Massive Wolf-Rayet and other hot stars |
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The Wolf-Rayet stellar evolution phase,
represents the end stage of the life of massive stars.
During this period a strong dense stellar wind ejects mass from the
stellar surface at a large rate. This accelerates the star towards the
instability that will eventually result in the star exploding as a supernova.
The observed mass-loss rates that characterize the Wolf-Rayet wind cannot be explained though a radiation-driven wind theory. A lot of effort has been spent in the search for an efficient mechanism that can remove mass from the star at the observed rates. It has been demonstrated that if the ionization structure of the wind can be altered to obtain a more stratified layout of the different ions, then the interaction of radiation with matter can be made more efficient. Following this line of investigation Werner Schmutz (Schmutz 1997) has proposed a way to obtain such structure though the capture of photons in the proximity of the HeI Ly alpha line by calcium and iron line opacity. This mechanism, termed "photon loss" lies at the center of my investigation. My most influential work in this field has been on the characterization of the WC8+O7.5 binary system Gamma Velorum. We developped non-LTE atmospheric models for both the O and Wolf-Rayet stars. The first part of the work ( De Marco & Schmutz 1999) developed a model for the O star which incorporated the determination of the light ratio between the O and Wolf-Rayet stellar components. The second part of the work ( De Marco et al. 2000) is involved with the Wolf-Rayet star. These two models are used today as the basis of models that attempt at characterizing the wind-wind interaction between the two stars. |
Last Update: 22 December 2006