A possible very high energy gamma-ray burst from Hercules X-1

Abstract

view Abstract Citations (15) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Possible Very High Energy Gamma-Ray Burst from Hercules X-1 Vishwanath, P. R. ; Bhat, P. N. ; Ramanamurthy, P. V. ; Sreekantan, B. V. Abstract A large increase is observed in the trigger rate in the direction of Hercules X-1 in the Atmospheric Cerenkov array at Pachmarhi, India. The burst lasted from 2147 UT to 2201 UT on April 11, 1986. The accidental coincidence rate did not show any increase during the burst. Barring any electronic noise or celestial or terrestrial optical phenomenon with time structure similar to that of atmospheric Cerenkov phenomenon, the increase is ascribed to TeV gamma rays from Her X-1. The number of gamma-ray events during the burst amounted to about 54 percent of the cosmic-ray flux, resulting in a 42-sigma effect. This is the largest TeV gamma-ray signal seen from any source till now. The time-averaged flux for the burst period is 1.8 x 10 photons/sq cm per s above a threshold energy of 0.4 TeV, which results in a luminosity of 1.8 x 10 to the 37 ergs/s. The burst took place at the end of the 'high on' state in the 35-day cycle of the Her X-1 binary system indicating accretion disk as the possible production site. Publication: The Astrophysical Journal Pub Date: July 1989 DOI: 10.1086/167608 Bibcode: 1989ApJ...342..489V Keywords: Gamma Ray Bursts; Stellar Radiation; X Ray Binaries; Cerenkov Counters; Monte Carlo Method; Photon Density; Rayleigh Distribution; Astrophysics; GAMMA RAYS: BURSTS; STARS: INDIVIDUAL CONSTELLATION NAME: HERCULES X-1; X-RAYS: BINARIES full text sources ADS | data products SIMBAD (1)