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Published online by Cambridge University Press: 14 August 2015
Recent observations by the Einstein Observatory have shown that a majority of known quasars are powerful X-ray emitters. The 107 objects observed as of Feb. 1980 (Zamorani et al. 1980) have X-ray, optical and radio luminosities scattered over a wide range. Until a large enough X-ray selected sample of quasars becomes available, it is necessary to study statistical correlations in the available sample, so that some insight into X-ray production may be obtained, and the contribution of quasars to the X-ray background estimated.