AN ADAPTIVE CODE FOR RADIAL STELLAR MODEL PULSATIONS

We describe an implicit 1-D adaptive mesh hydrodynamics code that is s pecially tailored for radial stellar pulsations. In the Lagrangian lim it the code reduces to the well tested Fraley scheme. The code has the useful feature that unwanted, long lasting transients can be avoided by smoothly switching on the adaptive mesh features starting from the Lagrangean code. Thus, a limit cycle pulsation that can readily be com puted with the relaxation method of Stellingwerf will converge in a fe w tens of pulsation cycles when put into the adaptive mesh code. The c ode has been checked with two shock problems, viz. Noh and Sedov, for which analytical solutions are known, and it has been found to be both accurate and stable. Superior results were obtained through the solut ion of the total energy (gravitational + kinetic + internal) equation rather than that of the internal energy only.