Abstract
The principal results on active galactic nuclei obtained by the Oriented Scintillation Spectrometer Experiment (OSSE) on the COMPTON Gamma Ray Observatory are presented. These include observations of 26 Seyfert galaxies in lowenergy gamma rays and observations of several of the high-energy gamma ray sources detected by EGRET. OSSE observes a thermal-like spectrum from NGC 4151, and the average gamma ray spectrum of weak Seyferts is significantly softer (consistent with a 45 keV thermal spectrum) than the spectrum below 50 keV. OSSE has not detected any positron annihilation radiation from any Seyfert, and has not detected an MeV excess from these sources. The OSSE observations of several blazars, when combined with the COMPTEL and EGRET data, indicate that the spectral characteristics of these sources vary dramatically, exhibiting power-law spectra with breaks or changes in spectral index in the MeV region which vary from 0 to greater than 1.
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