CONICET | Buscador de Institutos y Recursos Humanos

Context. Some globular clusters host multiple stellar populations withdifferent chemical abundance patterns. This is particularly true forω Centauri, which shows clear evidence of a helium-enrichedsubpopulation characterized by a helium abundance as high as Y = 0.4 Aims: We present a whole and consistent set of evolutionary tracksfrom the ZAMS to the white dwarf stage that is appropriate for the studyof the formation and evolution of white dwarfs resulting from theevolution of helium-rich progenitors. Methods: We derived whitedwarf sequences from progenitors with stellar mass ranging from 0.60 to2.0 M⊙ and for an initial helium abundance of Y = 0.4. Weadopted two values of metallicity: Z = 0.001 and Z = 0.0005. Results: We explored different issues of white dwarf evolution and theirhelium-rich progenitors. In particular, the final mass of the remnants,the role of overshooting during the thermally pulsing phase, and thecooling of the resulting white dwarfs differ markedly from theevolutionary predictions of progenitor stars with the standard initialhelium abundance. Finally, the pulsational properties of the resultingwhite dwarfs are also explored. Conclusions: We find that, forthe range of initial masses explored in this paper, the final mass ofthe helium-rich progenitors is markedly higher than the final massexpected from progenitors with the usual helium abundance. We also findthat progenitors with initial mass lower than M ≃ 0.65M⊙ evolve directly into helium-core white dwarfs in lessthan 14 Gyr, and that, for larger progenitor masses, the evolution ofthe resulting low-mass carbon-oxygen white dwarfs is dominated byresidual nuclear burning. For helium-core white dwarfs, we find thatthey evolve markedly faster than their counterparts coming from standardprogenitors. Also, in contrast with what occurs for white dwarfsresulting from progenitors with the standard helium abundance, theimpact of residual burning on the cooling time of white dwarfs is notaffected by the occurrence of overshooting during the thermally pulsingphase of progenitor stars.