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J. M. Kommers, W. H. G. Lewin (MIT), C. Kouveliotou (USRA), J. van Paradijs (U. Amsterdam, UAH), G. N. Pendleton (UAH), C. A. Meegan, G. J. Fishman (NASA/MSFC)
The Burst and Transient Source Experiment (BATSE) onboard the Compton Gamma Ray Observatory detects gamma-ray bursts (GRBs) and other astronomical transients using a real-time burst detection (or ``trigger'') system running onboard the spacecraft. I describe a search of 6 years of archival BATSE data for GRBs and other transients that were not detected by the onboard system. The result is a catalog of ``non-triggered'' GRBs. This catalog increases the number of GRBs detected with BATSE by 48% during the time period of the search.
The intensity distribution of the GRBs detected with our search (both triggered and non-triggered) reaches peak fluxes that are a factor of ~2 lower than could be studied previously. The mean value of the V/Vmax statistic for these bursts is 0.177 ±0.006. This is the lowest value so far obtained for a global sample of GRBs. The differential peak flux distribution is consistent with cosmological models in which the co-moving gamma-ray burst rate approximately traces the star formation history of the Universe. These results suggest that more sensitive detectors are likely to discover relatively few ``classical'' GRBs fainter than the BATSE detection threshold.
The author(s) of this abstract have provided an email address for comments about the abstract: kommers@space.mit.edu