Complex absorption and reflection of a multitemperature cyclotron-bremsstrahlung X-ray cooling shock in BY Cam
Abstract
We re-analyse the ASCAGinga X-ray data from BY Cam, a slightly asynchronous magnetic accreting white dwarf. The spectra are strongly affected by complex absorption, which we model as a continuous (power-law) distribution of covering fraction and column of neutral material. This absorption causes a smooth hardening of the spectrum below ~3keV, and is probably produced by material in the pre-shock column which overlies the X-ray emission region. The ASCA data show that the intrinsic emission from the shock is not consistent with a single-temperature plasma. Significant iron L emission coexisting with iron K shell lines from H- and He-like iron clearly shows that there is a wide range of temperatures present, as expected from a cooling shock structure. The Ginga data provide the best constraints on the maximum temperature emission in the shocked plasma, with kTmax=21+18-4keV. Cyclotron cooling should also be important; it suppresses the highest temperature bremsstrahlung components, so the X-ray data provide only a lower limit on the mass of the white dwarf of M>=0.5Msolar. Reflection of the multitemperature bremsstrahlung emission from the white dwarf surface is also significantly detected. We stress the importance of modelling all these effects in order to gain a physically self-consistent picture of the X-ray spectra from polars in general and BY Cam in particular.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- August 1998
- DOI:
- 10.1046/j.1365-8711.1998.01636.x
- arXiv:
- arXiv:astro-ph/9712226
- Bibcode:
- 1998MNRAS.298..737D
- Keywords:
-
- accretion;
- accretion discs;
- binaries: close;
- stars: individual: BY Cam;
- novae;
- cataclysmic variables;
- X-rays: stars;
- Astrophysics
- E-Print:
- 9 pages, 4 figures, MNRAS, accepted