IRON K-ALPHA LINE FROM X-RAY ILLUMINATED RELATIVISTIC DISKS

The intensity and profile of the iron K-alpha fluorescence line from a flat, optically thick accretion disk rotating around a Schwarzschild black hole and illuminated by a central X-ray source are computed using a fully relativistic treatment of the photon intensity and shifts. The X-ray source is modelled as an isotropic point source located on the symmetry axis at a height h in units of the gravitational radius. These calculations represent a refinement and an extension of those presented in Paper I for h = 20, carried out using a weak field approximation and therefore of validity limited to inclination angles less-than-or-similar-to 70-degrees. Here it is shown that at high inclination angles purely relativistic effects lead to the growth of features between the two Doppler horns and that, as a consequence, the line equivalent width maintains a sizeable value, while the centroid energy and the line width go through a broad maximum at about approximately 80-degrees. The statistical implications for the expected distribution of the line parameters in a sample of randomly oriented disks in Seyfert galaxies are briefly discussed.