On the radial dependence of the disk FeK alpha line emissivity in active galactic nuclei

The iron K alpha fluorescent line detected in many Seyfert 1 galaxies by AS CA and BeppoSAX is usually considered to arise in the innermost region of a n accretion disk around a supermassive black hole. The line profile is usua lly modelled by assuming that the disk emissivity follows a power law, epsi lon(R)proportional to R-q. We present a new technique to invert the line pr ofile and infer: (a) the free-format epsilon(R), (b) the disk inclination t o the line of sight and (c) the black hole angular momentum. The applicatio n of this technique to published K alpha data shows that the line shapes ar e consistent with the accretion disk model and that the major contribution to the emissivity comes from the innermost disk regions. We also show that a sharp distinction between different black hole angular momenta can usuall y not be made on the basis of present data. (C) 2000 Elsevier Science B.V. All rights reserved.