A Parameter-Space Study of Carbon-Oxygen White Dwarf Mergers

Understand

The merger of two carbon-oxygen white dwarfs can lead either to a spectacular transient, stable nuclear burning or a massive, rapidly rotating white dwarf.

• Simulations of mergers have shown that the outcome strongly depends on whether the white dwarfs are similar or dissimilar in mass.
• In the similar-mass case, both white dwarfs merge fully and the remnant is hot throughout, while in the dissimilar case, the more massive, denser white dwarf remains cold and essentially intact, with the disrupted lower mass one wrapped around it in a hot envelope and disk.
• In order to determine what constitutes "similar in mass" and more generally how the properties of the merger remnant depend on the input masses, we simulated unsynchronized carbon-oxygen white dwarf mergers for a large range of masses using smoothed-particle hydrodynamics.