Program: GN-2012B-Q-97

In recent years we have at last begun to make progress in understanding the population of short gamma-ray bursts (short-GRBs), in particular because afterglows are now detected for a large fraction of these enigmatic sources. In contrast with long bursts, for a significant fraction of short-GRBs no host galaxy is found at the afterglow position. This may be expected in a scenario where short-GRBs are formed through a compact object binary merger (e.g. a neutron star binary, or neutron star - black hole binary), which may be kicked out of its host galaxy through supernova kicks and mass loss during its lifetime. We aim to test this scenario by obtaining redshifts of galaxies nearby (within several tens of arc seconds) the afterglow positions of "host-less" S-GRBs. In particular, we target the galaxies with a low probability of being found very close to a GRB position by chance: our analysis has shown that host-less short-GRBs have a much higher likelihood of association with proximate galaxies than a sample of random locations. Finding a most probable redshift for a selection of host-less short-GRBs will allow us to test formation scenarios of short-GRBs in a more complete way.