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.

中文翻译：

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合并的白矮星和核合成

轨道衰变机制认为双白矮星合并是不可避免的，但极为罕见。虽然一些合并会导致爆炸，但幸存者会重新点燃氦气并明亮地燃烧数万年或数百万年。候选幸存者包括极端氦星、R CrB 变星和各类富氦亚光亮星。幸存者表面的核废料提供了恒星在合并之前的核历史和它们在合并期间的核合成的证据。广泛而深入的光谱调查为未来的发现提供了丰富的前景。