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Why do some intermediate polars show soft X-ray emission? A survey of XMM-Newton spectra

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journal contribution
posted on 24.10.2012, 09:06 by P. A. Evans, C. Hellier
We make a systematic analysis of the XMM-Newton X-ray spectra of intermediate polars (IPs) and find that, contrary to the traditional picture, most show a soft blackbody component. We compare the results with those from AM Her stars and deduce that the blackbody emission arises from reprocessing of hard X-rays, rather than from the blobby accretion sometimes seen in AM Hers. Whether an IP shows a blackbody component appears to depend primarily on geometric factors: a blackbody is not seen in those that have accretion footprints that are always obscured by accretion curtains or are only visible when foreshortened on the white-dwarf limb. Thus we argue against previous suggestions that the blackbody emission characterizes a separate subgroup of IPs that are more akin to AM Hers, and develop a unified picture of the blackbody emission in these stars.

History

Citation

Astrophysical Journal, 2007, 663 (2), pp. 1277-1284

Version

VoR (Version of Record)

Published in

Astrophysical Journal

Publisher

American Astronomical Society (IOP Publishing)

issn

0004-637X

eissn

1538-4357

Copyright date

2007

Available date

24/10/2012

Publisher version

http://iopscience.iop.org/0004-637X/663/2/1277/

Language

English