Evolution of massive stars with new hydrodynamic wind models

Abstract

Context. Mass-loss by radiatively line-driven winds is central to our understanding of massive star evolution either single or in multiple systems. It for instance plays a key role in making massive star evolution different at different metallicities, specially in the case of very massive stars (M * ≥ 25M ).Aims. Here we present evolutionary models for a set of massive stars, introducing a new prescription for the mass-loss rate obtained from hydrodynamical calculations in which the wind velocity profile, (r), and the line-acceleration, g line , are obtained in a self consistently way. These new prescriptions cover the most part of the Main-Sequence phase of O-type stars. Methods. We perform a grid of self-consistent mass-loss rates Ṁsc , for a set of standard evolutionary tracks (i.e., using the old prescription for mass-loss rate) under different values for initial mass and metallicity. Based in this grid, we elaborate a statistical analysis to create a new simple formula predicting the values of Ṁsc just from the stellar parameters, without assuming any extra condition for the wind description. Therefore, replacing mass-loss rates at the Main Sequence stage from the standard Vink's formula by our new recipe, we generate a new set of evolutionary tracks for M ZAMS = 25, 40, 70 and 120 M and metallicities Z = 0.014 (Galactic), Z = 0.006 (LMC), and Z = 0.002 (SMC). Results. Our new derived formula for mass-loss rate predicts a dependence Ṁ ∝ Z a , where a is not longer constant but dependent on the stellar mass: ranging from a ∼ 0.53 when M * ∼ 120 M , to a ∼ 1.02 when M * ∼ 25 M . We found important differences between standard and our new self-consistent tracks. Models adopting the new recipe for Ṁ (which starts being around ∼ 3 times weaker than mass-loss rate from the old formulation) retain more mass during their evolution, which is expressed in larger radii and consequently more luminous tracks over the Hertzsprung-Russell diagram. These differences are more prominent for the cases of M ZAMS = 70 and 120 M at solar metallicity, where we found self-consistent tracks are ∼ 0.1 dex brighter and keep extra mass up to 20 M , compared with the classical models using the previous formulation for mass-loss rate. Later increments in the mass-loss rate for tracks when self-consistency is not longer used, attributed to the LBV stage, produce different final stellar radii and masses before the end of H-burning stage, which are analysed case to case. Moreover, we observed remarkable differences for the evolution of the radionuclide isotope 26 Al in the core and the surface of the star. Since Ṁsc are weaker than the commonly adopted values for evolutionary tracks, self-consistent tracks predict a later modification in the abundance number of 26 Al in the stellar winds. This new behaviour could provide useful information about the real contribution of this isotope from massive stars to the Galactic interstellar medium.

New mass-loss rates of B supergiants from global wind models

“…The present paper provides further support for the downward revision of mass-loss rate predictions in hot massive stars (Krtička & Kubát 2017;Sundqvist et al 2019;Gormaz-Matamala et al 2022). Together with observational indications of lower mass-loss rates in massive stars (e.g., Šurlan et al 2013;Kobulnicky et al 2019;Brands et al 2022), this challenges our current understanding of massive star evolution.…”

“…(3), albeit with stronger effect. Analogous but steeper metallicity variations were found by Gormaz-Matamala et al (2022). Vink & Sander (2021) predict the metallicity dependence of mass-loss rates as Ṁ ∼ Z 0.42 above the bistability jump and Ṁ ∼ Z 0.85 below the jump.…”

Delayed Massive-star Mechanical Feedback at Low Metallicity

“…Mass-loss rates obtained from Hα and UV absorption features reveal values that are smaller than theoretical mass-loss rates from, e.g., Vink et al (2001) by a factor of ∼3 (Puls et al 2008;Bouret et al 2012;Šurlan et al 2013). Recent numerical models continue to support this moderate decrease (e.g., Vink & Sander 2021;Gormaz-Matamala et al 2022). However, recent studies that account for wind microclumping and weak winds show a much more dramatic decrease from Vink et al's (2001) formula of up to one, or even two, orders of magnitude (Ramachandran et al 2019;Rickard et al 2022;Björklund et al 2023).…”

On the Maximum Black Hole Mass at Solar Metallicity

“…For optically thin winds we adopt the mass-loss rate from Gormaz-Matamala et al (2022b), based on their self-consistent m-CAK prescription (Gormaz-Matamala et al 2019, 2022a…”