The Physics of Crystallization from Globular Cluster White Dwarf Stars in NGC 6397

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Date

2009-03

Authors

Winget, D. E.
Kepler, S. O.
Campos, Fabiola
Montgomery, M. H.
Girardi, Leo
Bergeron, P.
Williams, Kurtis

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Abstract

We explore the physics of crystallization in the deep interiors of white dwarf (WD) stars using the color-magnitude diagram and luminosity function constructed from proper- motion cleaned Hubble Space Telescope photometry of the globular cluster NGC 6397. We demonstrate that the data are consistent with the theory of crystallization of the ions in the interior of WD stars and provide the first empirical evidence that the phase transition is first order: latent heat is released in the process of crystallization as predicted by van Horn. We outline how these data can be used to observationally constrain the value of Gamma = E(Coulomb)/E(thermal) near the onset of crystallization, the central carbon/oxygen abundance, and the importance of phase separation.

Department

Astronomy

Description

Keywords

dense matter, equation of state, globular clusters: individual (ngc, 6397), stars: luminosity function, mass function, white dwarfs, monte-carlo calculations, cooling sequence, luminosity function, giant, branch, ngc-6397, asteroseismology, evolution, plasma, mixtures, equation, astronomy & astrophysics

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Citation

Winget, Donald Earl, Souza Oliveira Kepler, Fabíola Campos, Michael Houston Montgomery, Leo Girardi, Pierre Bergeron, and Kurtis Williams. "The physics of crystallization from globular cluster white dwarf stars in NGC 6397." The Astrophysical Journal Letters, Vol. 693, No. 1 (Mar., 2009): L6.

URI

http://hdl.handle.net/2152/42970

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