TEMPORAL AND SPECTRAL PROPERTIES OF COMPTONIZED RADIATION AND ITS APPLICATIONS

We have found relations between the temporal and spectral properties o f radiation Comptonized in an extended atmosphere associated with comp act accreting sources. We demonstrate that the fluctuation power spect rum density (PSD) imposes constraints on the atmosphere scale and prof ile. Furthermore, we indicate that the slope and low-frequency break o f the PSD are related to the Thomson depth, tau(0), of the atmosphere and the radius of its physical size, respectively. Since the energy sp ectrum of the escaping radiation also depends on tau(0) (and the elect ron temperature kT(e)), the relation between spectral and temporal pro perties follows. This relation allows, for the first time, an estimate of the accreting matter Thomson depth, tau(0), independent of argumen ts involving Comptonization. We present figures for the light curves a nd PSDs of different energy bands, the photon energy spectra, and the phase lags as functions of the variability frequency. The temporal pro perties of the high (soft) and low (hard) state of black hole sources are discussed in this context.