QSO Optical Counts and Constraints on the X-Ray Background

The optical and the X-ray properties of optically selected quasars are used to predict the soft X-ray source counts in the Einstein Imaging Proportional Counter (IPC) band. The optical quasar counts and the published alpha_0x relations do not reproduce the observed X-ray source counts. The predicted counts exceed the observations by factors of five to fifty. These excesses arise from the low luminosity, low redshift active galactic nuclei, redshift range characterizing the optical sample. It is concluded that quasars cannot be major contributors to the soft X-ray background.