Merged white dwarfs and nucleosynthesis

TL;DR

This paper discusses the inevitability of double white dwarf mergers, their outcomes including explosions and survivors, and how spectroscopic surveys can reveal their nucleosynthesis history.

Contribution

It highlights the nuclear processes during white dwarf mergers and identifies potential observable survivors through spectroscopic surveys.

Findings

Survivors include extreme helium stars and R CrB variables.

Surface nuclear waste reveals pre-merger and merger nucleosynthesis.

Spectroscopic surveys can uncover new merger remnants.

Abstract

Orbital decay mechanisms argue that double white dwarf mergers are inevitable, but extremely rare. Whilst some mergers result in explosions, the survivors re-ignite helium and burn brightly for tens of thousands or millions of years. Candidate survivors include extreme helium stars, R CrB variables and various classes of helium-rich subluminous star. Nuclear waste on the survivors' surfaces provides evidence of the stars' nuclear history prior to and their nucleosynthesis during the merger. Extensive and deep spectroscopic surveys offer rich prospects for future discoveries.