Comptonization signatures in the rapid aperiodic variability of galactic black hole candidates

We investigate the effect of Compton scattering of flares of soft radiation in different geometries of a hot, Comptonizing region and a colder accretion disk around a solar mass black hole. The photon energy-dependent light curves, their Fourier transforms, power spectra, and Fourier period-dependent time lags of hard photons with respect to softer photons are discussed. On the basis of a comparison with existing data we find arguments against Comptonization of external soft radiation as well as Comptonization in a homogeneous medium as dominant mechanisms for the rapid aperiodic variability in Galactic black hole candidates. Possible further observational tests for the influence of Comptonization on the rapid aperiodic variability of Galactic black hole candidates are suggested.