An off-line scan of the BATSE daily records and a large uniform sample of gamma-ray bursts

During a scan of the archival BATSE daily records covering the entire 9.1 yr (TJD 8369-11690) of the BATSE operation, 3906 gamma-ray bursts (GRBs) have been detected. 2068 of these GRBs are previously known BATSE triggers, while 1838 of them are new nontriggered bursts. It is important that all events were detected in the same type of data and were processed with the same procedure. Therefore these 3906 GRBs constitute a uniform sample. We have created a publicly available electronic data base(4) containing this sample. We describe the procedures of the data reduction, the selection of the GRB candidates, and the statistical tests for possible non-GRB contaminations. We also describe a novel test burst method used to measure the scan efficiency and the information obtained using the test bursts. Our scan decreases the BATSE detection threshold to similar to0.1 photon s(-1) cm(-2). As a first result, we show that the differential log N- log P distribution corrected for the detection efficiency extends to low brightnesses without any indication of a turnover. Any reasonable extrapolation of the new log N- log P to lower brightnesses imply a rate of several thousands of GRBs in the universe per year.