Evolution of a 3 \msun star from the main sequence to the ZZ Ceti stage: the role played by element diffusion

摘要

The purpose of this paper is to present new full evolutionary calculationsfor DA white dwarf stars with the major aim of providing a physically soundreference frame for exploring the pulsation properties of the resulting modelsin future communications. Here, white dwarf evolution is followed in aself-consistent way with the predictions of time dependent element diffusionand nuclear burning. In addition, full account is taken of the evolutionarystages prior to the white dwarf formation. In particular, we follow theevolution of a 3 \msun model from the zero-age main sequence (the adoptedmetallicity is Z=0.02) all the way from the stages of hydrogen and heliumburning in the core up to the thermally pulsing phase. After experiencing 11thermal pulses, the model is forced to evolve towards its white dwarfconfiguration by invoking strong mass loss episodes. Further evolution isfollowed down to the domain of the ZZ Ceti stars on the white dwarf coolingbranch. Emphasis is placed on the evolution of the chemical abundancedistribution due to diffusion processes and the role played by hydrogen burningduring the white dwarf evolution. Furthermore, the implications of ourevolutionary models for the main quantities relevant for adiabatic pulsationanalysis are discussed. Interestingly, the shape of the Ledoux term is markedlysmoother as compared with previous detailed studies of white dwarfs. This istranslated into a different behaviour of the Brunt-Vaisala frequency.