An X-ray illuminated disc in Kerr metric

If the primary source, assumed to be isotropic in its own reference frame, is very close to the BH (i.e. h is small), the illuminating photons' trajectories are strongly bended by the spacetime curvature. The illuminating flux is thus very anisotropic, and the emission is concentrated in the innermost part of the disc. With decreasing h, the effect of light bending, i.e. the anisotropy, increases  (cp. Figure 1). This causes a substantial increase of the fluorescent and  Compton-reflected components, and a decrease of the primary continuum.

The emissivity is derived by means of fully relativistic calculations of the primary flux impinging onto the disc (Martocchia & Matt 1996, 1997; Martocchia, Karas & Matt, 2000). Results on the iron line profiles and underlying Compton-reflected continuum have been presented by Martocchia, Karas & Matt (2000).