Comparison of the Gamma-Ray Burst Sensitivity of Different Detectors

Abstract

Gamma-ray burst detectors are sensitive at different energies, complicating the comparison of the burst populations that they detect. The 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 propto nu f_nu. Thus F_T vs. 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.