BATSE Gamma‐Ray Burst Line Search. V. Probability of Detecting a Line in a Burst

The physical importance of the apparent discrepancy between the detections bypre-BATSE missions of absorption lines in gamma-ray burst spectra and theabsence of a BATSE line detection necessitates a statistical analysis of thisdiscrepancy. This analysis requires a calculation of the probability that aline, if present, will be detected in a given burst. However, the connectionbetween the detectability of a line in a spectrum and in a burst requires amodel for the occurrence of a line within a burst. We have developed thenecessary weighting for the line detection probability for each spectrumspanning the burst. The resulting calculations require a description of eachspectrum in the BATSE database. With these tools we identify the bursts inwhich lines are most likely to be detected. Also, by assuming a small frequencywith which lines occur, we calculate the approximate number of BATSE bursts inwhich lines of various types could be detected. Lines similar to the Gingadetections can be detected in relatively few BATSE bursts; for example, in only~20 bursts are lines similar to the GB 880205 pair of lines detectable. Gingareported lines at ~20 and ~40 keV whereas the low energy cutoff of the BATSEspectra is typically above 20 keV; hence BATSE's sensitivity to lines is lessthan that of Ginga below 40 keV, and greater above. Therefore the probabilitythat the GB 880205 lines would be detected in a Ginga burst rather than a BATSEburst is ~0.2. Finally, we adopted a more appropriate test of the significanceof a line feature.Comment: 20 pages, AASTeX 4.0, 5 figures, Ap.J. in pres