The nature of the X-ray source in NGC 4151.

Analysis of broad-band X/γ-ray spectra of NGC 4151 shows that the data are well modelled with an intrinsic spectrum due to thermal Comptonization with temperature ≡50 keV and X-ray spectral index α ≡ 0.4-0.7. The variable X-ray spectrum pivots at ≡100 keV, which is consistent with the observed approximately constant γ-ray spectrum. The observed UV/X-ray correlation can be explained by two specific models with reprocessing of X-rays by cold matter. The first one is based on reemission of the X-ray flux absorbed by clouds in the line of sight. The second assumes reprocessing of X-rays and γ-rays by a cold accretion disk with a dissipative patchy corona.