Crystallization of carbon-oxygen mixtures in white dwarf stars

C. J. Horowitz, A. S. Schneider, D. K. Berry

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Abstract

We determine the phase diagram for dense carbon-oxygen mixtures in white dwarf (WD) star interiors using molecular dynamics simulations involving liquid and solid phases. Our phase diagram agrees well with predictions from Ogata et al. and from Medin and Cumming and gives lower melting temperatures than Segretain et al. Observations of WD crystallization in the globular cluster NGC 6397 by Winget et al. suggest that the melting temperature of WD cores is close to that for pure carbon. If this is true, our phase diagram implies that the central oxygen abundance in these stars is less than about 60%. This constraint, along with assumptions about convection in stellar evolution models, limits the effective S factor for the C12(α,γ)O16 reaction to S300≤170keVb.

Original languageEnglish
Article number231101
JournalPhysical Review Letters
Volume104
Issue number23
DOIs
StatePublished - 7 Jun 2010
Externally publishedYes

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