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| Paper: |
Chandra Spectra of Thermal Emission from Neutron Stars |
| Volume: |
271, Neutron Stars in Supernova Remnants |
| Page: |
327 |
| Authors: |
Stage, M. D.; Joss, P. C.; Madej, J. |
| Abstract: |
We present Chandra ACIS and zeroth order HETG/ACIS-S spectra of the Cas A point source extracted from a 50-ksec imaging and a 70-ksec grating observation of the Cas A supernova remnant. There is mounting evidence that the point source is a thermally emitting neutron star. We fit the ACIS spectra with the latest hydrogen / helium models produced by the new ATM model atmosphere code developed by Paul Joss and Jurek Madej. The ATM code calculates the emergent spectrum from a neutron star atmosphere of specified effective temperature and surface gravity. We have previously carried out model atmosphere fits to a spectrum extracted from the archival Chandra 50-ksec observation (ObsID 114). Here we combine this data with a 70-ksec Chandra High Energy Transmission Grating/ACIS-S (HETG) observation of the X-ray point source (XPS) to simultaneously fit the largest number of ACIS spectra photons from the XPS to date. Our superior ATM model atmosphere fits yield surface effective temperatures of ~4.1 MK, a surface emission patch size of ~1.8 km, and a stellar radius of ~6.5 km. We present the results of fitting power law, blackbody and our hydrogen/helium model atmospheres. In our fits, we correct for the presence of absorption features in the spectrum created by silicon and sulfur along the line of sight, as well as general relativistic effects to calculate the temperature, radius of the star, and radius of the emitting region. |
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