The sensitivity of the BATSE spectroscopy detectors to cyclotron lines in gamma-ray bursts

As of October 16, 1992, we have examined 72 gamma-ray bursts (GRBs) using the BATSE Spectroscopy Detectors (SDs) and have found no convincing evidence for cyclotron absorption lines. This contrasts with the results of Ginga, which found lines in 3 out of 23 examined GRBs. 1,2,3 These results are not necessarily in conflict, as many of the 72 SD bursts were so weak that lines with the relative strengths measured by Ginga would not have been detectable. A comparison of these results therefore requires a determination of the sensitivity of each instrument to cyclotron lines in the observed bursts. Simulations based on the cyclotron line spectra found by Ginga were used to estimate our sensitivity. We Eind that 12-18 bursts (depending on the assumed duration of the lines) were bright enough that typical Ginga second harmonic cyclotron lines would have been detectable at the P\u3c10 -4 (3.8σ) level in the most favorable detector. Comparison to a similar analysis by Fenimore et al. 4 shows that the Ginga and SD results are not significantly in conflict