SEARCH FOR EXTENDED HARD GAMMA-RAY EMISSION IN GRBS

The PHEBUS instrument aboard the GRANAT observatory is able to record spectra of gamma-ray bursts in a broad energy range from 0.1 to 100 Me V. Over 180 bursts were observed by PREBUS during five years of operat ion. They represent a very rich sample of events widely differing in d urations, light curves and energy spectra. The problem of burst behavi our in the decay phase of the GRB events is discussed in this paper. W e present here the results of the search for emission from GRB sources in 100 keV - 100 MeV range after the main burst has finished. Presenc e of extended emission was found in about 10% of the gamma-ray bursts detected by PHEBUS.