A binary progenitor for the Type Ib Supernova iPTF13bvn

The recent detection in archival HST images of an object at the the location of supernova (SN) iPTF13bvn may represent the first direct evidence of the progenitor of a Type Ib SN. The object's photometry was found to be compatible with a Wolf-Rayet pre-SN star mass of ~ 11 M _⊙. However, based on hydrodynamical models we show that the progenitor had a pre-SN mass of ~ 3.5 M _⊙ and that it could not be larger than ~ 8 M _⊙. We propose an interacting binary system as the SN progenitor and perform evolutionary calculations that are able to self-consistently explain the light-curve shape, the absence of hydrogen, and the pre-SN photometry. Our models also predict that the remaining companion is a luminous O-type star of significantly lower flux in the optical than the pre-SN object. A future detection of such star may be possible and would provide the first robust progenitor identification for a Type-Ib SN.