Formation Scenario of the Progenitor of iPTF13bvn Revisited
  The formation scenario of the progenitor of iPTF13bvn has been revisited. iPTF13bvn is unique in the sense that a corresponding pre-supernova image has been identified. This has enabled us to strongly constrain the nature of its progenitor. From the pre-supernova image, light curve and the latest observations, it is currently widely accepted that the progenitor of iPTF13bvn was in a binary system. The fast decline in the light curve suggests a progenitor mass of $\sim3.5M_\odot$, and the upper limit on the remaining companion is $\sim20M_\odot$. Recent works suggest that binary evolution models involving common envelope episodes can satisfy all the observational constraints. We have examined the common envelope scenario based on latest knowledges on common envelope evolution. We have found that the common envelope scenario for the progenitor of iPTF13bvn seems not to be suitable since it can not explain the pre-supernova radius. We also propose an alternative model with a black hole companion. Stellar evolution calculations with a large black hole companion were carried out and succeeded in satisfying all observational constraints. However, more studies should be carried out to explain the origin of the large black hole companion. 
Ryosuke Hirai
astro-ph.HE astro-ph.SR