Grids of stellar models with rotation

Abstract

Aims. Many topical astrophysical research areas, such as the properties of planet host stars, the nature of the progenitors of different types of supernovae and gamma ray bursts, and the evolution of galaxies, require complete and homogeneous sets of stellar models at different metallicities in order to be studied during the whole of cosmic history. We present here a first set of models for solar metallicity, where the effects of rotation are accounted for in a homogeneous way. Methods. We computed a grid of 48 different stellar evolutionary tracks, both rotating and non-rotating, at Z = 0.014, spanning a wide mass range from 0.8 to 120 M . For each of the stellar masses considered, electronic tables provide data for 400 stages along the evolutionary track and at each stage, a set of 43 physical data are given. These grids thus provide an extensive and detailed data basis for comparisons with the observations. The rotating models start on the zero-age main sequence (ZAMS) with a rotation rate υ ini /υ crit = 0.4. The evolution is computed until the end of the central carbon-burning phase, the early asymptotic giant branch (AGB) phase, or the core helium-flash for, respectively, the massive, intermediate, and both low and very low mass stars. The initial abundances are those deduced by Asplund and collaborators, which best fit the observed abundances of massive stars in the solar neighbourhood. We update both the opacities and nuclear reaction rates, and introduce new prescriptions for the mass-loss rates as stars approach the Eddington and/or the critical velocity. We account for both atomic diffusion and magnetic braking in our low-mass star models.Results. The present rotating models provide a good description of the average evolution of non-interacting stars. In particular, they reproduce the observed main-sequence width, the positions of the red giant and supergiant stars in the Hertzsprung-Russell (HR) diagram, the observed surface compositions and rotational velocities. Very interestingly, the enhancement of the mass loss during the red-supergiant stage, when the luminosity becomes supra-Eddington in some outer layers, help models above 15−20 M to lose a significant part of their hydrogen envelope and evolve back into the blue part of the HR diagram. This result has interesting consequences for the blue to red supergiant ratio, the minimum mass for stars to become Wolf-Rayet stars, and the maximum initial mass of stars that explode as type II−P supernovae.

A young cluster with an extended main-sequence turnoff: confirmation of a prediction of the stellar rotation scenario

“…While initial works cast doubt on this mechanism (Girardi et al 2011), stellar models that include rotation have been developed in recent years (e.g., Ekström et al 2012, Georgy et al 2013) which can be directly compared against observations. Such comparisons have been done for intermediate age clusters (Brandt & Huang 2015a,b) and it seems that for realistic rotational distributions (like those observed in open clusters -Huang et al 2010) extended MSTOs are expected to be a common feature.…”

Evolution and Nucleosynthesis of Massive Stars

“…Also the minimum mass of single star entering a Wolf-Rayet stage is decreased by rotation. Many grids of rotating stellar models have appeared in the last decade [4,11,16,20,51]. Although these grids are all presented under the generic name of rotating stellar models, they are computed sometimes with very different physics.…”

“…The general theoretical framework of these models has been given by [59]. These models have the following characteristics [11,16,20]:…”

“…The upper labels indicate the type of the core collapse progenitors. Models of [16] and of [20] have been used.…”

Massive stars, successes and challenges

“…the turbulence along an isobar. In the last Geneva grid at solar metallicity (Ekström et al 2012), the choice of these two quantities was mainly driven by requiring that stars with initial masses between 9 and 15 M at solar metallicity, presenting a surface velocity during the Main-Sequence phase compatible with the observed averaged velocities present nitrogen surface enrichments in agreement with the mean observed values. Note that this way of doing is shared by other groups (Brott et al 2001, Chieffi & Limongi 2013 and thus the stellar models will predict similar values in this mass and velocity range at the solar metallicity.…”