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.

We have re-evaluated empirical expressions for the abundance determination of N, O, Ne, S, Cl, Ar and Fe taking into account the latest atomic data and constructing an appropriate grid of photoionization models with state-of-the art model atmospheres. Using these expressions we have derived heavy element abundances in the ∼310 emission-line galaxies from the Data Release 3 of the Sloan Digital Sky Survey (SDSS) with an observed Hβ flux F(Hβ) > 10 −14 erg s −1 cm −2 and for which the [O iii] λ4363 emission line was detected at least at a 2σ level, allowing abundance determination by direct methods. The oxygen abundance 12 + log O/H of the SDSS galaxies lies in the range from ∼7.1 (Z /30) to ∼8.5 (0.7 Z ). The SDSS sample is merged with a sample of 109 blue compact dwarf (BCD) galaxies with high quality spectra, which contains extremely low-metallicity objects. We use the merged sample to study the abundance patterns of low-metallicity emission-line galaxies. We find that extremely metal-poor galaxies (12 + log O/H < 7.6, i.e. Z < Z /12) are rare in the SDSS sample. The α element-to-oxygen abundance ratios do not show any significant trends with oxygen abundance, in agreement with previous studies, except for a slight increase of Ne/O with increasing metallicity, which we interpret as due to a moderate depletion of O onto grains in the most metal-rich galaxies. The Fe/O abundance ratio is smaller than the solar value, by up to 1 dex at the high metallicity end. We also find that Fe/O increases with decreasing Hβ equivalent width EW(Hβ). We interpret this as a sign of strong depletion onto dust grains, and gradual destruction of those grains on a time scale of a few Myr. All the galaxies are found to have log N/O > -1.6, implying that they have a different nature than the subsample of high-redshift damped Lyα systems with log N/O of ∼-2.3 and that their ages are larger than 100-300 Myr. We confirm the apparent increase in N/O with decreasing EW(Hβ), already shown in previous studies, and explain it as the signature of gradual nitrogen ejection by massive stars from the most recent starburst.

Aims. We propose the Wind of Fast Rotating Massive Stars scenario to explain the origin of the abundance anomalies observed in globular clusters. Methods. We compute and present models of fast rotating stars with initial masses between 20 and 120 M for an initial metallicity Z = 0.0005 ([Fe/H] −1.5). We discuss the nucleosynthesis in the H-burning core of these objects and present the chemical composition of their ejecta. We consider the impact of uncertainties in the relevant nuclear reaction rates. Results. Fast rotating stars reach critical velocity at the beginning of their evolution and remain near the critical limit during the rest of the main sequence and part of the He-burning phase. As a consequence they lose large amounts of material through a mechanical wind which probably leads to the formation of a slow outflowing disk. The material in this slow wind is enriched in H-burning products and presents abundance patterns similar to the chemical anomalies observed in globular cluster stars. In particular, the C, N, O, Na and Li variations are well reproduced by our model. However the rate of the 24 Mg(p, γ) has to be increased by a factor 1000 around 50 × 10 6 K in order to reproduce the amplitude of the observed Mg-Al anticorrelation. We discuss how the long-lived low-mass stars currently observed in globular clusters could have formed out of the slow wind material ejected by massive stars.

▪ Abstract  In this article we first review the main physical effects to be considered in the building of evolutionary models of rotating stars on the Upper Main-Sequence (MS). The internal rotation law evolves as a result of contraction and expansion, meridional circulation, diffusion processes, and mass loss. In turn, differential rotation and mixing exert a feedback on circulation and diffusion, so that a consistent treatment is necessary. We review recent results on the evolution of internal rotation and the surface rotational velocities for stars on the Upper MS, for red giants, supergiants, and W-R stars. A fast rotation enhances the mass loss by stellar winds and, conversely, high mass loss removes a lot of angular momentum. The problem of the breakup or Ω-limit is critically examined in connection with the origin of Be and LBV stars. The effects of rotation on the tracks in the HR diagram, the lifetimes, the isochrones, the blue-to-red supergiant ratios, the formation of Wolf-Rayet stars, and the chemical abundances in massive stars as well as in red giants and AGB stars are reviewed in relation to recent observations for stars in the Galaxy and Magellanic Clouds. The effects of rotation on the final stages and on the chemical yields are examined, along with the constraints placed by the periods of pulsars. On the whole, this review points out that stellar evolution is not only a function of mass M and metallicity Z, but of angular velocity Ω as well.

Abstract.We examine the properties of Wolf-Rayet (WR) stars predicted by models of rotating stars taking account of the new mass loss rates for O-type stars and WR stars (Vink et al. 2000(Vink et al. , 2001Nugis & Lamers 2000) and of the wind anisotropies induced by rotation. We find that the rotation velocities v of WR stars are modest, i.e. about 50 km s −1 , not very dependent on the initial v and masses. For the most massive stars, the evolution of v is very strongly influenced by the values of the mass loss rates; below ∼12 M the evolution of rotation during the MS phase and later phases is dominated by the internal coupling. Massive stars with extreme rotation may skip the LBV phase. Models having a typical v for the O-type stars have WR lifetimes on the average two times longer than for non-rotating models. The increase of the WR lifetimes is mainly due to that of the H-rich eWNL phase. Rotation allows a transition WN/WC phase to be present for initial masses lower than 60 M . The durations of the other WR subphases are less affected by rotation. The mass threshold for forming WR stars is lowered from 37 to 22 M for typical rotation. The comparisons of the predicted number ratios WR/O, WN/WC and of the number of transition WN/WC stars show very good agreement with models with rotation, while this is not the case for models with the present-day mass loss rates and no rotation. As to the chemical abundances in WR stars, rotation brings only very small changes for WN stars, since they have equilibrium CNO values. However, WC stars with rotation have on average lower C/He and O/He ratios. The luminosity distribution of WC stars is also influenced by rotation.