Merging White Dwarfs, Thermonuclear Supernovae, Other Transients

合并白矮星、热核超新星和其他瞬态现象两颗白矮星的合并会导致壮观的瞬态现象——一颗热核超新星或吸积引起的坍缩成一颗中子星——或者形成奇怪的物体——比如R CrB氦巨星。我们最近意识到，两颗由碳和氧组成的白矮星的合并很可能产生大多数热核超新星，而这与目前的范式相反，很可能与它们的总质量是否超过最大可能的钱德拉塞卡质量无关。我的建议是发展这个新的研究方向，希望能回答以下一系列问题：是什么触发了热核超新星？从观测来看，我们能区分出是近钱德拉塞卡天体的高密度还是次钱德拉塞卡天体的高温引起的点火吗？它是发生在与另一颗白矮星的快速合并中，还是发生在伴星的缓慢吸积中？白矮星合并的结果是什么？通过模拟，合并残留物有什么特性？当剩余的磁盘吸积和自旋演化时会发生什么？是否有人会引发核逃逸？接下来会发生爆炸吗？这会产生热核超新星吗？还有什么其他的瞬变现象？自然界中有什么类型的瞬变？理论预测的大量不同的瞬变是否真的发生了？有我们没有想象到的吗？对于超新星，我们能看到恒星爆发的冲击波吗？看到抛射物与伴星、磁盘或其环境的相互作用吗？

MERGING WHITE DWARFS, THERMONUCLEAR SUPERNOVAE, AND OTHER TRANSIENTSThe merger of two white dwarfs can lead to a spectacular transient -- a thermonuclear supernova or accretion induced collapse to a neutron star -- or the formation of strange objects -- such as the R CrB helium giant stars. We recently realized that mergers of two white dwarfs made of carbon and oxygen might well produce most thermonuclear supernovae, and that this would, contrary to the current paradigm, likely happen independently of whether or not their total mass exceeds the maximum possible, Chandrasekhar mass. My proposal is to develop this new research direction, hoping to answer the following sets of questions:What triggers thermonuclear supernovae? From observations, can we distinguish ignition due to high density in a near-Chandrasekhar object, or due to high temperature in a sub-Chandrasekhar one? Does it happen in a fast merger with another white dwarf, or during slow accretion from a companion?What are the outcomes of white-dwarf mergers? Using simulations, what properties do merger remnants have? What happens as remaining disks accrete and spins evolve? Will some ignite nuclear runaways? Might detonations follow? Would this produce thermonuclear supernovae? What other transients might one expect?What types of transients occur in Nature? Do the multitudes of different transients predicted by theory actually occur? Are there ones we failed to imagine? For supernovae, can we see the shock break out of the star? See ejecta interact with a companion, a disk, or its environment?