Direct Measurement of a Secular Pulsation Period Change in the Pulsating Hot Pre–White Dwarf PG 1159−035

Abstract

GW Vir (PG 1159-035) is the prototype of the class of multiperiodic, nonradially pulsating hot white dwarfs, and shows a strong pulsation mode at 516 s. All measurements to date of the secular variation of the 516 s pulsation quote as best value = (-2.49 ± 0.06) × 10-11 s s-1. The original measurement gave two best solutions, and a χ2 analysis indicated that the quoted value was preferred at the level of 0.97 probability. On other hand, the best-developed models for planetary nebula nuclei (PNNs), using models from the asymptotic giant branch as starting points and simulating the observed mass loss, provide positive values for any model with log(L/L☉) ≲ 3, as PG 1159-035. This conflict between the measurement and the theoretical models has been a challenge to stellar evolution theory.