Carbon–Oxygen Phase Separation in Modules for Experiments in Stellar Astrophysics (MESA) White Dwarf Models

Abstract We enhance the treatment of crystallization for models white dwarfs (WDs) in stellar evolution software Modules Experiments Stellar Astrophysics (MESA) by implementing carbon–oxygen (C/O) phase separation. The separation process during leads to transport oxygen toward centers WDs, resulting a more compact structure that liberates gravitational energy as additional heating modestly slows WD cooling timescales. quantify this delay MESA C/O over mass range 0.5–1.0 M ⊙ , finding delays 0.5–0.8 Gyr typical interior profiles. timescales including effect are generally comparable other make similar assumptions about input physics. When considering alongside 22 Ne sedimentation, however, we find both and BaSTI predict modest sedimentation than latest LPCODE models, may therefore require reevaluation previously proposed solutions some anomalies were based on sedimentation. Our implementation open-source provides an important tool building realistic grids well framework expanding our explore physical processes related transitions associated fluid motions interiors.