Observations of Seyfert galaxies by OSSE and parameters of their X-ray/gamma-ray sources

We present a summary of spectra of Seyfert galaxies observed by the OSSE detector aboard Compton Gamma Ray Observatory. We obtain average spectra of Seyfert galaxies of types 1 and 2 and find they are well fitted by thermal Comptonization. We present detailed parameter ranges for the plasma temperature and the Compton parameter in the cases of spherical and slab geometries. We find both the average and individual OSSE spectra of Seyfert 2s are significantly harder than those of Seyfert Is, which difference can be due to anisotropy of Compton reflection and/or Thomson-thick absorption.