Mass loss of red supergiants: a key ingredient for the final evolution of massive stars

Mass-loss rates during the red supergiant phase are very poorly constrained from an observational or theoretical point of view. However, they can be very high, and make a massive star lose a lot of mass during this phase, influencing considerably the final evolution of the star: will it end as a red supergiant? Will it evolve bluewards by removing its hydrogen-rich envelope? In this paper, we briefly summarise the effects of this mass loss and of the related uncertainties, particularly on the population of blue supergiant stars.Comment: 6 pages, 2 figures, to appear in the proceedings of the conference "The physics of evolved stars" dedicated to the memory of O. Chesneau (Nice, 2015). Will be published in EAS publications serie

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.Comment: 4 pages, 2 figures, accepted for publication in A&

Massive stars: stellar models and stellar yields, impact on Galactic Archaeology

The physics of massive stars depends (at least) on convection, mass loss by stellar winds, rotation, magnetic fields and multiplicity. We briefly discuss the impact of the first three processes on the stellar yields trying to identify some guidelines for future works.Comment: 8 pages, 6 figures, in press for the proceedings of IAU Symposium 334, Rediscovering our Galaxy, C. Chiappini, I. Minchev, E. Starkenburg, M. Valentini ed

Red supergiants and stellar evolution

We review the significant role played by red supergiants (RSGs) in stellar populations, and some challenges and questions they raise for theoretical stellar evolution. We present how metallicity and rotation modify the way stars go to the red part of the Hertzsprung- Russell diagram or come back from it, and how RSGs might keep a trace of their main-sequence evolution. We compare theoretical popu- lation ratios with observed ones.Comment: 11 pages, 5 figures, Betelgeuse workshop, November 2012, Paris. To be published in the European Astronomical Society Publications Series, editors: Pierre Kervella, Thibaut Le Bertre & Guy Perri