Why Do Some Intermediate Polars Show Soft X-Ray Emission? A Survey of XMM-Newton Spectra
Abstract
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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2007
- DOI:
- 10.1086/518552
- arXiv:
- arXiv:0704.1388
- Bibcode:
- 2007ApJ...663.1277E
- Keywords:
-
- Accretion;
- Accretion Disks;
- Stars: Novae;
- Cataclysmic Variables;
- X-Rays: Binaries;
- Astrophysics
- E-Print:
- 9 pages, 6 figures. Accepted for publication in ApJ