Comparison of the gamma-ray burst sensitivity of different detectors

Gamma-ray burst detectors are sensitive at different energies, complicating the comparison of the burst populations that they detect. Instrument teams often report their detector sensitivities in their instruments' energy band. I propose that sensitivities be reported as the threshold peak photon flux F-T over the 1-1000 keV energy band for a specific spectral shape. The primary spectral parameter is E-p, the energy of the maximum E-2 N(E) proportional to nuf(nu). Thus, F-T versus E-p is a useful description of a detector's sensitivity. I find that Swift will be marginally more sensitive than BATSE for E-p > 100 keV but significantly more sensitive for E-p < 100 keV. Because of its low energy sensitivity, the FREGATE on HETE-2 is surprisingly sensitive below E-p = 100 keV. Both the WFC on BeppoSAX and the WXM on HETE-2 are/were sensitive for low E-p. As expected, the GBM on GLAST will be less sensitive than BATSE, while EXIST will be significantly more sensitive than Swift. The BeppoSAX GRBM was less sensitive that the WFC, particularly at low E-p.