Evolutionary and pulsational properties of ultra-massive white dwarfs. The role of oxygen-neon phase separation

CÓRSICO, ALEJANDRO HUGO; DE GERÓNIMO, FRANCISCO CÉSAR; ALTHAUS, LEANDRO GABRIEL; CAMISASSA, MARÍA

Austin, Texas

Conferencia; 21st European Workshop on White Dwarfs; 2018

The University of Texas at Austin

Ultra-massive hydrogen-rich white dwarfs starsare expected to harbour oxygen/neon cores resultingfrom semidegenerate carbon burning when theprogenitor star evolves through the super asymptoticgiant branch (S-AGB) phase. These stars areexpected to be crystallized by the time they reachthe ZZ Ceti domain. We show that crystallizationleads to a phase separation of oxygen and neon inthe core of ultra-massive white dwarfs, which impactsmarkedly the pulsational properties, thus offeringa unique opportunity to infer and test theprocess of crystallization and phase separation inwhite dwarf stars.