On the excitation of PG 1159-type pulsations

Abstract

Abstract. Stability properties are presented of dipole and quadrupole nonradial oscillation modes of model stars that experienced a late helium shell flash on their way to the white-dwarf cooling domain. The computed instability domains are compared with the observed hot variable central stars of planetary nebulae and the GW Vir pulsators.

Can pulsating PG 1159 stars place constraints on the occurrence of core overshooting?

“…We limited our calculations to the degrees = 1, 2 because the periods observed in pulsating PG 1159 stars have been identified 1 The stellar models have also recently been employed in Gautschy et al (2005) for nonadiabatic pulsation studies of PG 1159 stars. To get values of periods as precise as possible, we have employed about 2700−3000 mesh-points to describe our background stellar models.…”

“…Over the years, considerable observational effort has been devoted to demonstrating the occurrence of core overshooting. Indeed, confrontation of stellar models with a wide variety of observational data suggests that convective overshoot takes place in real stars (see Stothers & Chin 1992;Alongi et al 1993;Kozhurina-Platais et al 1997;Herwig et al 1997;von Hippel & Gilmore 2000, among others).…”

White Dwarf and Pre-White Dwarf Pulsations

“…This was first shown to be a viable explanation for the pulsations in the DOVs by Saio [21] and Gautschy [22]. Since then more refined calculations have been made which strengthen this result [23,24,22,21]. Figure 8 shows the distribution of known variable and non-variable PG1159 stars in the Tgff-log^ plane, with the theoretical boundaries of the instability strip as calculated by C6rsico et al [20].…”

Astrophysics in 2005

“…Then arrived the PG 1159 stars, with mostly CϩO, which they retain, until gravitational settling changes them to DOs and DAs (Gautschy et al 2005, a pulsation calculation). They are also allowed a bit of H or He if they want (Vauclair et al 2005, also on pulsations).…”