ADIABATIC PROPERTIES OF PULSATING DA WHITE-DWARFS .3. A FINITE-ELEMENT CODE FOR SOLVING NONRADIAL PULSATION EQUATIONS

We present a new numerical code to solve the system of ordinary differential equations which describes the linear, adiabatic, nonradial pulsations of stellar models. This code, based on the Galerkin finite-element method of weighted residuals, is characterized by its stability, speed, accuracy, high-order convergence, and ease of use. Its performance is illustrated in tests carried out both with a homogeneous, polytropic stellar model and with a realistic stellar evolution model. It is also contrasted with the performance of two other codes, previously used in adiabatic studies of pulsating DA white dwarfs, which are based on either relaxation or shooting methods. The finite-element code outperforms both of them in terms of accuracy, effectiveness, and stability.