2006A&A...447L...5C

We present optical observations of the short/hard gamma-ray burst GRB050709, the first such event with an identified optical counterpart. The object is coincident with a weak X-ray source and is located inside a galaxy at redshift z=0.1606±0.0002. Multiband photometry allowed us to study the broad-band spectral energy distribution. Late-time monitoring places strong limits on any supernova simultaneous with the GRB. The host galaxy is not of early type. Spectra show that the dominant stellar population is relatively young (∼1Gyr), and that ongoing star formation is present at a level of 2-3(L/L_*)x(M_☉/yr). This is at least 2 orders of magnitude larger than that observed in the elliptical hosts of the short GRB050509B and GRB050724. This shows that at least some short GRBs originate in a young population. Short/hard GRB models based on the merger of a binary degenerate system are compatible with the host galaxy characteristics, although there is still the possibility of a connection between young stars and at least a fraction of such events.