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J. Poutanen (Stockholm Observatory)
Observations show that accretion disks in many X-ray binaries are flared. The outer edge of the disk intercepts radiation from the central X-ray source. Part of that radiation is absorbed and reemitted in the optical and UV spectral range. However, a large fraction of that radiation is reflected from the disk and appear in the broad-band X-ray spectrum as a Compton reflection bump. This radiation is delayed and smeared comparing with the intrinsic X-ray radiation. We compute transfer functions expected from isotropic and anisotropic X-ray sources in flat and flared accretion disks. We further study the impact of the reprocessing on the temporal characteristics of X-ray binaries such as power spectral density, auto- and cross-correlation functions, and Fourier frequency dependent time/phase lags, and compare our simulations with the data. We propose the model for the reprocessing which explains the breaks in the time lag Fourier spectrum observed in Cyg X-1 and other Galactic black hole sources. Possible tests of the model are presented.