The Effect of 22NE Diffusion in the Evolution and Pulsational Properties of White Dwarfs with Solar Metallicity Progenitors

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

ASTROPHYSICAL JOURNAL

IOP PUBLISHING LTD

Lugar: Londres; Año: 2016

0004-637X

Because of the large neutron excess of 22Ne, sedimentation ofthis isotope occurs rapidly in the interior of white dwarfs. Thisprocess releases an additional amount of energy, thus delaying thecooling times of the white dwarf. This influences the ages of differentstellar populations derived using white dwarf cosmochronology.Furthermore, the overabundance of 22Ne in the inner regionsof the star modifies the Brunt?Väisälä frequency,thus altering the pulsational properties of these stars. In this work wediscuss the impact of 22Ne sedimentation in white dwarfsresulting from solar metallicity progenitors (Z = 0.02). We performedevolutionary calculations of white dwarfs with masses of 0.528, 0.576,0.657, and 0.833 {M}ȯ derived from full evolutionarycomputations of their progenitor stars, starting at the zero-age mainsequence all the way through the central hydrogen and helium burning,the thermally pulsing asymptotic giant branch (AGB), and post-AGBphases. Our computations show that at low luminosities({log}(L/{L}ȯ )≲ -4.25), 22Nesedimentation delays the cooling of white dwarfs with solar metallicityprogenitors by about 1 Gyr. Additionally, we studied the consequences of22Ne sedimentation on the pulsational properties of ZZ Cetiwhite dwarfs. We find that 22Ne sedimentation inducesdifferences in the periods of these stars larger than the presentobservational uncertainties, particularly in more massive white dwarfs.