Nuclear-dominated accretion and subluminous supernovae from the merger of a white dwarf with a neutron star or black hole
Nuclear-dominated accretion and subluminous supernovae from the merger of a white dwarf with a neutron star or black hole
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DOI：
10.1111/j.1365-2966.2011.19747.x
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发表时间：
2011-05
影响因子：
4.8
通讯作者：
B. Metzger
中科院分区：
文献类型：
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作者：
B. Metzger
本文建立了中子星星（NS）或恒星质量黑洞（BH）对白色矮星（WD）的潮汐破坏所产生的吸积盘的一维稳态模型。在半径r = 10 8.5 - 10 9 cm处，中平面的密度和温度足够高，足以将最初的白色矮星材料燃烧成半径依次变小的越来越重的元素（例如Mg、Si、S、Ca、Fe和Ni）。当核反应释放的能量与引力释放的能量相当时，我们称之为核主导的吸积流（Nuclear-dominated accretion flow）。在小半径的107厘米铁光分解成氦，然后自由核，并在最里面的磁盘冷却中微子可能是有效的。在相关的高吸积率为10 −4 − 0.1 M s −1时，盘的大部分是辐射无效的，并且容易由粘性耗散和核燃烧提供动力的外流。流出特性的计算要求中平面的材料是边缘约束的（伯努利常数<0），这（部分）是由于物质逸出圆盘而冷却。对于盘风性质的合理假设，我们证明了WD总质量的很大一部分（约50 - 80%）是未束缚的。喷出物的成分主要是O、C、Si、Mg、Ne、Fe和S [He、C、Si、S、Ar和Fe]，在C-O [纯He] WD的情况下，分别是沿着少量的放射性56 Ni和可能的痕量氢。根据风冷却的压力依赖性，我们发现，磁盘可能是热不稳定的核燃烧，其可能性增加了更高的质量WD。我们使用我们的结果来评估可能的电磁对应的WD NS/BH合并，包括光学瞬态供电的放射性衰变的56 Ni和无线电瞬态供电的喷出物与星际介质的相互作用。我们解决最近发现的亚发光I型超新星是否来自WD-NS/BH合并。最终评估这些事件的命运需要对磁盘演化进行全球模拟，以捕捉核燃烧，对流和外流之间的复杂相互作用。
We construct one dimensional steady-state models of accretion disks produced by the tidal disruption of a white dwarf (WD) by a neutron star (NS) or stellar mass black hole (BH). At radii r ∼ 10 8.5 − 10 9 cm the midplane density and temperature are suffi ciently high to burn the initial white dwarf material into increasingly heavier elements (e.g. Mg, Si, S, Ca, Fe, and Ni) at sequentially smaller radii. When the energy relea sed by nuclear reactions is comparable to that released gravitationally, we term the disk a nuclear-dominated accretion flow (NuDAF). At small radii ∼ 10 7 cm iron photo-disintegrates into helium and then free nuclei, and in the very innermost disk cooling by neutrinos may be effi cient. At the high accretion rates of relevance∼ 10 −4 − 0.1M⊙ s −1 , most of the disk is radiatively ineffi cient and prone to outflows powered by viscous dissipation and nuclear burning . Outflow properties are calculated by requiring that material in the midplane be marginal ly bound (Bernoulli constant ∼ 0), due (in part) to cooling by matter escaping the disk. For reas onable assumptions regarding the properties of disk winds, we show that a significant fraction ( ∼ 50− 80%) of the total WD mass is unbound. The composition of the ejecta is predominantly O, C, Si, Mg, Ne, Fe, and S [He, C, Si, S, Ar, and Fe], in the case of C-O [pure He] WDs, respectively, along with a small quantity∼ 10 −3 − 10 −2 M⊙ of radioactive 56 Ni and, potentially, a trace amount of hydrogen. Depending on the pressure dependence of wind cooling, we find that the disk may be thermally unstable to nuclear burning, the likelihood of which increases for higher mass WDs. We use our results to evaluate possible electromagnetic counterparts of WD-NS/BH mergers, including optical transients powered by the radioacti ve decay of 56 Ni and radio transients powered by the interaction of the ejecta with the interstell ar medium. We address whether recently discovered subluminous Type I supernovae result from WD-NS/BH mergers. Ultimately assessing the fate of these events requires global si mulations of the disk evolution, which capture the complex interplay between nuclear burning, convection, and outflows.