New phase diagrams for dense carbon-oxygen mixtures and white dwarf evolution

Context. Cool white dwarfs are reliable and independent stellar chronometers. The most common white dwarfs have carbon-oxygen dense cores. Consequently, the cooling ages of very cool white dwarfs sensitively depend on the adopted phase diagram of the carbon-oxygen binary mixture. Aims. A new phase d...

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Detalles Bibliográficos
Autores principales: Althaus, Leandro Gabriel, García-Berro, E., Isern, J., Córsico, Alejandro Hugo, Miller Bertolami, Marcelo Miguel
Formato: Articulo
Lenguaje:Inglés
Publicado: 2012
Materias:
Ciencias Astronómicas
stars: evolution
stars: interiors
white dwarfs
Acceso en línea:http://sedici.unlp.edu.ar/handle/10915/84416
Aporte de:
SEDICI (UNLP) de Universidad Nacional de La Plata
id I19-R120-10915-84416
record_format dspace
institution Universidad Nacional de La Plata
institution_str I-19
repository_str R-120
collection SEDICI (UNLP)
language Inglés
topic Ciencias Astronómicas
stars: evolution
stars: interiors
white dwarfs
spellingShingle Ciencias Astronómicas
stars: evolution
stars: interiors
white dwarfs
Althaus, Leandro Gabriel
García-Berro, E.
Isern, J.
Córsico, Alejandro Hugo
Miller Bertolami, Marcelo Miguel
New phase diagrams for dense carbon-oxygen mixtures and white dwarf evolution
topic_facet Ciencias Astronómicas
stars: evolution
stars: interiors
white dwarfs
description Context. Cool white dwarfs are reliable and independent stellar chronometers. The most common white dwarfs have carbon-oxygen dense cores. Consequently, the cooling ages of very cool white dwarfs sensitively depend on the adopted phase diagram of the carbon-oxygen binary mixture. Aims. A new phase diagram of dense carbon-oxygen mixtures appropriate for white dwarf interiors has been recently obtained using direct molecular dynamics simulations. In this paper, we explore the consequences of this phase diagram in the evolution of cool white dwarfs. Methods. To do this we employ a detailed stellar evolutionary code and accurate initial white dwarf configurations, derived from the full evolution of progenitor stars. We use two different phase diagrams, that of Horowitz et al. (2010, Phys. Rev. Lett., 104, 231101), which presents an azeotrope, and the phase diagram of Segretain & Chabrier (1993, A&A, 271, L13), which is of the spindle form. Results. We computed the evolution of 0.593 and 0.878 M ⊙ white dwarf models during the crystallization phase, and we found that the energy released by carbon-oxygen phase separation is smaller when the new phase diagram of Horowitz et al. is used. This translates into time delays that are on average a factor ∼2 smaller than those obtained when the phase diagram of Segretain & Chabrier is employed. Conclusions. Our results have important implications for white dwarf cosmochronology, because the cooling ages of very old white dwarfs are different for the two phase diagrams. This may have a noticeable impact on the age determinations of very old globular clusters, for which the white dwarf color-magnitude diagram provides an independent way of estimating their age.
format Articulo
Articulo
author Althaus, Leandro Gabriel
García-Berro, E.
Isern, J.
Córsico, Alejandro Hugo
Miller Bertolami, Marcelo Miguel
author_facet Althaus, Leandro Gabriel
García-Berro, E.
Isern, J.
Córsico, Alejandro Hugo
Miller Bertolami, Marcelo Miguel
author_sort Althaus, Leandro Gabriel
title New phase diagrams for dense carbon-oxygen mixtures and white dwarf evolution
title_short New phase diagrams for dense carbon-oxygen mixtures and white dwarf evolution
title_full New phase diagrams for dense carbon-oxygen mixtures and white dwarf evolution
title_fullStr New phase diagrams for dense carbon-oxygen mixtures and white dwarf evolution
title_full_unstemmed New phase diagrams for dense carbon-oxygen mixtures and white dwarf evolution
title_sort new phase diagrams for dense carbon-oxygen mixtures and white dwarf evolution
publishDate 2012
url http://sedici.unlp.edu.ar/handle/10915/84416
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