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M.D. Stage (MIT Center for Space Research), P.C. Joss (MIT), J. Madej (Warsaw University)
We present new results of fitting Chandra ACIS and LETG/HRC-S spectra of the Cas A X-ray point source and the recent archival DDT observation of neutron star RXJ185635-3754 to hydrogen and iron atmosphere models calculated with our ATM model atmosphere code (Stage, Joss, & Madej, 2001, Neutron Stars in Supernova Remnants, in press). We present the radii and surface temperatures of the sources. The ATM code uses a virtually exact quantum electrodynamical treatment of incoherent Compton scattering to generate model spectra for given composition, surface gravity and temperature. Observed spectra are then fit to a multidimensional grid of model spectra parameterized by the neutron star's effective temperature, radii, mass, and surface composition, taking into account both general relativistic and instrumental effects. In the case of Cas A, we discuss and fit the effects of supernova remnant shell material, specifically Si and S, on the the observed spectrum. As our emphasis is on the physical interpretation of the derived parameters, we will discuss the significance of our self-consistent fit-determined radii, masses, and redshifts on the present theoretical understanding of these objects. In particular, for the Cas A point source, we examine the implications of our hydrogen atmosphere results, which indicate an object radius of approximately 6.5 km, but a radiating area scale size of only 2 km at an effective temperature of 4.1 MK.
The author(s) of this abstract have provided an email address for comments about the abstract: mikstage@space.mit.edu
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.