Yellow supergiants as supernova progenitors: an indication of strong   mass loss for red supergiants?
  The increasing observed number of supernova events allows for finding ever more frequently the progenitor star in archive images. In a few cases, the progenitor star is a yellow supergiant star. The estimated position in the Hertzsprung-Russell diagram of these stars is not compatible with the theoretical tracks of classical single star models. According to several authors, the mass-loss rates during the red supergiant phase could be underestimated. We study the impact of an increase of these mass-loss rates on the position of 12 to 15 M\odot stars at the end of their nuclear life, in order to reconcile the theoretical tracks with the observed yellow supergiant progenitors. We perform calculations of 12 to 15 M\odot rotating stellar models using the Geneva stellar evolution code. To account for the uncertainties in the mass-loss rates during the RSG phase, we increase the mass-loss rate of the star (between 3 and 10 times the standard one) during that phase and compare the evolution of stars undergoing such high mass-loss rates with models computed with the standard mass-loss prescription. We show that the final position of the models in the Hertzsprung-Russell diagram depends on the mass loss they undergo during the red supergiant phase. With an increased mass-loss rate, we find that some models end their nuclear life at positions that are compatible with the observed position of several supernova progenitors. We conclude that an increased mass-loss rate (whom physical mechanism still need to be clarified) allows single star models to reproduce simultaneously the estimated position in the HRD of the YSG SN progenitors, as well as the SN type. 
Cyril Georgy
astro-ph.SR