Issue |
A&A
Volume 404, Number 2, June III 2003
|
|
---|---|---|
Page(s) | 593 - 609 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20030472 | |
Published online | 02 June 2003 |
New evolutionary models for massive ZZ Ceti stars. I. First results for their pulsational properties
1
Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque S/N, 1900 La Plata, Argentina Instituto de Astrofísica de La Plata, IALP, CONICET e-mail: serenell$\!$,acorsico@fcaglp.unlp.edu.ar$\!$,mikemon@ast.cam.ac.uk
2
Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK
Corresponding author: L. G. Althaus, althaus@fcaglp.fcaglp.unlp.edu.ar
Received:
7
November
2002
Accepted:
24
March
2003
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.
Key words: stars: evolution / stars: abundances / stars: AGB stars: interiors / stars: white dwarfs / stars: oscillations
© ESO, 2003
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