The fluctuating and isotropic components of the cosmic X-ray background

Spatial fluctuations in the surface brightness of the extragalactic hard X-ray sky that are characteristic of distant unresolved discrete sources as well as the possible clumpiness of a hot universal plasma are being studied with the HEAO-1 A-2 experiment. The energy spectrum for this fluctuating component is directly compared to that of the isotropic background. The spectra of identified extragalactic objects recently obtained with experiments aboard both OSO-8 and HEAO-1 are used for examining the contribution of such sources to this fluctuating component of the background.