Intense gamma radiation has been observed from the direction of the quasar 3C 279 throughout the energy range from 30 MeV to over 5 GeV by the Energetic Gamma Ray Experiment Telescope (EGRET) during the period 1991 June 15-28. Its spectrum is well represented by a photon differential power-law exponent of 2.0+/-0.1, with a photon intensity above 100 MeV of (2.8 +/- 0.4) x 10^6^ cm^-2^ s^-1^. 3C 279 was not detected by either of the earlier high-energy gamma-ray telescopes SAS 2 or COS B. For E > 100 MeV, the 2 σ upper limits were 1.0 x 10^-6^ cm^-2^ s^-1^ in 1973 from the SAS 2 observations and 0.3 x 10^-6^ cm^-2^ s^-1^ for the combined 1976, 1978, and 1980 COS B observations. Hence, there has been a large increase in high-energy gamma-ray intensity relative to the earlier times, as there has been in the radio, infrared, optical, and X-ray ranges. This source is the most distant and by far the most luminous gamma-ray source yet detected.
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Hartman et al. (1992) studied this question.