Influence of Opacity on the Pulsational Stability Of Massive Stars with Uniform Chemical Composition

Authors

Richard Stothers, Goddard Institute for Space Studies
Norman R. Simon, University of Nebraska - LincolnFollow

Document Type

Article

Date of this Version

6-1970

Citation

THE ASTROPHYSICAL JOURNAL, Vol. 160, June 1970

Comments

Copyright 1970. The University of Chicago. All rights reserved.

Abstract

The maximum mass of homogeneous stars which are stable against nuclear-energized pulsations has been re-determined by using a full opacity formula and an accurate treatment of the equilibrium structure of the outer layers where non-scattering sources of opacity are important damping agents. Sixteen composition mixtures were used, covering the range 0 ≤ Y ≤ (1 - Z) and 0 ≤ Z ≤ 0.05. The nuclear energy sources were taken to be the CN cycle and the triple-a process. Due to the primary influence of bound-free absorption by metals (and, to a lesser extent, of free-free absorption by hydrogen and helium), the critically stable non-dimensional mass of hydrogen-burning stars, (M/M_ʘ)μ², can range from 27 to 94, depending on the chemical composition. For likely chemical compositions of extreme Population I, the actual critical mass is probably 80-120 M _ʘ. For homogeneous helium-burning stars, the critical mass ranges from 13 to 19 M _ʘ, depending on the metal abundance.