/abs/1972ApJ...177..387P N2 - 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. PB - IOP DO - 10.1086/151716 SN - 0004-637X ER - TY - JOUR TI - Distances and Absolute Luminosities of Galactic X-Ray Sources AU - Seward, F. D. AU - Burginyon, G. A. AU - Grader, R. J. AU - Hill, R. W. AU - Palmieri, T. M. JO - The Astrophysical Journal VL - 178 Y1 - 1972/11/1 SP - 131 EP - 142 UR - https://ui.adsabs.harvard.edu/abs/1972ApJ...178..131S N2 - 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. PB - IOP DO - 10.1086/151773 SN - 0004-637X ER - TY - JOUR TI - Observation of Several X-Ray Sources in 1970 September AU - Price, R. E. AU - Seward, F. D. AU - Swift, C. D. JO - The Astrophysical Journal VL - 176 Y1 - 1972/09/1 SP - 611 UR - https://ui.adsabs.harvard.edu/abs/1972ApJ...176..611P N2 - 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. PB - IOP DO - 10.1086/151662 SN - 0004-637X ER - TY - JOUR TI - The Role of Modern Sensor Applications in the United Nations Resource Exploration and Evaluation Programs AU - Seward, Franklin JO - IEEE Transactions on Aerospace Electronic Systems VL - 8 Y1 - 1972/07/1 SP - 407 EP - 409 UR - https://ui.adsabs.harvard.edu/abs/1972ITAES...8..407S PB - IEEE DO - 10.1109/TAES.1972.309537 SN - 0018-9251 ER - TY - CONF TI - Observations of Soft X-Rays: Two Supernova Remnants in the Constellation Lupus and the Diffuse Background. AU - Palmieri, T. M. AU - Burginyon, G. AU - Hill, R. AU - Seward, F. JO - Bulletin of the American Astronomical Society VL - 4 Y1 - 1972/03/1 SP - 219 UR - https://ui.adsabs.harvard.edu/abs/1972BAAS....4..219P ER - TY - JOUR TI - Limit on Line Emission in the Diffuse X-Ray Background. AU - Toor, A. AU - Price, R. E. AU - Seward, F. D. JO - The Astrophysical Journal VL - 172 Y1 - 1972/03/1 SP - L73 UR - https://ui.adsabs.harvard.edu/abs/1972ApJ...172L..73T N2 - 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. PB - IOP DO - 10.1086/180894 SN - 0004-637X ER - TY - CONF TI - Distance &Absolute Luminosities of Galactic X-Ray Sources. AU - Seward, F. D. AU - Burginyon, G. AU - Grader, R. AU - Hill, R. AU - Palmieri, T. AU - Stoering, J. JO - Bulletin of the American Astronomical Society VL - 4 Y1 - 1972/03/1 SP - 221 UR - https://ui.adsabs.harvard.edu/abs/1972BAAS....4..221S ER - TY - JOUR TI - A Soft X-Ray Survey from the Galactic Center to VELA AU - Hill, R. W. AU - Burginyon, G. AU - Grader, R. J. AU - Palmieri, T. M. AU - Seward, F. D. AU - Stoering, J. P. JO - The Astrophysical Journal VL - 171 Y1 - 1972/02/1 SP - 519 UR - https://ui.adsabs.harvard.edu/abs/1972ApJ...171..519H N2 - 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. PB - IOP DO - 10.1086/151305 SN - 0004-637X ER - TY - JOUR TI - X-Rays from Puppis A and the Vicinity of Vela X AU - Seward, F. D. AU - Burginyon, G. A. AU - Grader, R. J. AU - Hill, R. W. AU - Palmieri, T. M. AU - Stoering, J. P. JO - The Astrophysical Journal VL - 169 Y1 - 1971/11/1 SP - 515 UR - https://ui.adsabs.harvard.edu/abs/1971ApJ...169..515S N2 - 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. PB - IOP DO - 10.1086/151168 SN - 0004-637X ER - TY - JOUR TI - Diffuse Cosmic X-Ray Flux from 0.2 to 2 keV AU - Palmieri, T. M. AU - Burginyon, G. A. AU - Grader, R. J. AU - Hill, R. W. AU - Seward, F. D. AU - Stoering, J. P. JO - The Astrophysical Journal VL - 169 Y1 - 1971/10/1 SP - 33 UR - https://ui.adsabs.harvard.edu/abs/1971ApJ...169...33P N2 - 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. PB - IOP DO - 10.1086/151115 SN - 0004-637X ER - TY - JOUR TI - X-Ray Source Positions for Cygnus X-1, Cygnus X-2, and Cygnus X-3 AU - Toor, A. AU - Price, R. AU - Seward, F. AU - Scudder, J. JO - The Astrophysical Journal VL - 168 Y1 - 1971/08/1 SP - L15 UR - https://ui.adsabs.harvard.edu/abs/1971ApJ...168L..15T N2 - 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. PB - IOP DO - 10.1086/180775 SN - 0004-637X ER - TY - JOUR TI - X-Rays from the Magellanic Clouds AU - Price, R. E. AU - Groves, D. J. AU - Rodrigues, R. M. AU - Seward, F. D. AU - Swift, C. D. AU - Toor, A. JO - The Astrophysical Journal VL - 168 Y1 - 1971/08/1 SP - L7 UR - https://ui.adsabs.harvard.edu/abs/1971ApJ...168L...7P N2 - 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. PB - IOP DO - 10.1086/180773 SN - 0004-637X ER - TY - CONF TI - Soft X-Rays from Vela-X and Puppis A. AU - Seward, F. D. AU - Burginyon, G. A. AU - Grader, R. J. AU - Hill, R. W. AU - Palmieri, T. M. JO - Bulletin of the American Astronomical Society VL - 3 Y1 - 1971/06/1 SP - 393 UR - https://ui.adsabs.harvard.edu/abs/1971BAAS....3Q.393S ER - TY - JOUR TI - Soft X-Rays from Two Supernova Remnants AU - Palmieri, T. M. AU - Burginyon, G. AU - Grader, R. J. AU - Hill, R. W. AU - Seward, F. D. AU - Stoering, J. P. JO - The Astrophysical Journal VL - 164 Y1 - 1971/02/1 SP - 61 UR - https://ui.adsabs.harvard.edu/abs/1971ApJ...164...61P N2 - 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. PB - IOP DO - 10.1086/150815 SN - 0004-637X ER - TY - CONF TI - A Measurement of the Diffuse Cosmic X-Ray Flux from 200 eV-10 keV AU - Burginyon, G. A. AU - Grader, R. J. AU - Hill, R. W. AU - Stoering, J. P. AU - Palmieri, T. M. AU - Seward, F. D. JO - Bulletin of the American Astronomical Society VL - 3 Y1 - 1971/01/1 SP - 20 UR - https://ui.adsabs.harvard.edu/abs/1971BAAS....3R..20B ER - TY - CONF TI - X-Ray Source Survey in the Southern Milky Way AU - Hill, R. W. AU - Burginyon, G. A. AU - Grader, R. J. AU - Stoering, J. P. AU - Palmieri, T. M. AU - Seward, F. D. JO - Bulletin of the American Astronomical Society VL - 3 Y1 - 1971/01/1 SP - 21 UR - https://ui.adsabs.harvard.edu/abs/1971BAAS....3R..21H ER - TY - CONF TI - An X-ray Survey with Large-Area Proportional Counters AU - Price, R. E. AU - Groves, D. AU - Rodrigues, R. M. AU - Seward, F. D. JO - Bulletin of the American Astronomical Society VL - 3 Y1 - 1971/01/1 SP - 22 UR - https://ui.adsabs.harvard.edu/abs/1971BAAS....3R..22P ER - TY - CONF TI - A Large-Area X-Ray Survey AU - Seward, F. D. AU - Burginyon, G. A. AU - Grader, R. J. AU - Groves, D. AU - Hill, R. W. AU - Koppel, L. N. AU - Palmieri, T. M. AU - Price, R. AU - Scudder, J. K. AU - Stoering, J. P. AU - Swift, C. AU - Toor, A. JO - Bulletin of the American Astronomical Society VL - 3 Y1 - 1971/01/1 SP - 22 UR - https://ui.adsabs.harvard.edu/abs/1971BAAS....3...22S ER - TY - JOUR TI - Observation of Galactic X-Ray Sources 1968 November 3 AU - MacGregor, A. AU - Seward, F. AU - Turiel, I. JO - The Astrophysical Journal VL - 161 Y1 - 1970/09/1 SP - 979 UR - https://ui.adsabs.harvard.edu/abs/1970ApJ...161..979M N2 - 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. PB - IOP DO - 10.1086/150598 SN - 0004-637X ER - TY - JOUR TI - Scorpius XR-1: Some X-Ray and Optical Observations (1969 May) AU - Burginyon, G. A. AU - Grader, R. J. AU - Hill, R. W. AU - Price, R. E. AU - Rodrigues, R. AU - Seward, F. D. AU - Swift, C. D. AU - Hiltner, W. A. AU - Mannery, E. J. JO - The Astrophysical Journal VL - 161 Y1 - 1970/09/1 SP - 987 UR - https://ui.adsabs.harvard.edu/abs/1970ApJ...161..987B N2 - 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. PB - IOP DO - 10.1086/150599 SN - 0004-637X ER - TY - JOUR TI - Erratum: the Soft X-Ray Spectra of Three Cosmic Sources and Simultaneous Optical Observations of SCO X-1 AU - Grader, R. J. AU - Hill, R. W. AU - Seward, F. D. AU - Hiltner, W. A. JO - The Astrophysical Journal VL - 160 Y1 - 1970/06/1 SP - 1193 UR - https://ui.adsabs.harvard.edu/abs/1970ApJ...160.1193G PB - IOP DO - 10.1086/150507 SN - 0004-637X ER - TY - JOUR TI - A Measurement of the Optical and X-Ray Emission from Scorpius X-1 and the X-Ray Diffuse Background AU - Toor, A. AU - Seward, F. D. AU - Cathey, L. R. AU - Kunkel, W. E. JO - The Astrophysical Journal VL - 160 Y1 - 1970/04/1 SP - 209 UR - https://ui.adsabs.harvard.edu/abs/1970ApJ...160..209T N2 - 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. PB - IOP DO - 10.1086/150418 SN - 0004-637X ER - TY - CONF TI - Observation of Galactic X-Ray Sources on November 3, 1968 AU - Turiel, I. AU - MacGregor, G. A. AU - Seward, F. D. JO - Bulletin of the American Astronomical Society VL - 2 Y1 - 1970/03/1 SP - 222 UR - https://ui.adsabs.harvard.edu/abs/1970BAAS....2Q.222T ER - TY - JOUR TI - The Soft X-Ray Spectra of Three Cosmic Sources and Simultaneous Optical Observations of SCO XR-1 AU - Grader, R. J. AU - Hill, R. W. AU - Seward, F. D. AU - Hiltner, W. A. JO - The Astrophysical Journal VL - 159 Y1 - 1970/01/1 SP - 201 UR - https://ui.adsabs.harvard.edu/abs/1970ApJ...159..201G N2 - 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. PB - IOP DO - 10.1086/150303 SN - 0004-637X ER - TY - JOUR TI - Soft particle flux above 130 km at midlatitude AU - Hill, R. W. AU - Grader, R. J. AU - Seward, F. D. AU - Stoering, J. P. AD - AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California), AC(Lawrence Livermore National Laboratory, California), AD(Lawrence Livermore National Laboratory, California) JO - Journal of Geophysical Research VL - 75 Y1 - 1970/01/1 SP - 7267 KW - Solar Physics and Astrophysics: X-ray astronomy KW - Particles and Fields in the Ionosphere: X rays UR - https://ui.adsabs.harvard.edu/abs/1970JGR....75.7267H N2 - 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. DO - 10.1029/JA075i034p07267 SN - 0148-0227 ER - TY - JOUR TI - Erratum: Further Simultaneous Observations of the Optical and X-Ray Spectra of SCO X-1 AU - Mark, Hans AU - Price, R. AU - Rodrigues, R. AU - Seward, F. AU - Swift, C. AU - Hiltner, W. JO - The Astrophysical Journal VL - 158 Y1 - 1969/11/1 SP - L131 UR - https://ui.adsabs.harvard.edu/abs/1969ApJ...158L.131M PB - IOP DO - 10.1086/180449 SN - 0004-637X ER - TY - CONF TI - A Simultaneous Measurement of the Optical and X-Ray Emission from Sco X-1 AU - Toor, A. AU - Seward, F. D. AU - Cathy, L. R. AU - Kunkel, W. E. JO - Bulletin of the American Astronomical Society VL - 1 Y1 - 1969/09/1 SP - 365 UR - https://ui.adsabs.harvard.edu/abs/1969BAAS....1R.365T ER - TY - CONF TI - Interstellar Absorption of Crab Nebula X Rays AU - Seward, F. D. AU - Grader, R. J. AU - Hill, R. W. JO - Bulletin of the American Astronomical Society VL - 1 Y1 - 1969/09/1 SP - 361 UR - https://ui.adsabs.harvard.edu/abs/1969BAAS....1S.361S ER - TY - JOUR TI - Further Simultaneous Observations of the Optical and X-Ray Spectra of SCO X-1 AU - Mark, Hans AU - Price, R. E. AU - Rodrigues, R. AU - Seward, F. D. AU - Swift, C. D. AU - Hiltner, W. A. JO - The Astrophysical Journal VL - 156 Y1 - 1969/05/1 SP - L67 UR - https://ui.adsabs.harvard.edu/abs/1969ApJ...156L..67M N2 - 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 PB - IOP DO - 10.1086/180351 SN - 0004-637X ER - TY - JOUR TI - Detection of X-Rays from the Large Magellanic Cloud AU - Mark, Hans AU - Price, R. AU - Rodrigues, R. AU - Seward, F. D. AU - Swift, C. D. JO - The Astrophysical Journal VL - 155 Y1 - 1969/03/1 SP - L143 UR - https://ui.adsabs.harvard.edu/abs/1969ApJ...155L.143M N2 - 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' PB - IOP DO - 10.1086/180322 SN - 0004-637X ER - TY - JOUR TI - A Search for South X-Rays from the Galaxy AU - Grader, R. J. AU - Hill, R. W. AU - Seward, F. D. JO - Sky and Telescope VL - 37 Y1 - 1969/02/1 SP - 79 UR - https://ui.adsabs.harvard.edu/abs/1969S&T....37...79G SN - 0037-6604 ER - TY - JOUR TI - The Soft X-Ray Spectrum of SCO XR-1 AU - Hill, R. W. AU - Grader, R. J. AU - Seward, F. D. JO - The Astrophysical Journal VL - 154 Y1 - 1968/11/1 SP - 655 UR - https://ui.adsabs.harvard.edu/abs/1968ApJ...154..655H N2 - 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 PB - IOP DO - 10.1086/149787 SN - 0004-637X ER - TY - JOUR TI - X-ray airglow in the daytime sky AU - Grader, R. J. AU - Hill, R. W. AU - Seward, F. D. AD - AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California), AC(Lawrence Livermore National Laboratory, California) JO - Journal of Geophysical Research VL - 73 Y1 - 1968/11/1 SP - 7149 EP - 7153 KW - Particles and Fields in the Ionosphere: X rays KW - Particles and Fields in the Ionosphere: Airglow KW - Aeronomy: Atmospheric absorption and scattering of radiation (particles or waves) UR - https://ui.adsabs.harvard.edu/abs/1968JGR....73.7149G DO - 10.1029/JB073i022p07149 SN - 0148-0227 ER - TY - JOUR TI - Simultaneous Observations of the Optical and X-Ray Spectra of SCO XR-1 AU - Chodil, G. AU - Mark, Hans AU - Rodrigues, R. AU - Seward, F. D. AU - Swift, C. D. AU - Turiel, Isaac AU - Hiltner, W. A. AU - Wallerstein, George AU - Mannery, E. J. JO - The Astrophysical Journal VL - 154 Y1 - 1968/11/1 SP - 645 UR - https://ui.adsabs.harvard.edu/abs/1968ApJ...154..645C N2 - 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 PB - IOP DO - 10.1086/149786 SN - 0004-637X ER - TY - JOUR TI - Spectrum of the Central Star in NGC 5189 AU - Blanco, V. AU - Kunkel, W. AU - Hiltner, W. A. AU - Chodil, G. AU - Mark, Hans AU - Rodrigues, R. AU - Seward, F. AU - Swift, C. D. JO - The Astrophysical Journal VL - 152 Y1 - 1968/06/1 SP - L135 UR - https://ui.adsabs.harvard.edu/abs/1968ApJ...152L.135B N2 - 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 PB - IOP DO - 10.1086/180197 SN - 0004-637X ER - TY - JOUR TI - Soft x-Rays from a New Source in the Constellation Vela. AU - Grader, R. J. AU - Hill, R. W. AU - Seward, F. D. JO - The Astronomical Journal Supplement VL - 73 Y1 - 1968/01/1 SP - 179 UR - https://ui.adsabs.harvard.edu/abs/1968AJS....73R.179G N2 - 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. ER - TY - JOUR TI - Simultaneous Observations of the Optical and x-Ray Spectra of SCO XR-1. AU - Hiltner, W. A. AU - Mark, Hans AU - Rodrigues, R. AU - Seward, F. D. AU - Swift, C. D. AU - Turiel, Isaac AU - Chodil, G. AU - Wallerstein, George AU - Mannery, E. J. JO - The Astronomical Journal Supplement VL - 73 Y1 - 1968/01/1 SP - 184 UR - https://ui.adsabs.harvard.edu/abs/1968AJS....73Q.184H N2 - 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. ER - TY - JOUR TI - Diffuse Cosmic X-Ray Background Between 4 and 40 KEV AU - Seward, F. AU - Chodil, G. AU - Mark, Hans AU - Swift, C. AU - Toor, A. JO - The Astrophysical Journal VL - 150 Y1 - 1967/12/1 SP - 845 UR - https://ui.adsabs.harvard.edu/abs/1967ApJ...150..845S N2 - 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. PB - IOP DO - 10.1086/149387 SN - 0004-637X ER - TY - JOUR TI - Search for 8-80 KEV X-Rays from the Large Magellanic Cloud and the Crab Nebula AU - Seward, F. D. AU - Toor, A. JO - The Astrophysical Journal VL - 150 Y1 - 1967/11/1 SP - 405 UR - https://ui.adsabs.harvard.edu/abs/1967ApJ...150..405S N2 - 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. PB - IOP DO - 10.1086/149343 SN - 0004-637X ER - TY - JOUR TI - X-Ray Intensities and Spectra from Several Cosmic Sources AU - Chodil, G. AU - Mark, Hans AU - Rodrigues, R. AU - Seward, F. D. AU - Swift, C. D. JO - The Astrophysical Journal VL - 150 Y1 - 1967/10/1 SP - 57 UR - https://ui.adsabs.harvard.edu/abs/1967ApJ...150...57C N2 - 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). PB - IOP DO - 10.1086/149312 SN - 0004-637X ER - TY - JOUR TI - Spectral and Location Measurements of Several Cosmic X-Ray Sources Including a Variable Source in Centaurus AU - Chodil, G. AU - Mark, Hans AU - Rodrigues, R. AU - Seward, F. AU - Swift, C. D. AU - Hiltner, W. A. AU - Wallerstein, George AU - Mannery, Edward J. AD - 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) JO - Physical Review Letters VL - 19 Y1 - 1967/09/1 SP - 681 EP - 683 UR - https://ui.adsabs.harvard.edu/abs/1967PhRvL..19..681C N2 - 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. PB - APS DO - 10.1103/PhysRevLett.19.681 SN - 0031-9007 ER - TY - JOUR TI - X-Ray Spectra from Three Cosmic Sources AU - Grader, R. J. AU - Hill, R. W. AU - Seward, F. D. AU - Toor, A. JO - Science VL - 152 Y1 - 1966/06/1 SP - 1499 EP - 1504 UR - https://ui.adsabs.harvard.edu/abs/1966Sci...152.1499G N2 - 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. DO - 10.1126/science.152.3728.1499 SN - 0036-8075 ER - TY - JOUR TI - X-Ray Spectra from Scorpius (SCO-XR-1) and the Sun Observed Above the Atmosphere AU - Chodil, G. AU - Jopson, R. C. AU - Mark, Hans AU - Seward, F. D. AU - Swift, C. D. AD - 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) JO - Physical Review Letters VL - 15 Y1 - 1965/10/1 SP - 605 EP - 607 UR - https://ui.adsabs.harvard.edu/abs/1965PhRvL..15..605C PB - APS DO - 10.1103/PhysRevLett.15.605 SN - 0031-9007 ER - TY - JOUR TI - Near-Earth, Polar-Orbiting Satellite Measurements of Charged Particles 1, Instrumentation and Cosmic Rays AU - Seward, F. D. AU - Kornblum, H. N., Jr. JO - Journal of Geophysical Research VL - 70 Y1 - 1965/08/1 SP - 3557 EP - 3570 UR - https://ui.adsabs.harvard.edu/abs/1965JGR....70.3557S N2 - 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. DO - 10.1029/JZ070i015p03557 SN - 0148-0227 ER - TY - CONF TI - Electron Loss Rate from the Outer Radiation Belt AU - Hess, W. N. AU - Bloom, S. D. AU - Mann, L. G. AU - Seward, F. D. AU - West, H. I., Jr. AD - 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) JO - Space Research Conference Y1 - 1963/01/1 SP - 477 UR - https://ui.adsabs.harvard.edu/abs/1963spre.conf..477H ER - TY - JOUR TI - Resonant Scattering of Gamma Rays from Nuclear Levels with a Linear Accelerator AU - Seward, F. D. AD - AA(Lawrence Livermore National Laboratory, California) JO - Physical Review VL - 125 Y1 - 1962/01/1 SP - 335 EP - 340 UR - https://ui.adsabs.harvard.edu/abs/1962PhRv..125..335S N2 - 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. PB - APS DO - 10.1103/PhysRev.125.335 SN - 1536-6065 ER - TY - JOUR TI - Measurement of the Annihilation-in-Flight Cross Section at 0° for 8.5-Mev Positrons AU - Seward, F. D. AU - Hatcher, C. R. AU - Fultz, S. C. AD - AA(Lawrence Livermore National Laboratory, California), AB(Lawrence Livermore National Laboratory, California), AC(Lawrence Livermore National Laboratory, California) JO - Physical Review VL - 121 Y1 - 1961/01/1 SP - 605 EP - 609 UR - https://ui.adsabs.harvard.edu/abs/1961PhRv..121..605S N2 - 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. PB - APS DO - 10.1103/PhysRev.121.605 SN - 1536-6065 ER - TY - JOUR TI - Reaction Mechanism in Inelastic Scattering of Protons from Mg, Cr, and Other Elements from 3.5 to 7 Mev AU - Seward, Frederick D. AD - AA(University of Rochester, New York) JO - Physical Review VL - 114 Y1 - 1959/04/1 SP - 514 EP - 525 UR - https://ui.adsabs.harvard.edu/abs/1959PhRv..114..514S N2 - 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. PB - APS DO - 10.1103/PhysRev.114.514 SN - 1536-6065 ER - TY - Thesis/Dissertation TI - Inelastic Scattering of Protons by Magnesium, Chromium, and Other Elements from 3.5 to 7 Mev. AU - Seward, Frederick Downing AD - AA(University of Rochester, New York) JO - Ph.D. Thesis Y1 - 1959/01/1 KW - Physics: Nuclear UR - https://ui.adsabs.harvard.edu/abs/1959PhDT........22S ER - TY - JOUR TI - Reaction F¹⁹(d, p)F²⁰ and the Spin of F²⁰ AU - Seward, F. D. AU - Slaus, I. AU - Fulbright, H. W. AD - AA(University of Rochester, New York), AB(University of Rochester, New York), AC(University of Rochester, New York) JO - Physical Review VL - 107 Y1 - 1957/07/1 SP - 159 EP - 160 UR - https://ui.adsabs.harvard.edu/abs/1957PhRv..107..159S N2 - 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. PB - APS DO - 10.1103/PhysRev.107.159 SN - 1536-6065 ER - TY - JOUR TI - Discussion on the Origin and Relationship of the British Flora AU - Seward AU - Reid, E. M. AU - Boswell, P. G. H. AU - Chandler, M. E. J. AU - Godwin, H. AU - Wilmott, A. J. AU - Salisbury, E. J. AU - Raistrick, A. AU - Du Rietz, G. Einar AU - Watson, W. AU - Simpson, G. C. AU - Dewey AU - Simpson, J. B. AU - Sandford, K. S. AU - Butcher, R. W. AU - Wright, W. B. AU - Hamshaw Thomas, H. AU - Burkitt, Miles AU - Burtt Davy, J. AU - Turrill, W. B. AU - Watt, Alex S. AU - Hollingworth JO - Proceedings of the Royal Society of London Series B VL - 118 Y1 - 1935/08/1 SP - 197 EP - 241 UR - https://ui.adsabs.harvard.edu/abs/1935RSPSB.118..197R DO - 10.1098/rspb.1935.0054 SN - 0080-46490962-8452 ER -