Mira Variables

Lee Anne Willson (Iowa State University)

Abstract:

I will stress the interpretation of observations of Miras from a variety of different perspectives. First, I will review the Mira stage of evolution and the role of the associated mass loss in stripping giants of their envelopes. This analysis confirms deductions from other arguments concerning the probable radii and pulsation modes of Miras. Second, I will discuss what theoretical models tell us about the likely structure of a Mira's atmosphere and wind, and what we may be seeing when we look at high angular resolution. Third, I will suggest a number of factors that could lead to real or apparent departures from circular (spherical) symmetry in the observed brightness distribution. Finally, I will suggest some ways in which different hypotheses might be tested using data from interferometry in conjunction with other data about the individual stars and the class of Miras.

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Reference:

• Mass loss from cool stars:impact on the evolution of stars and stellar populations
  L.A. Willson
  Ann. Rev. Astron. Astrophys. 38, 573-611 (2000).