paper

Short GRBs: opening angles, local neutron star merger rate and off-axis events for GRB/GW association

arXiv:1708.07008 · doi:10.3847/1538-4357/aab76d

Abstract

The jet breaks in the afterglow lightcurves of short gamma-ray bursts (SGRBs), rarely detected so far, are crucial for estimating the half-opening angles of the ejecta () and hence the neutron star merger rate. In this work we report the detection of jet decline behaviors in GRB 150424A and GRB 160821B and find rad. Together with five events reported before 2015 and other three "identified" recently (GRB 050709, GRB 060614 and GRB 140903A), we have a sample consisting of nine SGRBs and one long-short GRB with reasonably estimated . In particular, three {\it Swift} bursts in the sample have redshifts , with which we estimate the local neutron star merger rate density {to be or if the narrowly-beamed GRB 061201 is excluded}. Inspired by the typical rad found currently, we further investigate whether the off-beam GRBs (in the uniform jet model) or the off-axis events (in the structured jet model) can significantly enhance the GRB/GW association or not. For the former the enhancement is at most moderate, while for the latter the enhancement can be much greater and a high GRB/GW association probability of is possible. We also show that the data of GRB 160821B may contain a macronova/kilonova emission component with a temperature of K at days after the burst and more data are needed to ultimately clarify.

14 pages, 8 figures, accepted for publication in ApJ

References in corpus (30)

Cited by in corpus (77)