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Session 96 - Cepheids and Supergiant Variable Stars.
Display session, Thursday, January 16
Metropolitan Ballroom,
Detailed calculations of the mass loss process for pulsating red giants illustrate clearly the pitfalls in the use of empirical mass loss laws, including the popular Reimers' relation and the more recently developed relation for long period variables by Vassiliadis and Wood (Ap. J., 413, 641). When studied in detail, mass loss rates prove very sensitive to stellar parameters. Empirical relations are then necessarily subject to very large selection effects. It is also generally difficult or impossible to sort out the dependence of mass loss rates on masses for the stars with observed mass loss rates. Finally, the importance of mass loss in populations not available for empirical study (such as young, low metallicity stars) cannot be estimated accurately from observations of stars in our galaxy. The situation with respect to the inclusion of mass loss into stellar evolution calculations today is analogous to the situation of stellar evolution modeling when the main sequence was widely regarded to be an evolutionary track. Just as detailed calculations of stellar evolution models removed that misconception, detailed studies of the mass loss process from a variety of classes of stars will be needed to provide reliable rules for use in evolutionary modeling. Mass loss plays a key role in several features that determine the appearance of clusters and populations, and thus affect distance and age determinations.
