AAS Meeting #193 - Austin, Texas, January 1999
Session 79. Gamma-Ray Bursts I
Oral, Friday, January 8, 1999, 10:00-11:30am, Ballroom A

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[79.07D] The Non-triggered Supplement to the BATSE Gamma-ray Burst Catalogs

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

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