GAMMA-RAY OBSERVATIONS IN THE GALACTIC-CENTER REGION WITH AN IMAGING DETECTOR

Results of a series of experiments to detect gamma-ray emission greate r than 10 MeV from the Galactic plane near the Galactic center are rep orted. Three low-background observations of the Galactic center region were made from high-altitude balloon platforms at similar to 12 GV ge omagnetic cutoff rigidities in 1971 and 1975. A 3 degrees wide band of emission along the plane was detected near the center which shows clu stering on the 1 degrees scale of the instrument's resolution. A signi ficant part of this narrow band of emission is either from a concentra ted region of diffuse emission between 350 degrees and 0 degrees Galac tic longitude or from up to five discrete sources. Support for this di screte source interpretation comes from the fact that five of the seve n most significant event concentrations correlate in position with liv e of the seven previously detected hard X-ray and higher energy gamma- ray sources in the Galactic center region.