Models of the iron Kα fluorescent line and the Compton Shoulder in irradiated accretion disc spectra

We present a full set of model atmosphere equations for the accretion disc around a supermassive black hole irradiated by a hard X-ray lamp of power-law spectral distribution. Model equations allow for multiple Compton scattering of radiation on free electrons, and for large relative photon-electron energy exchange at the time of scattering. We present spectra in specific intensities integrated over the disc surface. Theoretical outgoing intensity spectra show soft X-ray excess below 1 keV, and distinct K alpha and K beta fluorescent lines of iron. We demonstrate the existence of the Compton Shoulder and claim that it can contribute to the asymmetry and equivalent widths of some observed Fe K alpha lines in active galactic nuclei. Our models exhibit the effect of limb-brightening in reflected X-rays.