Evolution of Stars with 60 and 200 Msun: Predictions for WNh Stars in the Milky Way

We study in detail the evolution of two massive stars at solar metallicity (Z=0.014) taken from Romagnolo et al. (2024, Paper I); by running evolution models for initial masses 60 and 200 Msun, using MESA and GENEC. For the mass loss, we adopt the self-consistent m-CAK prescription for the optically thin winds of OB-stars, a semi-empirical formula for H-rich thick wind of WNh stars, and a hydrodynamically consistent formula for the H-poor thick wind of classical Wolf-Rayet stars. We set initial rotation as 40 angular velocity, overshooting =0.5, Tayler-Spruit for the angular momentum transport, and Ledoux criterion for the convective layers. Both codes predict different tracks across the HRD. For the 60 Msun case, Genec models predict a more efficient rotational mixing and more chemically homogeneous evolution, whereas MESA model predicts a large radial expansion post-MS reaching the LBV phase. For the 200 Msun case, differences are less relevant because their evolution is dominated by wind mass loss with a weaker dependence on internal mixing, and only the treatment for superadiabacity creates an impact during the He-burning stage. The switch of the mass loss based on the proximity to 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 formed from initial masses ≳60 Msun. These stars are constrained in a Teff range of the HR diagram which corresponds to the MS band, in agreement with the observations of Galactic WNh stars. While our models employ a fixed Γ_e threshold for the switch to thick winds, rather than a continuous thin-to-thick wind model, the good reproduction of observations supports the robustness of the wind model upgrades introduced in Paper I, allowing its application to studies of late-stage stellar evolution before core collapse.