New nonadiabatic pulsational computations on full PG1159 evolutionary models: the theoretical GW Virginis instability strip revisited

CORSICO, A. H.; ALTHAUS, L. G.; MILLER BERTOLAMI, M. M

ASTRONOMY AND ASTROPHYSICS

EDP Sciences

Año: 2006 vol. 458 p. 259 - 267

0004-6361

Aims: We reexamine the theoretical instability domain of pulsating PG 1159 stars (GW Vir variables). Methods: We performed an extensive g-mode stability analysis on PG 1159 evolutionary models with stellar masses ranging from 0.530 to 0.741 Msun , for which the complete evolutionary stages of their progenitors from the ZAMS, through the thermally pulsing AGB and born-again phases to the domain of the PG 1159 stars have been considered. Results.We found that pulsations in PG 1159 stars are excited by the kappa mechanism due to partial ionization of carbon and oxygen, and that no composition gradients are needed between the surface layers and the driving region, much in agreement with previous studies. We show, for the first time, the existence of a red edge of the instability strip at high luminosities. We found that all of the GW Vir stars lay within our theoretical instability strip. Our results suggest a qualitative good agreement between the observed and the predicted ranges of unstable periods of individual stars. Finally, we found that generally the seismic masses (derived from the period spacing) of GWVir stars are somewhat different from the masses suggested by evolutionary tracks coupled with spectroscopy.