The pulsation properties of DB white dwarfs : a preliminary analysis.

Abstract

Preliminary numerical results are given for the nonradial g-mode pulsation properties of evolutionary DB white dwarf models, where the solutions include the fully nonadiabatic equations for modes corresponding to the spherical harmonic index l = 1-3. For each of the model sequences examined, a nonradial g-mode instability strip approximately 3000 K wide is found which, for models with standard ML1 convection, lies in the 16,000-19,000 effective temperature range. The instability strip boundaries are so sensitive to the assumed convection efficiency that, for sequences with more efficient convection, the instability strip lies between 26,000 and 29,000 K effective temperatures. The extrapolation of these 0.6 solar mass calculations to 0.4 and 0.9 solar masses indicates that the instability strip boundaries are insensitive to uncertainties in the total stellar mass.