Remnants of Binary White Dwarf Mergers

TL;DR

This study uses hydrodynamic simulations to analyze the remnants of binary white dwarf mergers, revealing common structural features and conditions leading to helium detonations without subsequent carbon ignition.

Contribution

It provides a detailed characterization of merger remnants and explores the conditions for helium detonations, advancing understanding of white dwarf merger outcomes.

Findings

Most remnants have a degenerate core with a hot disk

Some massive mergers exhibit helium detonations

Helium detonations do not trigger carbon ignition

Abstract

We carry out a comprehensive smooth particle hydrodynamics simulation survey of double-degenerate white dwarf binary mergers of varying mass combinations in order to establish correspondence between initial conditions and remnant configurations. We find that all but one of our simulation remnants share general properties such as a cold, degenerate core surrounded by a hot disk, while our least massive pair of stars forms only a hot disk. We characterize our remnant configurations by the core mass, the rotational velocity of the core, and the half-mass radius of the disk. We also find that some of our simulations with very massive constituent stars exhibit helium detonations on the surface of the primary star before complete disruption of the secondary. However, these helium detonations are insufficiently energetic to ignite carbon, and so do not lead to prompt carbon detonations.