Probing the low-luminosity GRB population with new generation satellite detectors

摘要

We compare the detection rates and redshift distributions of low-luminosity(LL) GRBs localized by Swift with those expected to be observed by the newgeneration satellite detectors on GLAST (now Fermi) and, in future, EXIST.Although the GLAST burst telescope will be less sensitive than Swift's in the15--150 keV band, its large field-of-view implies that it will double Swift'sdetection rate of LL bursts. We show that Swift, GLAST and EXIST should detectabout 1, 2 & 30 LL GRBs, respectively, over a 5-year operational period. Theburst telescope on EXIST should detect LL GRBs at a rate of more than an orderof magnitude greater than that of Swift's BAT. We show that the detectionhorizon for LL GRBs will be extended from $z \simeq 0.4$ for Swift to $z \simeq1.1$ in the EXIST era. Also, the contribution of LL bursts to the observed GRBredshift distribution will contribute to an identifiable feature in thedistribution at $z \simeq 1$.