GRB 060505: A possible short-duration gamma-ray burst in a star-forming region at a redshift of 0.09

On 2006 May 5, a 4 s duration, low-energy, similar to 10(49) erg, gamma-ray burst ( GRB) was observed, spatially associated with a z = 0894 galaxy. Here we report the discovery of the GRB optical afterglow and observations of its environment using Gemini South, the Hubble Space Telescope ( HST), Chandra, Swift, and the Very Large Array. The optical afterglow of this GRB is spatially associated with a prominent star-forming region in the Sc-type galaxy 2dFGRS S173Z112. Its proximity to a star-forming region suggests that the progenitor delay time, from birth to explosion, is smaller than similar to 10 Myr. Our HST deep imaging rules out the presence of a supernova brighter than an absolute magnitude of about - 11 ( or - 12.6 in the case of maximal extinction) at about 2 weeks after the burst and limits the ejected mass of radioactive (56)Ni to be less than about 2 x 10(-4) M(circle dot) ( assuming no extinction). Although it was suggested that GRB 060505 may belong to a new class of long-duration GRBs with no supernova, we argue that the simplest interpretation is that the physical mechanism responsible for this burst is the same as that for short-duration GRBs.