July 11-15, 2011
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Wind models for very massive stars up to 300 solar masses

Jorick Vink (Armagh Observatory)

Lianne Muijres, Alex de Koter (Amsterdam), Goetz Graefener (Armagh Observatory), Norbert Langer (Bonn)

The stellar upper-mass limit is highly uncertain. Some studies have claimed the existence of a universal upper limit of 150 solar masses. 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 thus easily supercede 200 solar masses. The issue of the upper mass-limit however remains 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 new mass-loss predictions from Monte Carlo radiative transfer models for very massive stars up to 300 solar masses. 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 between the optically thin O-star winds and the optically thick Wolf-Rayet winds has been resolved.
(to be confirmed by the SOC)