Hydrodynamical mass-loss rates for very massive stars II. New theoretical mass-loss predictions at solar metallicity (Z = 0.02)

2026/07/30 by Gautham N. Sabhahit, Jorick S. Vink, Andreas A. C. Sander
Physics and Astronomy · #astro-ph.SR #astro-ph.GA #astro-ph.HE

paper · pdf

Accepted in A&A (30th July), 12 pages, 12 figures, 3 tables, 3 appendices

arxiv created 2026/07/30 · arxiv updated 2026/07/31

Abstract

The evolutionary pathways and ultimate fates of very massive stars are governed primarily by mass loss through radiatively-driven winds. We present a new theoretical mass-loss prescription for (very) massive stars, capturing the complex dependence on the Eddington parameter Γ_e, luminosity, temperature, and hydrogen abundance. We calculated an extensive grid of 178 hydrodynamically consistent wind-atmosphere models in non-local thermodynamic equilibrium using the PoWR-HD code, predicting wind properties such as the mass-loss rate and terminal velocity self-consistently. The grid spans masses M_* = 16-500 Msun, luminosities log(L_*/L_\odot) = 5.5-6.8, inner boundary temperatures T_* = 12-50 kK, and hydrogen mass fractions X = 0.01-0.9, at a fixed metallicity of Z=0.02. We confirm the presence of a mass-loss kink in the M-Γ_e relation across the explored parameter space. The kink marks the transition from a shallow scaling (∼ 2.8) at low Γ_e for optically thin O-star winds to a steeper scaling (∼ 10) for optically thick winds at high Γ_e. We derive comprehensive fitting relations capturing both the kink behaviour and two bistability jumps arising from iron ionisation changes, and provide auxiliary relations for implementation into stellar evolutionary calculations. Our prescription correctly reproduces the model-independent transition mass-loss rate in the Arches Cluster, confirming the accuracy of our predicted rates at the O-to-WNh transition. Application of our recipe to the Zero Age Main Sequence provides excellent agreement with recent empirical M-Γ_e relation obtained for a wide range of temperatures and Eddington parameters. We provide a physically motivated, continuous, and empirically anchored mass-loss recipe for (very) massive stars, suitable for stellar evolution calculations in the 20-500 Msun range.

Related

• Hydrodynamical mass-loss rates for Very Massive Stars. I. Investigating the wind kink
• New empirical mass-loss recipe for UV radiation line-driven winds of hot stars across various metallicities
• New predictions for radiation-driven, steady-state mass-loss and wind-momentum from hot, massive stars III. Updated mass-loss rates for stellar evolution
• Wind Models for Very Massive Stars in the Local Universe
• Near-Eddington mass loss of hydrogen-rich Wolf-Rayet stars