Models of disk atmospheres irradiated by hard x-rays Original Research Article

We present calculations of LTE model atmospheres of some ring on the accretion disk, which are illuminated by isotropic hard X-rays. We assume both hydrostatic and radiative equilibrium plus Compton scattering by free electrons. Our models take into account also b-f and f-f opacity of hydrogen, helium, and iron in all ionization states. Radiative transfer is solved with the method of variable Eddington factors. We have computed series of model atmospheres for a ring of the radius 10RSchw, rotating around the black hole of M = 108M⊙ in the center of an active galactic nucleus (AGN). Outgoing spectra, from infrared to X-rays, exhibit all the three components: thermal radiation of the disc, reflected and comptonized external X-ray blackbody radiation, and thermal radiation from the uppermost layers, heated to very high temperatures. Theoretical spectra show He i and He ii Lyman opacity jumps, and numerous b-f jumps of highly ionized iron, all of them in emission. We demonstrate that in all considered atmospheres the external illumination by X-rays very strongly reduces the H i Lyman edge.