The origin of the x-ray spectra of AGN

Abstract

The presence of a spectral component due to Compton reflection in the X-ray spectra of AGN, as recently observed by Ginga, give new clues to the properties of the central regions of these sources. These observations revive models in which much of the luminosity generated in X- and γ-ray energy bands in AGN is reprocessed via electron-positron pairs. In these models the X-ray spectral index is α _ξ ≃- 1 for a wide range of parameters. If a substantial fraction of this radiation is incident upon cold material, the composite (directly observed + reflected) spectrum has an average spectral index of α _ξ ≃- 0.7 in the 1–30 keV band, and steepens above ~ 1 MeV. Such spectra agree well with the X-ray and γ-ray observations of AGN and the constraints imposed by the cosmic γ-ray background.