Dynamical Phenomena in Pulsating Star Atmospheres

Abstract

Progress in numerical modeling of the structure and behavior of the dynamical atmospheres of pulsating stars, especially the cool long-period variables, will be reviewed. Compared to an atmosphere in static equilibrium, the dynamic atmosphere typically is greatly extended, with a very different density and temperature distribution. The atmospheric chemistry is affected. The star’s spectrum is affected. Shock waves are always present. Dust may form, in some cases in large amount. Outflowing winds typically develop, with mass loss rates which can be very large. Partial transmission of acoustic waves into the atmosphere can effectively drain substantial amounts of energy from the interior oscillations. These effects involve nonlinear, time-dependent processes which often are not in equilibrium and which interact in complex ways. Modeling these dynamical phenomena satisfactorily is thus not easy, but it must be done, for the atmosphere of a pulsating star does play an important part in determining the behavior of the star.