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

We describe a search of archival data from the Burst and Transient SourceExperiment (BATSE). The purpose of the search is to find astronomicallyinteresting transients that did not activate the burst detection (or``trigger'') system onboard the spacecraft. Our search is sensitive to eventswith peak fluxes (on the 1.024 s time scale) that are lower by a factor of 2than can be detected with the onboard burst trigger. In a search of 345 days ofarchival data, we detected 91 events in the 50--300 keV range that resembleclassical gamma ray bursts but that did not activate the onboard burst trigger.We also detected 110 low-energy (25--50 keV) events of unknown origins whichmay include activity from SGR 1806-20 and bursts and flares from X-raybinaries. This paper gives the occurrence times, estimated source directions,durations, peak fluxes, and fluences for the 91 gamma ray burst candidates. Thedirection and intensity distributions of these bursts imply that the biasesinherent in the onboard trigger mechanism have not significantly affected thecompleteness of the published BATSE gamma ray burst catalogs.