Optics near Kerr black holes: spectra of advection dominated accretion flows

We investigate advection dominated, transsonic accretion flows in the of a Kerr black hole. We take into account all relativistic effects in dynamics of the flow and in the propagation of light. We assume the matter be weakly magnetized and cool via the thermal synchrotron and Bremsstrahlung. We include also the effects of Comptonization. We calculate the of radiation as seen by observers located at different positions to the equatorial plane of the disk. The radiation emitted by the matter is anisotropic and observers near the equatorial plane a higher energy flux. This effect is more pronounced in the case of rotating black holes. We calculate also the shape of a hypothetical line, which may be produced by the thermonuclear reactions in the inner of the flow. The line is strongly broadened, but the fact that the flow is-spherical removes the two-peak shape of the line seen in the spectra from thin, Keplerian disks. The kinematics of the advection dominated is not unique (as opposed to Keplerian disks or spherical free-fall) and would probably be difficult to find strong limits on source models using the observations.