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arXiv 1606.07097astro-ph.HEgr-qc
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球状星团中等质量比吸气的$N-$体动力学

$N-$body dynamics of Intermediate mass-ratio inspirals in globular clusters

Carl-Johan Haster, Fabio Antonini, Vicky Kalogera, Ilya Mandel

摘要:

恒星致密残骸进入中等质量黑洞(IMBH)的中等质量比螺旋可以产生引力波(GW)信号,该信号可能被当前的地面GW探测器(例如,先进的LIGO)以及计划中的天基干涉仪(例如,eLISA)。在这里,我们提出了直接整合的后牛顿$N$ -体运动方程描述星团包含一个IMBH和人口的恒星质量黑洞(BH)和太阳质量的恒星。我们特别注意模拟最接近IMBH的动力学,包括后牛顿效应达到$2.5$阶。我们的模拟结果表明,IMBH很容易形成一个与BH同伴的二进制文件。这颗双星在短暂的三体或四体碰撞中逐渐变硬,导致BH伴星的频繁替换,而由于Lidov-Kozai共振,双星的偏心率经历了大幅度的振荡。我们还证明了抑制这些共振的相对论进动的二元轨道。在我们为$\sim 100$ Myr演化的12个星系团模型中,我们发现了一个中等质量比的螺旋形。这个星团拥有一个$100 M_\odot$ IMBH,它嵌入在32颗$10M_\odot$ BH和32,000颗$1M_\odot$恒星中。在模拟的最后,经过$\sim 100$ Myr的进化,IMBH与BH伴星合并。IMBH-BH双星在达到偏心率$1-e\simeq 10^{-3}$时,在eLISA频率窗口($\gtrsim 1\rm mHz$)中开始螺旋上升。经过$\simeq 10^5$年后,双星进入LIGO频段,偏心率可以忽略不计。我们评论GW搜索的影响,在未来十年内可能会检测到。

英文摘要:

The intermediate mass-ratio inspiral of a stellar compact remnant into an intermediate mass black hole (IMBH) can produce a gravitational wave (GW) signal that is potentially detectable by current ground-based GW detectors (e.g., Advanced LIGO) as well as by planned space-based interferometers (e.g., eLISA). Here, we present results from a direct integration of the post-Newtonian $N$-body equations of motion describing stellar clusters containing an IMBH and a population of stellar-mass black holes (BHs) and solar mass stars. We take particular care to simulate the dynamics closest to the IMBH, including post-Newtonian effects up to order $2.5$. Our simulations show that the IMBH readily forms a binary with a BH companion. This binary is gradually hardened by transient 3-body or 4-body encounters, leading to frequent substitutions of the BH companion, while the binary's eccentricity experiences large amplitude oscillations due to the Lidov-Kozai resonance. We also demonstrate suppression of these resonances by the relativistic precession of the binary orbit. We find an intermediate mass-ratio inspiral in one of the 12 cluster models we evolved for $\sim 100$ Myr. This cluster hosts a $100 M_\odot$ IMBH embedded in a population of 32 $10M_\odot$ BH and 32,000 $1M_\odot$ stars. At the end of the simulation, after $\sim 100$ Myr of evolution, the IMBH merges with a BH companion. The IMBH--BH binary inspiral starts in the eLISA frequency window ($\gtrsim 1\rm mHz$) when the binary reaches an eccentricity $1-e\simeq 10^{-3}$. After $\simeq 10^5$ years the binary moves into the LIGO frequency band with a negligible eccentricity. We comment on the implications for GW searches, with a possible detection within the next decade.

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