\begin{center}{\Large\bf 
Wind Models for Very Massive Stars in the Local Universe}\end{center} 

\centerline{\bf Jorick S. Vink (Armagh), J. M. Bestenlehner (Armagh), G. Graefener (Armagh), A. de Koter (Amsterdam), N. Langer (Bonn)
}{\footnotesize Armagh Observatory
}
 
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.

{\bf Reference: To appear in Four Decades of Research on Massive Stars, ASP Conf. Ser.} \\{\it Status:} Conference proceedings
 \\ {\it Comments:} 

{\it On the web at:} {\tt http://arxiv.org/abs/1112.0936} 

{\it Preprints from:} {\tt  jsv@arm.ac.uk} 
\vspace*{5mm} 

