Pulsation and mass loss in Mira variables

Abstract

The behavior of pulsation in the outer layers of a typical Mira variable was studied in the adiabatic and isothermal limits. A shock wave propagates outward once per period and the radial velocity obtained from observations of hydrogen emission lines is identified with the velocity of gas in the post shock region. In the adiabatic case, mass loss in the form of a steady stellar wind was produced. In the isothermal case, no continuous mass loss was produced but occasional ejection of shells occur. Pulsation introduced into a star undergoing steady mass loss as a result of radiation pressure acting on grains caused the mass loss rate to increase by a factor of approximately 40, while the terminal velocity of the flow was almost unaltered