Hard X-ray observations of cosmic γ-ray sources

THE publication¹, by workers using the COS B satellite, of a list of 13 discrete cosmic γ-ray sources has aroused considerable interest. Attention has mainly been focussed on attempts to identify all or some of these sources with known X-ray sources^2-4, optical sources^5,6, radio sources⁷ and HII regions⁸. In most cases the large COS B error boxes have made this a difficult task. We report here on hard X-ray studies of these γ-ray error boxes and suggest that unresolved sources of this type could account for the galactic disk γ-ray emission.