Wednesday

Following the faint gamma-ray burst, GRB 170817A, coincident with a gravitational wave-detected binary neutron star merger at d∼40 Mpc, we consider the constraints on a local population of faint short duration GRBs (defined here broadly as T904 s). We review proposed low-redshift short-GRBs and consider statistical limits on a d⪅200 Mpc population using Swift/Burst Alert Telescope (BAT), Fermi/Gamma-ray Burst Monitor (GBM), and Compton Gamma-Ray Observatory (CGRO) Burst and Transient Source Experiment (BATSE) GRBs. Swift/BAT short-GRBs give an upper limit for the all-sky rate of 4 y−1 at d200 Mpc, corresponding to 5% of SGRBs. Cross-correlation of selected CGRO/BATSE and Fermi/GBM GRBs with d100 Mpc galaxy positions returns a weaker constraint of ⪅12 y−1. A separate search for correlations due to SGR giant flares in nearby (d11 Mpc) galaxies finds an upper limit of 3 y−1. Our analysis suggests that GRB 170817A-like events are likely to be rare in existing SGRB catalogues. The best candidate for an analogue remains GRB 050906, where the Swift/BAT location was consistent with the galaxy IC0327 at d≈132 Mpc. If binary neutron star merger rates are at the high end of current estimates, then our results imply that at most a few percent will be accompanied by detectable gamma-ray flashes in the forthcoming LIGO/Virgo science runs.