Detection of High-Energy Gamma Rays from Quasar PKS 0528+134 by EGRET on the Compton Gamma Ray Observatory

The first several pointing directions of the Compton Gamma Ray Observatory, launched on 1991 April 5, were toward the Galactic anticenter. In addition to the known gamma-ray sources, Crab (PSR 0531 + 21) and Geminga (2CG 195+04), high-energy gamma-ray emission (30 MeV to over 1 GeV) was observed from the quasar PKS 0528 + 134 by the Energetic Gamma Ray Experiment Telescope (EGRET). A redshift measurement, reported here, of 2.07 confirms the identification of this object as a quasar. The differential photon spectrum is well represented by a power law with an exponent of 2.56 +/- 0.09 and a photon intensity above 100 MeV of (8.4 +/- 1.0) x 10^-7^ photons cm^-2^ s^-1^. There is evidence for time variability on a time scale of a few days.