The Impact of Vector Resonant Relaxation on the Evolution of Binaries near a Massive Black Hole: Implications for Gravitational-wave Sources
The Impact of Vector Resonant Relaxation on the Evolution of Binaries near a Massive Black Hole: Implications for Gravitational-wave Sources
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DOI：
10.3847/1538-4357/aadae2
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发表时间：
2018-05
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影响因子：
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通讯作者：
A. Hamers;Ben Bar-Or;C. Petrovich;F. Antonini
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文献类型：
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作者：
A. Hamers;Ben Bar-Or;C. Petrovich;F. Antonini
星系核中大质量黑洞(MBH)影响范围内的双星容易受到Lidov-Kozai(LK)机制的影响，该机制可以将轨道驱动到高偏心率，并在双星内部引发强烈的相互作用，如引力波(GWS)的发射和致密天体的合并。这些事件是高级LIGO和处女座等GW探测器的潜在来源。LK机制只有在双星相对于其围绕MBH的轨道高度倾斜(在90°范围内)时才有效，这意味着低速率。然而，在MBH附近，来自星团的力矩引起矢量共振弛豫(VRR)过程。VRR可以将低倾角双星带入“活跃的”LK区域，在该区域中，高偏心率和强相互作用被触发。在这里，我们研究了LK-VRR耦合动力学，对LIGO和室女座GW源具有重要意义。我们进行了蒙特卡罗模拟，发现在假设的∼质量()的下端，由LK-VRR动力学引起的合并分数增加可达10倍，并且随着M·的增加而急剧减小。我们发现，即使在我们最乐观的情况下，基线的BH-BH合并率也很小，LK-VRR耦合的增强也不足以将合并率增加到远高于LIGO/Virgo下限。对于银河中心，LK-VRR的增强率是LIGO/处女座极限的∼100倍，而对于银河系中心，这一比率仅勉强达到。
Binaries within the sphere of influence of a massive black hole (MBH) in galactic nuclei are susceptible to the Lidov–Kozai (LK) mechanism, which can drive orbits to high eccentricities and trigger strong interactions within the binary such as the emission of gravitational waves (GWs) and mergers of compact objects. These events are potential sources for GW detectors such as Advanced LIGO and VIRGO. The LK mechanism is only effective if the binary is highly inclined with respect to its orbit around the MBH (within a few degrees of 90°), implying low rates. However, close to an MBH, torques from the stellar cluster give rise to the process of vector resonant relaxation (VRR). VRR can bring a low-inclination binary into an “active” LK regime in which high eccentricities and strong interactions are triggered in the binary. Here, we study the coupled LK–VRR dynamics, with implications for LIGO and VIRGO GW sources. We carry out Monte Carlo simulations and find that the merger fraction enhancement due to LK–VRR dynamics is up to a factor of ∼10 for the lower end of assumed MBH masses ( ) and decreases sharply with increasing M•. We find that, even in our most optimistic scenario, the baseline BH–BH merger rate is small, and the enhancement by LK–VRR coupling is not large enough to increase the rate to well above the LIGO/VIRGO lower limit, . For the Galactic Center, the LK–VRR-enhanced rate is ∼100 times lower than the LIGO/VIRGO limit, and for , the rate barely reaches .