Diffusion of Neon in White Dwarf Stars

Abstract

Sedimentation of the neutron rich isotope ${}^{22}$Ne may be an important source of gravitational energy during the cooling of white dwarf stars. This depends on the diffusion constant for ${}^{22}$Ne in strongly coupled plasma mixtures. We calculate self-diffusion constants $D_i$ from molecular dynamics simulations of carbon, oxygen, and neon mixtures. We find that $D_i$ in a mixture does not differ greatly from earlier one component plasma results. For strong coupling (coulomb parameter $\Gamma >$ few), $D_i$ has a modest dependence on the charge $Z_i$ of the ion species, $D_i\propto Z_i^{-2/3}$. However $D_i$ depends more strongly on $Z_i$ for weak coupling (smaller $\Gamma$). We conclude that the self-diffusion constant $D_{\mathrm{Ne}}$ for ${}^{22}$Ne in carbon, oxygen, and neon plasma mixtures is accurately known so that uncertainties in $D_{\mathrm{Ne}}$ should be unimportant for simulations of white dwarf cooling.

6 pages, 5 figures, minor changes, Phys. Rev. E in press

References in corpus (12)

• Thermodynamic functions of dense plasmas: analytic approximations for astrophysical applications
• A white dwarf cooling age of 8 Gyr for NGC 6791 from physical separation processes
• Equation of state of fully ionized electron-ion plasmas. II. Extension to relativistic densities and to the solid phase
• The cooling of CO white dwarfs: influence of the internal chemical distribution
• Gravitational Settling of 22Ne in Liquid White Dwarf Interiors
• Crystallization of Carbon Oxygen Mixtures in White Dwarf Stars
• Sedimentation and Type I X-ray Bursts at Low Accretion Rates
• Gravitational Settling of ^{22}Ne in Liquid White Dwarf Interiors--Cooling and Seismological Effects
• The Physics of Crystallization from Globular Cluster White Dwarf Stars in NGC 6397
• Evolution of Massive Stars Up to the End of Central Oxygen Burning
• Gravitational settling of 22Ne and white dwarf evolution
• A deeper understanding of white dwarf interiors

Cited by in corpus (26)

• Modules for Experiments in Stellar Astrophysics (MESA): Time-Dependent Convection, Energy Conservation, Automatic Differentiation, and Infrastructure
• Current challenges in the physics of white dwarf stars
• Diffusion in a strongly coupled magnetized plasma
• The effect of ${}^{22}$Ne diffusion in the evolution and pulsational properties of white dwarfs with solar metallicity progenitors
• Multi-Gigayear White Dwarf Cooling Delays from Clustering-Enhanced Gravitational Sedimentation
• The updated BaSTI stellar evolution models and isochrones. III. White Dwarfs
• The formation of ultra-massive carbon-oxygen core white dwarfs and their evolutionary and pulsational properties
• Forever young white dwarfs: when stellar ageing stops
• Neon Cluster Formation and Phase Separation During White Dwarf Cooling
• Carbon-Oxygen Phase Separation in MESA White Dwarf Models
• Diffusion and Coulomb separation of ions in dense matter
• Compositionally-driven convection in the oceans of accreting neutron stars
• Diffusion in Coulomb Crystals
• Effective Potential Theory for Diffusion in Binary Ionic Mixtures
• Nuclear and dark matter heating in massive white dwarf stars
• The evolution of ultra-massive carbon oxygen white dwarfs
• Accurate Diffusion Coefficients for Dense White Dwarf Plasma Mixtures
• Effective Potential and Interdiffusion in Binary Ionic Mixtures
• The effects of ${}^{22}$Ne sedimentation and metallicity on the local 40 pc white dwarf luminosity function
• Actinide crystallization and fission reactions in cooling white dwarf stars
• Cooling Models for the Most Massive White Dwarfs
• Direct MD simulation of liquid-solid phase equilibria for two-component plasmas
• Precise Diffusion Coefficients for White Dwarf Astrophysics
• A Crystallizing White Dwarf in a Sirius-Like Quadruple System
• On excess entropy and latent heat in crystallizing white dwarfs
• Chemical element transport in stellar evolution models