Anisotropic illumination of AGN's accretion disk by a non thermal source II: General relativistic effects

Abstract

In a previous paper (Henri & Petrucci, hereafter paper I), we have derived a new model in order to explain the UV and X-ray emission of radio quiet AGNs. This model assumes that a point source of relativistic leptons (e+,e-) illuminates the accretion disk of the AGN by Inverse Compton process. This disk is supposed to be simply represented by a finite slab which radiates only the energy reprocessed from the hot source. The radiation field within the hot source region is therefore highly anisotropic, which strongly influences the Inverse Compton process. The different Eddington parameters characterizing the radiative balance of this system have been calculated self-consistently in the Newtonian case (paper I) giving a universal spectrum for a given inclination angle. In this paper, we take into account relativistic effects by including the gravitational redshift, the Doppler boosting and the gravitational focusing due to the central supermassive black hole. This has the effect of modifying the radial temperature profile in the innermost region of the disk (at some gravitational radii). However, the spectrum is hardly different from that obtained in the Newtonian case, unless the hot source is very close to the black hole. These results are clearly different from standard accretion disk models where the gravitational energy is mainly released in the vicinity of the black hole.