EGRET OBSERVATIONS OF GREATER-THAN-30-MEV EMISSION FROM THE BRIGHTEST BURSTS DETECTED BY BATSE

EGRET on the Compton Gamma Ray Observatory has detected 5 gamma-ray bursts above 30 MeV. The sub-MeV emission, as detected by BATSE, for these 5 bursts has the largest fluence, F, and peak intensity, I, of any of the BATSE detected bursts within the EGRET field of view. The BATSE data reported in the 2B catalog and the EGRET exposure, E, are combined to select additional bursts with large F x E and I x E. The EGRET data for these bright BATSE bursts are searched for prompt, as well as delayed, emission above 30 MeV. The average properties of the >30 MeV emission are obtained by adding the EGRET data from the 5 bursts. On average the fluence is greater than 15% of the fluence detected by BATSE below an MeV, and the average spectrum is flatter than the spectrum from 1-30 MeV.