X-ray irradiated model stellar atmospheres - III. Compton redistribution of thermal external irradiation
Abstract
In this paper we present and solve full set of model atmosphere equations, corresponding to a compact star illuminated by hard external X-rays. Our equations include effects of multiple Compton scattering of radiation on free electrons in relativistic thermal motion, and rich set of bound-free and free-free monochromatic opacities. We allow for a large relative photon-electron energy exchange at the time of Compton scattering, and therefore we are able to reconstruct Compton scattering of photons with energy exceeding the electron rest mass. Our numerical results show that hard external X-rays lose energy significantly and move to softer spectral bands after backscattering from a colder gas. We demonstrate, that outgoing spectra of irradiated atmospheres exhibit a soft X-ray excess in the range below 1 keV, similar to the one observed in most broad-band continuum spectra of active galactic nuclei.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- February 2004
- DOI:
- 10.1111/j.1365-2966.2004.07310.x
- Bibcode:
- 2004MNRAS.347.1266M
- Keywords:
-
- radiative transfer;
- scattering;
- quasars: general;
- X-rays: general;
- X-rays: stars