# Rotating white dwarf models with finite-temperature envelope

## TL;DR

This paper introduces a numerical method for modeling differentially rotating white dwarfs with thermal stratification, revealing how hot envelopes and rotation profiles influence their mass and stability, relevant for understanding white dwarf merger remnants.

## Contribution

The paper develops a new numerical approach to model rotating white dwarfs with thermal envelopes, highlighting the impact of differential rotation and envelope composition on their mass and evolution.

## Key findings

- Differential rotation can double the white dwarf mass beyond the Chandrasekhar limit.
- Hot envelopes slightly increase mass in uniform rotation but have a significant effect in differential rotation.
- Existence of equilibrium sequences depends on rotation profile, entropy, and composition.

## Abstract

We present new numerical method to compute structures of differentially rotating white dwarfs with thermal stratification. Our models have cores composed of ions and completely degenerate electrons and have isentropic envelopes composed of ions, photons, partially degenerate electrons and positrons. The models are intended to mimic very early phases of remnants of white dwarf binary mergers, some of which may lead to type Ia supernovae. The effect of hot envelope to increase the mass depends on its chemical composition through the mean molecular weight of the envelope. For uniformly rotating models, we see only a small increase in mass even in the presence of hot envelope. Differential rotation changes it drastically and super-Chandrasekhar mass model whose mass doubles the Chandrasekhar mass of the degenerate star for some parameter choices. We also compute quasi-equilibrium evolutionary sequences of remnants by fixing either total angular momentum or entropy in the envelope. Existence of these sequences depends on various factors such as the remnant mass, the profile of differential rotation, the entropy and the chemical composition of the envelope.