Skye: A Differentiable Equation of State

Jermyn, Adam S.; Schwab, Josiah; Bauer, Evan B.; Timmes, F. X.; Potekhin, A. Y.

doi:10.3847/1538-4357/abf48e

Cited by 71 publications

(56 citation statements)

References 92 publications

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“…We have therefore modified the fit of Paper III to improve the agreement with the new data in the liquid. [In addition, it has been noticed by Jermyn et al (2021) that the fit of Paper III demonstrated unphysical behaviour in the practically unattainable region of very high densities, rs 300. This behaviour is also corrected by the present fit modification.…”

Section: Liquid Phase Thermodynamics Updatementioning

confidence: 93%

$Ab~initio$ thermodynamics of one-component plasma for astrophysics of white dwarfs and neutron stars

Baiko,

Chugunov

2021

Preprint

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Using path-integral Monte Carlo (PIMC) simulations, we have calculated energy of a crystal composed of atomic nuclei and uniform incompressible electron background in the temperature and density range, covering fully ionized layers of compact stellar objects, white dwarfs and neutron stars, including the high-density regime, where ion quantization is important. We have approximated the results by convenient analytic formulae, which allowed us to integrate and differentiate the energy with respect to temperature and density to obtain various thermodynamic functions such as Helmholtz free energy, specific heat, pressure, entropy etc. In particular, we have demonstrated, that the total crystal specific heat can exceed the well-known harmonic lattice contribution by a factor of 1.5 due to anharmonic effects. By combining our results with the PIMC thermodynamics of a quantum Coulomb liquid, updated in the present work, we were able to determine density dependences of such melting parameters as the Coulomb coupling strength at melting, latent heat, and a specific heat jump. Our results are necessary for realistic modelling of thermal evolution of compact degenerate stars.

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Section: Liquid Phase Thermodynamics Updatementioning

confidence: 93%

$Ab~initio$ thermodynamics of one-component plasma for astrophysics of white dwarfs and neutron stars

Baiko,

Chugunov

2021

Preprint

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“…The main source of energy during the fluid phase is the gravothermal one. Since the plasma is not very strongly coupled (Γ < 179), its properties are reasonably well known (Segretain et al, 1994;Potekhin and Chabrier, 2010;Jermyn et al, 2021). Furthermore, the flux of energy through the envelope is controlled by a thick non-degenerate layer with an opacity dominated by hydrogen (if present) and helium, and weakly dependent on the metal content.…”

Section: The Evolution Of Single White Dwarfsmentioning

confidence: 99%

White Dwarfs as Physics Laboratories: Lights and Shadows

Isern

Torres

Rebassa‐Mansergas

2022

Front. Astron. Space Sci.

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The evolution of white dwarfs is essentially a gravothermal process of cooling in which the basic ingredients for predicting their evolution are well identified, although not always well understood. There are two independent ways to test the cooling rate. One is the luminosity function of the white dwarf population, and another is the secular drift of the period of pulsation of those individuals that experience variations. Both scenarios are sensitive to the cooling or heating time scales, for which reason, the inclusion of any additional source or sink of energy will modify these properties and will allow to set bounds to these perturbations. These studies also require complete and statistical significant samples for which current large data surveys are providing an unprecedented wealth of information. In this paper we review how these techniques are applied to several cases like the secular drift of the Newton gravitational constant, neutrino magnetic moments, axions and weakly interacting massive particles (WIMPS).

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“…1 we plot the relevant length scales for a crystallizing 0.6 M white dwarf, calculated using the stellar evolution code (Paxton et al 2011(Paxton et al , 2013(Paxton et al , 2015(Paxton et al , 2018(Paxton et al , 2019. Crystallization is assumed to occur when the plasma coupling parameter (the ratio of the Coulomb to thermal energy) exceeds Γ = 230, consistent with the updated 'Skye' equation of state, and appropriate for a CO mixture (Bauer et al 2020;Jermyn et al 2021). This value is somewhat higher than the traditional one-component Γ = 175 (Potekhin & Chabrier 2000, 2010, resulting in lower crystallization temperatures.…”

Section: Typical Valuesmentioning

confidence: 99%

Slow convection and fast rotation in crystallization-driven white dwarf dynamos

Ginzburg,

Fuller,

Kawka

et al. 2022

Preprint

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It has been recently suggested that white dwarfs generate magnetic fields in a process analogous to the Earth. The crystallization of the core creates a compositional inversion that drives convection, and combined with rotation, this can sustain a magnetic dynamo. We reanalyse the dynamo mechanism, arising from the slow crystallization of the core, and find convective turnover times 𝑡 conv of weeks to months -longer by orders of magnitude than previously thought. With white dwarf spin periods 𝑃 𝑡 conv , crystallization-driven dynamos are almost always in the fast rotating regime, where the magnetic field 𝐵 is at least in equipartition with the convective motion and is possibly further enhanced by a factor of 𝐵 ∝ (𝑡 conv /𝑃) 1/2 , depending on the assumed dynamo scaling law. We track the growth of the crystallized core using and compute the magnetic field 𝐵(𝑇 eff ) as a function of the white dwarf's effective temperature 𝑇 eff . We compare this prediction with observations and show that crystallization-driven dynamos can explain some -but not all -of the ∼MG magnetic fields measured for single white dwarfs, as well as the stronger fields measured for white dwarfs in cataclysmic variables, which were spun up by mass accretion to short 𝑃. Our 𝐵(𝑇 eff ) curves might also explain the clustering of white dwarfs with Balmer emission lines around 𝑇 eff ≈ 7500 K.

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Skye: A Differentiable Equation of State

Cited by 71 publications

References 92 publications

$Ab~initio$ thermodynamics of one-component plasma for astrophysics of white dwarfs and neutron stars

$Ab~initio$ thermodynamics of one-component plasma for astrophysics of white dwarfs and neutron stars

White Dwarfs as Physics Laboratories: Lights and Shadows

Slow convection and fast rotation in crystallization-driven white dwarf dynamos

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