The effect of 22Ne diffusion in the evolution and pulsational properties of White Dwarfs with Solar Metallicity

CAMISASSA, M. E.; ALTHAUS, L. G.; CÓRSICO, A. H.; A. M. SERENELLI; ISERN, J.; MILLER BERTOLAMI, M. M.; GARCIA-BERRO, E.

ASTROPHYSICAL JOURNAL

IOP PUBLISHING LTD

Lugar: Londres; Año: 2016

0004-637X

Because of the large neutron excess of 22Ne, this isotope rapidlysediments in the interior of the white dwarfs. This process releases anadditional amount of energy, thus delaying the cooling times of the whitedwarf. This influences the ages of different stellar populations derived usingwhite dwarf cosmochronology. Furthermore, the overabundance of 22Ne in theinner regions of the star, modifies the Brunt-V"ais"al"a frequency, thusaltering the pulsational properties of these stars. In this work, we discussthe impact of 22Ne sedimentation in white dwarfs resulting from Solarmetallicity progenitors (Z=0.02). We performed evolutionary calculations ofwhite dwarfs of masses 0.528, 0.576, 0.657 and 0.833 M$_{sun}$,derived from full evolutionary computations of their progenitor stars, startingat the Zero Age Main Sequence all the way through central hydrogen and heliumburning, thermally-pulsing AGB and post-AGB phases. Our computations show thatat low luminosities ($log(L/L_{sun})la -4.25$), 22Ne sedimentationdelays the cooling of white dwarfs with Solar metallicity progenitors by about1~Gyr. Additionally, we studied the consequences of 22Ne sedimentation onthe pulsational properties of ZZ~Ceti white dwarfs. We find that 22Nesedimentation induces differences in the periods of these stars larger than thepresent observational uncertainties, particularly in more massive white dwarfs.