THE EGRET DETECTION OF QUASAR-1633+382

In the course of a full-sky survey, the EGRET instrument aboard the Compton Observatory detected an intense, high Galactic latitude source (GRO J1635+38), which is identified as OVV (optically violent variable) quasar 1633+382. The spectrum is represented by a power law with an energy spectral index of 0.9 between 30 MeV and 30 GeV. The gamma-ray power per decade is approximately 100 times larger than typical values at any longer wavelength. Significant variation of the gamma-ray flux density on a time scale as short as 2 days was observed, limiting the size of the region in which the gamma-rays are produced. Assuming the X-rays detected by the Einstein Observatory from this quasar are produced in the same region as the gamma-rays, and a similar X-ray flux density was extant at the time of the EGRET observation, the emission must be beamed to avoid a pair-production optical depth of approximately 10(4) which would exist otherwise. If beaming arises from bulk relativistic motion, the minimum Doppler factor required is 7.6.