GENERALIZED COMPTONIZATION MODELS AND APPLICATION TO THE RECENT HIGH-ENERGY OBSERVATIONS

The theory of spectral formation in thermal X-ray sources, where the e ffects of Comptonization and Klein-Nishina corrections are important, is presented. Analytical expressions are obtained for the produced spe ctrum as a function of such input parameters as the plasma temperature , the optical depth of the plasma cloud and the injected soft photon s pectrum. The analytical theory developed here takes into account the d ependence of the scattering opacity on the photon energy. It is shown that the plasma temperature as well as the asymptotic rate of photon e scape from the plasma cloud determine the shape of the upscattered har d tail in the emergent spectra, even in the case of very small optical depths. The escape distributions of photons are given for any optical depth of the plasma cloud and their asymptotic dependence for very sm all and large optical depths are examined. It is shown that this new g eneralized approach can fit spectra for a large variety of hard X-ray sources and determine the plasma temperature in the region of main ene rgy release in Cyg X-1 and the Seyfert galaxy NGC 4151.