Pulsational stability of stars in thermal imbalance. VI. Physical mechanisms and extension to nonradial oscillations

view Abstract Citations (14) References (6) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Pulsational stability of stars in the thermal imbalance. VI. Physical mechanisms and extension to nonradial oscillations. Aizenman, M. L.; Cox, J. P. Abstract A clarification of the physical mechanisms operative in the pulsational stability against radial oscillations of spherical stars in thermal imbalance is presented. It is shown that the stability coefficient for such stars can be conceptually separated into distinct "dynamical" and "nonadiabatic" parts. The dynamical part involves no nonadiabatic effects, and is analogous to a slowly time-varying spring consVant in a simple mechanical system. The nonadiabatic part arises from phase shifts between the pressure and density variations brought about solely by the small nonadiabatic effects which cannot be neglected in a star in thermal imbalance. This separation permits a clear and simple physical interpretation of the expression for the stability coefficient for quasiadiabatic oscillations of a certain class of stellar models (which does not assume homologous secular motion), and serves as a valuable guide for attacking problems involving thermal imbalance effects in more complicated cases of stellar oscillations. It is shown with the help of this guide that the formal expression for the stability coefficient for purely radial oscillations also applies identically to the nonradial oscillations of a spherical star in thermal imbalance. We suggest that these thermal imbalance effects as applied to nonradial oscillations may play a role in the instability of the p Cephei stars. Subject headings: pulsation - stellar evolution - p Cephei stars Publication: The Astrophysical Journal Pub Date: January 1975 DOI: 10.1086/153316 Bibcode: 1975ApJ...195..175A Keywords: Dynamic Stability; Stellar Evolution; Thermodynamic Equilibrium; Variable Stars; Adiabatic Conditions; Differential Equations; Heat Flux; Linear Equations; Linearization; Operators (Mathematics); Velocity Distribution; Astrophysics full text sources ADS |