OBSERVATIONS OF A COSMIC GAMMA-RAY BURST ON 23 JULY 1992 WITH THE WATCH INSTRUMENT ON THE GRANAT OBSERVATORY

The cosmic gamma-ray burst detected by the Granat observatory on 23 Ju ly 1992 at 20h03m08s.377 (UT) is one of the brightest events observed during its operation, beginning in December 1989. That burst was detec ted by three burst instruments on the observatory (PHEBUS, SIGMA, and WATCH). Below we give data from the WATCH Russian-Danish experiment on locating the source of the burst, the light curve in various energy r anges, and the evolution of the hardness of the radiation. We show tha t the source of the gamma-ray burst emitted a fading x-ray flux with a characteristic temperature approximately 5 keV, in the approximation of a blackbody spectrum, for more than 40 sec after the burst ended in hard x rays. We give the limits on the luminosity of a steady source at the site of the burst in the 8-20 keV range. We show that the flux from a steady source at the site of the burst did not exceed 20 mCrab for at least several days before and after the event.