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D. Proga (NASAs GSFC)
I summarize the essential concepts underpinning models of radiation-driven winds from variety of stellar environments. Stars, and disks that often surround them, appear to loss mass during their entire life although at rates and in ways that depend on the evolutionary stage. As we know about stars/disks mostly through observations of their radiation we can put firm constrains on what is the amount of energy and momentum in the radiation. In many cases, the momentum in the radiation scales with and is comparable to that in the winds. One of the critical aspects of radiation driving then is how the radiation momentum can be transfered to the matter. As the temperature of the matter increases, radiation pressure can be predominately mediated by dust opacity, bound-free opacity, bound-bound opacity and electron opacity. Thus dealing with radiation-driven winds we face one of the basic problem in astrophysics: the radiation transfer problem. In this review, I will illustrate how the radiation force can explain launching and acceleration of bipolar winds at early and late stages of stellar evolution.
This work was performed while the author held a National Research Council Research Associateship at NASA/GSFC.