The Physics and End-Products of Merging CO WD Binaries

TL;DR

This paper reviews current hydrodynamic simulations of merging carbon-oxygen white dwarf binaries, emphasizing the role of temperature in their evolution and discussing how magnetic fields generated during mergers may influence supernova ignition.

Contribution

It highlights the importance of temperature over density or mass in merger outcomes and presents recent simulations showing magnetic field generation during white dwarf mergers.

Findings

Temperature most strongly influences merger evolution.

Mergers generate strong magnetic fields.

Magnetic fields may trigger supernova ignition.

Abstract

The merger of two carbon-oxygen white dwarfs has long been theorized to lead to a massive carbon-oxygen or oxygen-neon white dwarf, accretion-induced collapse to a neutron star, or a type Ia supernova. Determining which mergers lead to a particular outcome requires hydrodynamic simulations of the merging process. I give a brief overview of the current understanding of mergers and their end-products derived from simulations, and show how temperature, rather than density or mass, most strongly determines a merging binary's subsequent evolution. I then describe recent simulations that show mergers generate strong magnetic fields that could help drive a merger remnant to ignition.