Wind Models for Very Massive Stars in the Local Universe
  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.
