The origin of the X-ray background

Satellite observations of cosmic X ray radiation as a means to discerning discrete, as opposed to diffuse, sources of the emissions are reviewed. HEAO 1 data of the X ray background (XRB) from 3-50 keV, HEAO 1-A2 all sky survey data from 2-10 keV, and Einstein Observatory readings from 0.3-3.5 keV are examined for evidence of the total contribution of discrete sources to the observed XRB. Correlations are made among X ray, optical, and radio luminosities in quasars and Seyfert galaxies. The discrete sources are found to account for at most 60% of the observed emissions, with, however, a large uncertainty. Improvements in the capability of detecting radioquiet quasars are indicated in the launch of the X ray satellite Rosat in 1986. Detection of X ray sources down to magnitude 20 will then be possible.