Progenitors of supernova Ibc: a single Wolf-Rayet star as the possible
  progenitor of the SN Ib iPTF13bvn
  Core-collapse supernova (SN) explosions mark the end of the tumultuous life
of massive stars. Determining the nature of their progenitors is a crucial step
towards understanding the properties of SNe. Until recently, no progenitor has
been directly detected for SN of type Ibc, which are believed to come from
massive stars that lose their hydrogen envelope through stellar winds and from
binary systems where the companion has stripped the H envelope from the
primary. Here we analyze recently reported observations of iPTF13bvn, which
could possibly be the first detection of a SN Ib progenitor based on
pre-explosion images. Very interestingly, the recently published Geneva models
of single stars can reproduce the observed photometry of the progenitor
candidate and its mass-loss rate, confirming a recently proposed scenario. We
find that a single WR star with initial mass in the range 31-35 Msun fits the
observed photometry of the progenitor of iPTF13bvn. The progenitor likely has a
luminosity of log (L/Lsun)~5.55, surface temperature ~45000 K, and mass of
~10.9 Msun at the time of explosion. Our non-rotating 32 Msun model
overestimates the derived radius of the progenitor, although this could likely
be reconciled with a fine-tuned model of a more massive (between 40 and 50
Msun), hotter, and luminous progenitor. Our models indicate a very uncertain
ejecta mass of ~8 Msun, which is higher than the average of the SN Ib ejecta
mass that is derived from the lightcurve (2-4 Msun). This possibly high ejecta
mass could produce detectable effects in the iPTF13bvn lightcurve and spectrum.
If the candidate is indeed confirmed to be the progenitor, our results suggest
that stars with relatively high initial masses (>30 Msun) can produce visible
SN explosions at their deaths and do not collapse directly to a black hole.
