SPECTRAL SHIFTS OF RADIATION FROM THE VICINITY OF BLACK-HOLES

We are looking for possible methods of estimating black hole angular m omenta. We consider the shapes of the spectral lines emitted by the th in accretion disks. We also investigate the spectra of hypothetical ga mma lines from advection dominated accretion flows. We find the maxima l blueshift of radiation emitted by a source passing close to the blac k hole. Theoretically the best method of measuring black hole spin wou ld be the observation of test particles in their vicinity: the maximal blueshift of radiation can be higher for a hole with large spin. Obse rvationally the best method is probably the study of the iron fluoresc ent lines from cold accretion disks in some objects.