New evolutionary models for massive ZZ Ceti stars. I. First results for their pulsational properties
Open Access
- 2 June 2003
- journal article
- Published by EDP Sciences in Astronomy & Astrophysics
- Vol. 404 (2), 593-609
- https://doi.org/10.1051/0004-6361:20030472
Abstract
We present new and improved evolutionary calculations for carbon-oxygen white dwarf (WD) stars appropriate for the study of massive ZZ Ceti stars. To this end, we follow the complete evolution of massive WD progenitors from the zero-age main sequence through the thermally pulsing and mass loss phases to the WD regime. Abundance changes are accounted for by means of a full coupling between nuclear evolution and time-dependent mixing due to diffusive overshoot, semiconvection and salt fingers. In addition, time-dependent element diffusion for multicomponent gases has been considered during the WD stage. Emphasis is placed on the chemistry variations along the whole evolution. In particular, we find that before the ZZ Ceti stage is reached, element diffusion has strongly smoothed out the chemical profile to such a degree that the resulting internal abundance distribution does not depend on the occurrence of overshoot episodes during the thermally pulsing phase. The mass of the hydrogen envelope left at the ZZ Ceti domain amounts to 2.3 . This is about half as large as for the case when element diffusion is neglected. The implications of our new models for the pulsational properties of massive ZZ Ceti stars are discussed. In this regard, we find that the occurrence of core overshooting during central helium burning leaves strong imprints on the theoretical period spectrum of massive ZZ Ceti stars. Finally, we present a simple new prescription for calculating the He/H profile which goes beyond the trace element approximation.Keywords
This publication has 43 references indexed in Scilit:
- Evolution of a 3-M⊙star from the main sequence to the ZZ Ceti stage: the role played by element diffusionMonthly Notices of the Royal Astronomical Society, 2002
- Asteroseismological Constraints on the Structure of the ZZ Ceti Stars L19‐2 and GD 165The Astrophysical Journal, 2001
- Diffusion in helium white dwarf starsMonthly Notices of the Royal Astronomical Society, 2000
- A compilation of charged-particle induced thermonuclear reaction ratesNuclear Physics A, 1999
- Asteroseismological Constraints on the Structure of the ZZ Ceti Stars G117‐B15A and R548The Astrophysical Journal Supplement Series, 1998
- Theoretical Models for Asteroseismology of DA White Dwarf StarsThe Astrophysical Journal, 1996
- Low-temperature Rosseland opacitiesThe Astrophysical Journal, 1994
- Abundances of the elements: Meteoritic and solarGeochimica et Cosmochimica Acta, 1989
- Acoustic fluxes in white dwarfsThe Astrophysical Journal, 1980
- Carbon-Burning Nucleosynthesis at Constant TemperatureThe Astrophysical Journal, 1969