The Direction and Spectral Variability of a Cosmic Gamma-Ray Burst

We report the simultaneous observations of a -ray event with six different X-ray and -ray instruments: (1) the Los Alamos -ray detectors on three Vela satellites; (2) the GSFC solar-flare -ray detector on the IMP-6 satellite; (3) two UCSD X-ray telescopes on board the 050-7. This event was observed from 7 to 1500 keV. Eight spectra at 10.24-s intervais were determined over the 11-100 keV range; power-law (F E-a photons cm-2 -1 keV-1) spectra with a from .77 to 1.5 fit the data over this range. The highest intensity intervals have the flattest spectra. The total energy of the event ( 80 5 duration) was 5 X 10- ergs cm-2. The direction of the event was unambiguously determined from the UCSD cosmic X-ray telescope with a 90 percent confidence, 4 error radius, as a - This was in agreement with one of two possible directions determined independently by the Vela satellites which was a = 172 - 77 with a 90 percent confidence error radius. Subject heading: gamma rays