New-nonadiabatic-pulsation-computations-on-full-PG1159-evolutionary-models-the：theoretical-GW-Vir-instability-strip-revisited.pdfVIP

Astronomy Astrophysics manuscript no. paper-pg July 4, 2006 (DOI: will be inserted by hand later) New nonadiabatic pulsation computations on full PG1159 evolutionary models: the theoretical GW Vir instability strip revisited A. H. C´orsico1,2⋆ , L. G. Althaus1,2⋆ and M. M. Miller Bertolami1,2,3⋆⋆ 1 Facultad de Ciencias Astron´omicas y Geof´ısicas, Universidad Nacional de La Plata, Paseo del Bosque S/N, (1900) La Plata, Argentina. 2 Instituto de Astrof´ısica La Plata, IALP, CONICET-UNLP 3 Max-Planck-Institut f¨ur Astrophysik, Garching, Germany e-mail: acorsico,althaus,mmiller@fcaglp.unlp.edu.ar Received; accepted Abstract. 1. Background in a hot white dwarf shortly after hydrogen burning has almost ceased (see Fujimoto 1977; Sch¨onberner 1979 and Pulsating PG1159 stars — after the prototype of the spec- more recently Althaus et al. 2005) or a late helium thermal tral class and the variable type, PG 1159-035 or GW Vir pulse (LTP) that takes place during the post-AGB evolu- — are very hot hydrogen-deficient post-Asymptotic Giant tion when hydrogen burning is still active (see Bl¨ocker Branch (AGB) stars with surface layers rich in helium 2001 for references). During a VLTP episode, most of the (∼ 30−85%), carbon (∼ 15−60%) and oxygen (∼ 2−20%) hydrogen-rich envelope of the star is burnt in the helium- (Werner Herwig 2006) that exhibit multiperiodic, low flash convection zone, whilst in a LTP hydrogen-deficient degree (ℓ ≤ 2), high radial order (k