Department of Physics, University of Florida, P.O. Box 118440, Gainesville, Forida 32611-8440, USA.
Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India.
Phys Rev Lett. 2019 Nov 1;123(18):181101. doi: 10.1103/PhysRevLett.123.181101.
The origins of the stellar-mass black hole mergers discovered by LIGO/Virgo are still unknown. Here we show that if migration traps develop in the accretion disks of active galactic nuclei (AGNs) and promote the mergers of their captive black holes, the majority of black holes within disks will undergo hierarchical mergers-with one of the black holes being the remnant of a previous merger. 40% of AGN-assisted mergers detected by LIGO/Virgo will include a black hole with mass ≳50M_{⊙}, the mass limit from stellar core collapse. Hierarchical mergers at traps in AGNs will exhibit black hole spins (anti)aligned with the binary's orbital axis, a distinct property from other hierarchical channels. Our results suggest, although not definitively (with odds ratio of ∼1), that LIGO's heaviest merger so far, GW170729, could have originated from this channel.
引力波探测器 LIGO/Virgo 探测到的恒星级质量黑洞并合的起源仍然未知。在这里，我们表明，如果活动星系核（AGN）吸积盘中出现迁移陷阱，并促进被俘获黑洞的并合，那么盘中的大多数黑洞将经历等级并合——其中一个黑洞是前一次并合的残余。引力波探测器 LIGO/Virgo 探测到的 AGN 辅助并合中，有 40%将包含质量≳50M⊙的黑洞，这是恒星核心坍缩的质量极限。AGN 中陷阱处的等级并合将表现出黑洞自旋（反）与双星轨道轴对齐的特性，这是与其他等级通道明显不同的特性。我们的结果表明，尽管不是确定无疑的（优势比约为 1），但 LIGO 迄今为止探测到的最重的并合事件 GW170729 可能来自这个通道。
