The updated BaSTI stellar evolution models and isochrones. III. White Dwarfs

Abstract

We present new cooling models for carbon-oxygen white dwarfs with both H-and He-atmospheres, covering the whole relevant mass range, to extend our updated BaSTI (a Bag of Stellar Tracks and Isochrones) stellar evolution archive. They have been computed using core chemical stratifications obtained from new progenitor calculations, adopting a semiempirical initial-final mass relation. The physics inputs have been updated compared to our previous BaSTI calculations: 22 Ne diffusion in the core is now included, together with an updated CO phase diagram, and updated electron conduction opacities. We have calculated models with various different neon abundances in the core, suitable to study white dwarfs in populations with metallicities ranging from super-solar to metal poor, and have performed various tests/comparisons of the chemical stratification and cooling times of our models. Two complete sets of calculations are provided, for two different choices of the electron conduction opacities, to reflect the current uncertainty in the evaluation of the electron thermal conductivity in the transition regime between moderate and strong degeneracy, crucial for the H and He envelopes. We have also made a first, preliminary estimate of the effect -that turns out to be generally small -of Fe sedimentation on the cooling times of white dwarf models, following recent calculations of the phase diagrams of carbon-oxygen-iron mixtures. We make publicly available the evolutionary tracks from both sets of calculations, including cooling times and magnitudes in the Johnson-Cousins, Sloan, Pan-STARSS, Galex, Gaia-DR2, Gaia-eDR3, HST -ACS, HST -WFC3, and JW ST photometric systems.

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

“…This approach seems to be still applied as microphysics input in WD cooling theory (e.g. Segretain et al, 1994;Salaris et al, 2021), even though it completely ignores the ion quantum effects for the anharmonic term. These effects were not considered by Stringfellow et al (1990), whose work was based on purely classic Monte Carlo.…”