Yellow supergiants as supernova progenitors: an indication of strong mass loss for red supergiants?

Centre de Recherche Astrophysique de Lyon, École Normale Supérieure de Lyon, 46 allée d’Italie, 69384 Lyon Cedex 07, France
e-mail: cyril.georgy@unige.ch

Received: 1 November 2011
Accepted: 8 December 2011

Abstract

Context. The increasing number of observed supernova events allows for finding the progenitor star even more frequently 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.

Aims. According to several authors, the mass-loss rates during the red supergiant phase could be underestimated. We study the impact of an increase in these mass-loss rates on the position of 12 to 15 M_⊙ stars at the end of their nuclear lives, in order to reconcile the theoretical tracks with the observed yellow supergiant progenitors.

Methods. We have performed calculations of 12 to 15 M_⊙ rotating stellar models using the Geneva stellar evolution code. To account for the uncertainties in the mass-loss rates during the RSG phase, we increased the mass-loss rate of the star (between 3 and 10 times the standard one) during that phase and compared the evolution of stars undergoing such high mass-loss rates with models computed with the standard mass-loss prescription.

Results. 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 (whose physical mechanism still needs to be clarified) allows single-star models to simultaneously reproduce the estimated position in the HRD of the YSG SN progenitors, as well as the SN type.