TEARING UP THE DISK: HOW BLACK HOLES ACCRETE
TEARING UP THE DISK: HOW BLACK HOLES ACCRETE
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撕碎圆盘：黑洞如何吸积
DOI：
10.1088/2041-8205/757/2/l24
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
J. Frank
中科院分区：
文献类型：
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作者：
C. Nixon;A. King;Daniel J. Price;J. Frank
我们表明，在现实的情况下，在活动星系核或恒星质量的X射线双星吸积，Lense-Thirring效应打破了旋转黑洞周围的倾斜吸积盘的中心区域成一组不同的平面，只有纤细的流动连接它们。如果外盘与黑洞自转轴的初始偏差为45° <$θ <$135 °，就像70%的随机吸积事件一样，这些盘的持续进动会产生部分反向旋转的气流。当角动量被抵消，气体试图在更小的半径处形成圆形时，这就驱动了快速的坍缩。靠近黑洞的圆盘破裂导致直接的动力吸积，而进一步破裂可以将气体驱动到可以快速吸积的尺度。对于较小的倾斜角，断裂仍然可以发生，并且可能导致其他可观察到的现象，例如准周期振荡。要想不出现这种效应，黑洞的自旋实际上必须小到可以忽略不计，或者几乎精确地与圆盘对齐。类似的结果适用于任何受强迫微分进动的吸积盘，例如围绕未对准黑洞双星的外部盘。
We show that in realistic cases of accretion in active galactic nuclei or stellar-mass X-ray binaries, the Lense–Thirring effect breaks the central regions of tilted accretion disks around spinning black holes into a set of distinct planes with only tenuous flows connecting them. If the original misalignment of the outer disk to the spin axis of the hole is 45° ≲ θ ≲ 135°, as in ∼70% of randomly oriented accretion events, the continued precession of these disks sets up partially counterrotating gas flows. This drives rapid infall as angular momentum is canceled and gas attempts to circularize at smaller radii. Disk breaking close to the black hole leads to direct dynamical accretion, while breaking further out can drive gas down to scales where it can accrete rapidly. For smaller tilt angles breaking can still occur and may lead to other observable phenomena such as quasi-periodic oscillations. For such effects not to appear, the black hole spin must in practice be negligibly small, or be almost precisely aligned with the disk. Qualitatively similar results hold for any accretion disk subject to a forced differential precession, such as an external disk around a misaligned black hole binary.