Evolution of stars with 60 and 200

Context. Massive stars are characterised by powerful stellar winds driven by radiation; thus, the mass-loss rate is known to play a crucial role in their evolution. Aims. We study the evolution of two massive stars (a classical massive star and a very massive star) at solar metallicity (Z = 0.014) in detail. We calculate their final masses, radial expansion, and chemical enrichment, at their H-core, He-core, and C-core burning stages, prior to their final collapse. Methods. We ran evolutionary models for initial masses of 60 and 200 M⊙ using <ns0:monospace>MESA</ns0:monospace> and the Geneva-evolution-code (G<ns0:sc>ENEC</ns0:sc>). For the mass loss, we adopted the self-consistent m-CAK prescription for the optically thin winds of OB-type stars, a semi-empirical formula for H-rich optically thick wind of luminous Wolf-Rayet (WR) stars of the nitrogen sequence with hydrogen in their spectra (WNh stars), and a hydrodynamically consistent formula for the H-poor thick wind of classical WR stars. The transition from thin to thick winds was set to Γe = 0.5. Results. The unification of the initial set-up for the stellar structure and wind prescription leads to very similar black hole mass for both G<ns0:sc>ENEC</ns0:sc> and <ns0:monospace>MESA</ns0:monospace> codes, but both codes predict different tracks across the Hertzsprung-Russell diagram (HRD) For the 60 M⊙ case, the G<ns0:sc>ENEC</ns0:sc> model predicts a more efficient rotational mixing and more chemically homogeneous evolution, whereas the <ns0:monospace>MESA</ns0:monospace> model predicts a large radial expansion that reaches the Luminous Blue Variable (LBV) phase. For the 200 M⊙ case, differences between both evolution codes are less relevant because their evolution is dominated by wind mass loss with a weaker dependence on internal mixing. Conclusions. The switch of the mass-loss prescription based on the Eddington factor instead of the removal of outer layers, implies the existence of WNh stars with a large mass fraction of hydrogen at the surface (Xsurf ≥ 0.3) formed from initial masses of ≳60 M⊙. These stars are constrained in a Teff range of the HRD which corresponds to the main sequence band, in agreement with the observations of Galactic WNh stars at Z = 0.014. While our models employ a fixed Γe, trans threshold for the switch to thick winds, rather than a continuous thin-to-thick wind model, the good reproduction of observations during the main sequence supports the robustness of the wind model upgrades, allowing its application to studies of late-stage stellar evolution before core collapse.

Publication Details

Journal
Springer Link (Chiba Institute of Technology)
Published
2025-04-04
DOI
https://doi.org/10.1051/0004-6361/202451565/pdf
Primary Topic
Stellar, planetary, and galactic studies
Type
article
Field-Weighted Citation Impact
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article

Evolution of stars with 60 and 200

Springer Link (Chiba Institute of Technology)
Stellar, planetary, and galactic studies
article

Evolution of stars with 60 and 200

article en

Abstract

Context. Massive stars are characterised by powerful stellar winds driven by radiation; thus, the mass-loss rate is known to play a crucial role in their evolution. Aims. We study the evolution of two massive stars (a classical massive star and a very massive star) at solar metallicity (Z = 0.014) in detail. We calculate their final masses, radial expansion, and chemical enrichment, at their H-core, He-core, and C-core burning stages, prior to their final collapse. Methods. We ran evolutionary models for initial masses of 60 and 200 M⊙ using <ns0:monospace>MESA</ns0:monospace> and the Geneva-evolution-code (G<ns0:sc>ENEC</ns0:sc>). For the mass loss, we adopted the self-consistent m-CAK prescription for the optically thin winds of OB-type stars, a semi-empirical formula for H-rich optically thick wind of luminous Wolf-Rayet (WR) stars of the nitrogen sequence with hydrogen in their spectra (WNh stars), and a hydrodynamically consistent formula for the H-poor thick wind of classical WR stars. The transition from thin to thick winds was set to Γe = 0.5. Results. The unification of the initial set-up for the stellar structure and wind prescription leads to very similar black hole mass for both G<ns0:sc>ENEC</ns0:sc> and <ns0:monospace>MESA</ns0:monospace> codes, but both codes predict different tracks across the Hertzsprung-Russell diagram (HRD) For the 60 M⊙ case, the G<ns0:sc>ENEC</ns0:sc> model predicts a more efficient rotational mixing and more chemically homogeneous evolution, whereas the <ns0:monospace>MESA</ns0:monospace> model predicts a large radial expansion that reaches the Luminous Blue Variable (LBV) phase. For the 200 M⊙ case, differences between both evolution codes are less relevant because their evolution is dominated by wind mass loss with a weaker dependence on internal mixing. Conclusions. The switch of the mass-loss prescription based on the Eddington factor instead of the removal of outer layers, implies the existence of WNh stars with a large mass fraction of hydrogen at the surface (Xsurf ≥ 0.3) formed from initial masses of ≳60 M⊙. These stars are constrained in a Teff range of the HRD which corresponds to the main sequence band, in agreement with the observations of Galactic WNh stars at Z = 0.014. While our models employ a fixed Γe, trans threshold for the switch to thick winds, rather than a continuous thin-to-thick wind model, the good reproduction of observations during the main sequence supports the robustness of the wind model upgrades, allowing its application to studies of late-stage stellar evolution before core collapse.

Springer Link (Chiba Institute of Technology)
Openalex Percentile: Top 71%
Stellar, planetary, and galactic studies
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