Wind Models for Very Massive Stars in the Local Universe

TL;DR

This paper presents new mass-loss models for very massive stars up to 300 Msun, revealing a transition in wind properties near the Eddington limit, which impacts the understanding of the stellar upper-mass limit.

Contribution

It introduces a novel dynamical approach to predict mass loss in very massive stars, resolving the transition from optically thin to thick winds near the Eddington limit.

Findings

Identified a 'kink' in mass-loss versus Gamma relation at wind optical thickness transition.

First models to resolve the transition from O-star to Wolf-Rayet star winds.

Suggests the stellar upper-mass limit could exceed 200 Msun.

Abstract

Some studies have claimed the existence of a stellar upper-mass limit of 150 Msun. A factor that is often overlooked concerns the issue that there might be a significant difference between the present-day and the initial mass of the most massive stars - as a result of mass loss. The upper-mass limit may be substantially higher, possibly exceeding 200 Msun. The issue of the upper mass-limit will however remain uncertain as long as there is only limited quantitative knowledge of mass loss in close proximity to the Eddington (= Gamma) limit. For this reason, we present mass-loss predictions from Monte Carlo radiative transfer models for very massive stars up to 300 Msun. Using our new dynamical approach, we find an upturn or "kink" in the mass-loss versus Gamma dependence, at the point where our model winds become optically thick. These are the first mass-loss predictions where the transition from optically thin O-star winds to optically thick Wolf-Rayet winds has been resolved.