OPTICS NEAR KERR BLACK-HOLES - SPECTRA OF ADVECTION DOMINATED ACCRETION FLOWS

We investigate advection dominated accretion flows of matter in the vi cinity of black holes, using the fully relativistic description in the frame of disk approximation. We also include some effects of the quas i-sphericity of the Bow. We are interested in the spectra emitted by s uch Bows and specifically, in the relativistic effects accompanying pr opagation of light. Using the ray shooting method in the Kerr metric w e calculate the spectra of three different accretion flows. We also ca lculate the shape of a gamma-ray line which could be formed in the flo w, assuming that it has a natural Doppler profile. We find that effect s of relativistic optics may influence the isotropy of the radiation a nd that observers close to the equatorial plane would measure a higher source luminosity. The line is strongly broadened, but the fact that the flow is quasi-spherical removes two-peak shape of the line charact eristic for the spectra emitted from thin, Keplerian disks. The kinema tics of the advection dominated Bows is not unique (as opposed to Kepl erian disks or spherical free-fall) and it would be probably difficult to find strong limits on source models using the spectral observation s.