On adaptive grid computations of variable stars
Abstract
We show that the use of an implicit adaptivegrid technique is an efficient and uptodate approach for the calculations of radial oscillations in variable stars. We chose as an illustrative example the radiative envelope of an RR Lyrae variable. For the hydrostatic initial model we compare the Lagrangean ratioed zoning with an adaptivegrid rezoning. We show that the adaptivegrid yields an optimal distribution of the mesh points in the sense that the relevant physical features, the H and He 1, He 2ionization zones, are well resolved. For the hydrodynamical evolution we present the fullamplitude model for both the Lagrangean and adaptivegrid computations. We perform a detailed comparison and show that the adaptivegrid method yields limit cycle solutions that are substantially improved over the Lagrangean grid model. This is due to the fact that the Lagrangean mesh sweeps through the ionization zones twice during one oscillation period, whereas the adaptivemesh resolves them and tracks them continuously. The results are, in particular, smooth radial velocity and light curves. Beyond a physically better defined solution we also observe larger time steps for the convergence towards the limit cycle and for the evolution during one period.
 Publication:

Presented at the 11th Annual Center for Nonlinear Studies (CNLS) Conference
 Pub Date:
 1991
 Bibcode:
 1991cnls.conf...20C
 Keywords:

 Computational Grids;
 Hydrodynamics;
 Hydrostatics;
 Stellar Models;
 Stellar Oscillations;
 Variable Stars;
 Convergence;
 Ionization;
 Radial Velocity;
 Astrophysics