The Distances of Short‐Hard Gamma‐Ray Bursts and the Soft Gamma‐Ray Repeater Connection

We present a search for nearby (D<100 Mpc) galaxies in the error boxes of sixwell-localized short-hard gamma-ray bursts (GRBs). None of the six error boxesreveals the presence of a plausible nearby host galaxy. This allows us to setlower limits on the distances and, hence, the isotropic-equivalent energy ofthese GRBs. Our lower limits are around $1 \times 10^{49}$ erg (at $2\sigma$confidence level); as a consequence, some of the short-hard GRBs we examinewould have been detected by BATSE out to distances greater than 1 Gpc andtherefore constitute a bona fide cosmological population. Our search ispartially motivated by the December 27, 2004 hypergiant flare from SGR 1806-20,and the intriguing possibility that short-hard GRBs are extragalactic events ofa similar nature. Such events would be detectable with BATSE to a distance of\~50 Mpc, and their detection rate should be comparable to the actual BATSEdetection rate of short-hard GRBs. The failure of our search, by contrast,suggests that such flares constitute less than 15% of the short-hard GRBs (<40%at 95% confidence). We discuss possible resolutions of this discrepancy.Comment: Enlarged sample of bursts; ApJ in pres