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| Paper: |
X-ray Heated Black Hole Accretion Discs |
| Volume: |
330, The Astrophysics of Cataclysmic Variables and Related Objects |
| Page: |
219 |
| Authors: |
Wickramasinghe, D.; Hubeny, I. |
| Abstract: |
The response of the disc to external irradiation depends on the importance of the irradiation flux relative to the viscous flux, and on the details of the incident spectrum; the higher energy photons will preferentially Compton scatter and heat/cool the disc, while the lower energy photons will be mainly photo absorbed and re-emitted. Irradiation with a black body spectrum at temperatures appropriate to the inner regions of the disc generally results in a temperature inversion in the upper disc atmosphere at all disc radii. A general characteristic of all models is that as the irradiation flux increases relative to the viscously generated flux, and the effects of heating penetrates to the disc mid plane, the temperature profile at large optical depths becomes flatter. In addition, irradiation reduces the continuum jumps and makes the spectrum more black body like. For moderate irradiation, a Compton reflection peak develops at frequencies corresponding approximately to the peak of the irradiating flux. This is seen as a flux excess over the thermal emission that would normally be expected from the heated disc if the effects of scattering were ignored. In the limit of strong irradiation, a saturated inverse Compton spectrum develops with a high energy Wien tail. The detection of a Compton reflection peak, and a study of its spectral characteristics, will provide a strong diagnostic on the nature of the irradiating source. Hα line profiles are also presented. |
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