Computational astrophysics: Pulsating stars
Abstract
The field of computational astrophysics in pulsating star studies has grown considerably since the advent of the computer. Initially calculations were done on the IBM 704 with 32K of memory and now we use the CRAY YMP computers with considerably more memory. Our early studies were for models of pulsating stars using a 1D Lagrangian hydrodynamic code (SPEC) with radiation diffusion. The radiative transfer was treated in the equilibrium diffusion approximation and the hydrodynamics was done utilizing the approximation of artificial viscosity. The early calculations took many hours of 704 CPU time. Early in 1965 we decided to improve on the usual treatment of the radiative transfer used in our codes by utilizing the method of moments, the socalled variable Eddington approximation. In this approximation the material energy field is uncoupled from the radiation energy field and the angular dependence is introduced through the Eddington factor. A multigroup frequency dependent method may also be applied. The Eddington factor is determined by snapshots of the stars structure utilizing a yline approximation. The full radiative transfer approximation appears necessary in order to understand the light curves for W Virginia stars and may be important for the light curves of RR Lyrae stars. A detailed radiative transfer method does not appear to be necessary for the understanding of Cepheid light curves. A recent improvement to our models for pulsating stars is in the use of an adaptive mesh scheme to resolve the sharp features in the nonlinear hydrodynamic structure. From these improved structures, better analysis of the radius, velocity, and light curves could be obtained.
 Publication:

Presented at the 2nd International Conference on Computational Physics
 Pub Date:
 1993
 Bibcode:
 1993coph.conf...13D
 Keywords:

 Computational Astrophysics;
 Light Curve;
 Pulsars;
 Radiative Transfer;
 Stellar Models;
 Stellar Radiation;
 Cepheid Variables;
 Eddington Approximation;
 Lyra Constellation;
 Method Of Moments;
 Radiation Distribution;
 Radiation Transport;
 WolfRayet Stars;
 Astrophysics