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Session 43 - Source Surveys.
Display session, Wednesday, June 11
South Main Hall,

[43.10] A Search for Faint (Non-triggered) Gamma Ray Bursts in the BATSE Data Base

J. M. Kommers, W. H. G. Lewin (MIT), C. Kouveliotou (USRA), J. van Paradijs (UAH and U. Amsterdam), G. N. Pendleton (U. Alabama, Huntsville), C. A. Meegan, G. J. Fishman (NASA/MSFC)

We describe a search of archival data from the Burst and Transient Source Experiment (BATSE) onboard the Compton Gamma Ray Observatory. The purpose of the search is to find astronomically interesting transients that did not activate the burst detection (or ``trigger'') system onboard the spacecraft but that nevertheless left a statistically significant signal in the continuous data. Our search is sensitive to gamma ray bursts with peak fluxes (on the 1.024 s time scale) that are lower by a factor of \sim 2 than can be detected with the onboard burst trigger. In a search of 345 days of archival data, we detected 91 events in the 50--300 keV range that resemble classical gamma ray bursts but that did not activate the onboard burst trigger. We also detected 110 low-energy (25--50 keV) events of unknown origin which may include activity from SGR 1806-20 and bursts and flares from X-ray binaries. The direction and intensity distributions of the 91 gamma ray burst candidates imply that the biases inherent in the onboard trigger mechanism have not significantly undermined the completeness of the published BATSE gamma ray burst catalogs.

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