The Spectrum of Diffuse Cosmic X-Rays Observed by OSO-3 Between 7 and 100 KEV

The shape of the diffuse X-ray spectrum in the 1-100 keV range has important implications regarding its origin and its possible connection with the diffuse y-rays measured at higher energies. Previous results have suggested that the spectrum decreases with energy more rapidly in the keV interval than in the 2-10 keV interval. However, the OSO-3 X-ray detector, covering the 7.7-210 keV range with an area of 9.57 cm2, and collimated to a 12 half-angle field of view, has provided the only data from a single instrument which could not be fitted by a single power-law spectrum even over the limited range of that instrument. In this paper we consider the effects of long-lived induced radioactivity, energy dependence of the effective aperture, and fluorescence radiation from the shield on our previous estimate of the diffuse X-ray counting rates observed from OSO-3. We confirm our previous conclusion that the spectral data cannot be represented by a single power-law function. A sharp discontinuity between two power-law indices suffices for a minimum-parameter representation of the data. However, our results are also consistent with a continuous change of slope between 7 and 100 keV. Subject headings: spectra, X-ray - X-rays - cosmic background radiation