A Search for Nontriggered Gamma‐Ray Bursts in the BATSE Database

We describe a search of archival data from the Burst and Transient Source Experiment (BATSE). The purpose of the search is to nd astronomically interesting transients that did not activate the burstdetection (or "" trigger ) system on board the spacecraft. Our search is sensitive to events with peak uxes (on the 1.024 s timescale) that are lower by a factor of D2 than can be detected with the on-board burst trigger. In a search of 345 days of archival data, we detected 91 events in the 50300 keV range that resemble classical gamma-ray bursts but that did not activate the on-board burst trigger. We also detected 110 low-energy (2550 keV) events of unknown origin that may include activity from soft gamma repeater (SGR) 1806[20 and bursts and ares from X-ray binaries. This paper gives the occurrence times, estimated source directions, durations, peak uxes, and uences for the 91 gamma-ray burst candidates. The direction and intensity distributions of these bursts imply that the biases inherent in the on-board trigger mechanism have not signicantly a ected the completeness of the published BATSE gamma-ray burst catalogs.