Static and dynamic spherical stellar atmospheres applied to optical interferometry

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The quantitative study of stars has been one of the major successes of astrophysics, and it is transitioning to even higher levels thanks to tranformative improvements in imaging stellar surfaces, measuring stellar brightnesses to 1 part per million and determining stellar distances to a fraction of 1%. To interpret these data, we have developed a robust computer program to represent spherical stellar atmospheres characterized by their three fundamental parameters: luminosity, mass and radius. Using existing data for luminosities and radii, we are able to derive the masses of single stars, which puts meaningful limits on the star's age. We are extending this computer program to incorporate radial pulsation in order to apply it to the important Cepheid variable stars, which are essential for measuring distances beyond the Milky Way. These numerical models will give us a much deeper understanding of the Cepheid variables, as well as enabling us to investigate our previous analytic result that pulsation drives mass from Cepheids, affecting both the observations and our interpretation of the life histories of these stars.