Evolution of rotating massive stars with new hydrodynamic wind models

Abstract

Context. Mass loss due to radiatively line-driven winds is central to our understanding of the evolution of massive stars in both single and multiple systems. This mass loss plays a key role in modulating the stellar evolution at different metallicities, particularly in the case of massive stars with M* ≥ 25 M⊙. Aims. We extend the evolution models introduced in Paper I, where the mass-loss recipe is based on the simultaneous calculation of the wind hydrodynamics and the line acceleration, by incorporating the effects of stellar rotation. Methods. As in Paper I, we introduce a grid of self-consistent line-force parameters (k, α, δ) for a set of standard evolutionary tracks using GENEC. Based on this grid, we analysed the effects of stellar rotation, CNO abundances, and He/H ratio on the wind solutions to derive additional terms for the recipe with which we predict the self-consistent mass-loss rate, Ṁsc. With this, we generated a new set of evolutionary tracks with rotation for MZAMS = 25, 40, 70, and 120 M⊙, and for metallicities Z = 0.014 (Galactic) and 0.006 (Large Magellanic Cloud). Results. In addition to the expected correction factor due to rotation, the mass-loss rate decreases when the surface becomes more helium rich, especially in the later moments of the main-sequence phase. The self-consistent approach gives lower mass-loss rates than the standard values adopted in previous GENEC evolution models. This decrease strongly affects the tracks of the most massive models. Weaker winds allow the star to retain more mass, but also more angular momentum. As a consequence, weaker wind models rotate faster and show a less efficient mixing in their inner stellar structure at a given age. Conclusions. The self-consistent tracks predict an evolution of the rotational velocities through the main sequence that closely agrees with the range of v sin i values found by recent surveys of Galactic O-type stars. As subsequent implications, the weaker winds from self-consistent models also suggest a reduction of the contribution of the isotope 26Al to the interstellar medium due to stellar winds of massive stars during the MS phase. Moreover, the higher luminosities found for the self-consistent evolutionary models suggest that some populations of massive stars might be less massive than previously thought, as in the case of Ofpe stars at the Galactic centre. Therefore, this study opens a wide range of consequences for further research based on the evolution of massive stars.