The Stellar Seismology of the Hot White Dwarf Star PG1159-035

Abstract

Asymptotic analysis of the equations of nonradial adiabatic oscillation shows that there is a “characteristic period spacing” for g-modes with the same degree (l) and consecutive values of the radial wavenumber (n). If modes with the same l but different n are present in a pulsating star, then comparison of the characteristic period spacing in appropriate stellar models with period differences between the observed pulsation periods can provide mode identifications, and thereby constrain other physical properties of the star. A simple empirical model of the observed period spectrum of the hot white dwarf star PG1159-035 yields two statistically significant mean period intervals of 21.0±0.3 or 8.8±0.1s. We also evaluate the period interval for models of hot white dwarfs that are representative of PG1159 stars. The observed intervals correspond very closely to those derived from the theoretical models. This analysis indicates that the mass of PG1159-035 is 0.60M_⊙ and that it is either a dipole (l=1) or l=3 pulsator (or both!), pulsating in high radial overtone g-modes.