Correlation between Compton reflection and X-ray slope in Seyferts and X-ray binaries

Abstract

We find a very strong correlation between the intrinsic spectral slope in X-rays and the amount of Compton reflection from a cold medium in Seyfert AGNs and in hard state of X-ray binaries with either black holes or weakly-magnetized neutron stars. Objects with soft intrinsic spectra show much stronger reflection than ones with hard spectra. We find that at a given spectral slope, black-hole binaries have similar or more reflection than Seyferts whereas neutron-star binaries in our sample have reflection consistent with that in Seyferts. The existence of the correlation implies a dominant role of the reflecting medium as a source of seed soft photons for thermal Comptonization in the primary X-ray source.