High Energy Transient Events From Cygnus X-1: Evidence for a Source of Galactic Gamma-Ray Bursts
Abstract
We investigate the possibility that at least some gamma-ray bursts (GRBs) listed in the Compton Gamma-ray Observatory Burst and Transient Source Experiment (BATSE) 3B catalog originate from known galactic X-ray sources. We find that there is a slight, but not statistically significant, excess of BATSE GRBs in the direction of Scorpius X-1. This is consistent with there being at most only a few triggered GRBs originating from Sco X-1. We present evidence that three of these bursts might be high energy transient events associated with accretion in Sco X-1. Due to the lack of an excess of GRBs from the galactic center and galactic plane we conclude that galactic X-ray binaries cannot account for a significant number of GRBs. However, many BATSE bursts originate from the black hole candidate Cygnus X- 1. This is supported by the fact that the surface density on the sky of bursts in the direction of Cyg X- 1 is more than a factor of 2 greater than the average for the rest of the sky. We show that the process used to remove these bursts from the BATSE catalog has resulted in an anomalous <V/Vmax> (a measure of the average burst intensity) for the region of the sky near Cyg X- 1. We interpret this result as being evidence that some of the strong bursts remaining in the BATSE 3B catalog are actually Cyg X-2 accretion events and some of the weak bursts attributed to Cyg X-1 and removed from the BATSE 3B catalog are actually "classical" gamma-ray bursts. Since these Cyg X-1 accretion related bursts are apparently indistinguishable from the other GRBs, we suggest that accretion onto cosmological black holes may be responsible for the general population of GRBs.
- Publication:
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The Astronomical Journal
- Pub Date:
- July 1997
- DOI:
- Bibcode:
- 1997AJ....114..238M
- Keywords:
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- X-RAYS: BURSTS