Research
Grids of stellar models
Since 1992, our group has provided extended grids of stellar models for the astronomical community. First the Schaller et al. series of 7 papers on non-rotating models (see ADS), then the series of 13 papers on stellar evolution with rotation (see ADS), and finally the series of 4 papers on rotation and magnetic fields (see ADS).
In the last series, the prescriptions used to treat the effects of rotation were not identical throughout the whole set of models. We thus decided to start the computation of a new set of grids. We will provide two different grids:
a large grid with masses ranging from 0.8 to 120 Msol, different metallicities (Zsol, ZLMC, ZSMC, ZI Zwi 18, Z=10-5, ...) and for each M and Z two models: a non-rotating one and one rotating at v/vcrit=0.40.
a smaller mass range (from 1.7 to 15 Msol) and fewer metallicities (Zsol, ZLMC, ZSMC) but a denser coverage in rotation rates (Ω/Ωcrit= 0, 0.1, 0.3, 0.5, 0.6, 0.7, 0.8, 0.9, and 0.95).
The first paper of the large grid (Zsol) has been published in January 2012, and the corresponding models can be found through our database page or at the CDS database.
The conditions preveiling in the Universe during the first minutes after the Big Bang have allowed the nucleosynthesis of the very light elements as hydrogen, helium, lithium, and traces of carbon or nitrogen. The very first stars to be formed in the Universe a few hundreds of millions years later come from a medium totally deficient in metals. These stars, probably extremely massive, have started to synthetize the heavy elements up to iron during their very short life. Their explosive death allows the enrichment of the primordial medium and the formation of less massive stars, which we may still observe nowadays (as HE0107-5240 or HE1327-2326). These stars exhibit very peculiar chemical abundances at their surface and one may think that it is a chemical signature of primordial stars.
My PhD work consisted in modeling the evolutionary tracks of primordial stars in order to explore the effects of non solid rotation on these objects. Rotation has two major effects: first the extremely metal-poor stars reach easily the break-up limit and may lose a significant amount of mass because of centrifugal force. Then differential rotation induce a strong mixing inside the star. This mixing favours the enrichment of the surface in heavy elements, leading to non negligible stellar winds, and modifies the chemical abundances profiles inside the star. All this will have a very important effect on the enrichment of the surrounding medium, and thus on the evolution of the primordial Universe.
