Nonlinear Coupling between Pulsation and Convection in Late Type Stars
Abstract
A simple idealized nonlinear model applicable to long period variable stars has been formulated that assumes the convective envelope ofM giants is composed of giant convection cells, which are comparable in size to the stellar radius. The simplicity of this model essentially constitutes a physical analog to the strong dynamic coupling that occurs if the convective envelope of the star undergoes both modes of motion. As shown implicitly in the time scales associated with these motions, the coupling produces asymmetrical fluctuations of the entire star, the mean velocity of which is comparable to the escape velocity of the star at particular values of the ratio of the pulsation and convection time scales. It is suggested that this can account for the mass loss from late type stars, and the circumstellar dust shells that are associated extensively with long period variables. For critical values of the pulsation and convection time scales, the solutions correspond to the rapid expansion of the entire convective envelope, and is the basis of a new mechanism that simulates the manner in which pulsating stars ballistically accelerate their convective shells to form planetary nebulae.
 Publication:

Astrophysics and Space Science
 Pub Date:
 November 1976
 DOI:
 10.1007/BF00642153
 Bibcode:
 1976Ap&SS..45..175A
 Keywords:

 M Stars;
 Pulsars;
 Red Giant Stars;
 Stellar Envelopes;
 Stellar Models;
 Variable Stars;
 Nonlinear Equations;
 Planetary Nebulae;
 Stellar Mass Ejection;
 Supergiant Stars;
 Astrophysics