Optical observations of GRB 060218/SN 2006aj and its host galaxy

The supernova SN 2006aj associated with GRB 060218 is the second‐closest GRB‐SN observed to date (z=0.033) and is the clearest example of a SN associated with a Swift GRB with the earliest optical spectroscopy. Its optical data showed that this is the fastest evolving and among the least luminous GRB‐SNe (70% as luminous as SN1998bw). However, its expansion velocity and a comparison with other stripped‐envelope SNe suggest that SN2006aj is an intermediate object between Type Ic GRB‐SNe and those not accompained by a GRB. High‐resolution optical spectroscopy together with SDSS pre‐burst observations revealed that the host galaxy of SN2006aj is a low‐luminosity, metal‐poor star‐forming dwarf galaxy.