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arXiv 2201.08399astro-ph.HEgr-qc
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合并大质量黑洞双星的恒星轨道演化

Evolution of Stellar Orbits Around Merging Massive Black-Hole Binary

Bin Liu, Dong Lai

摘要:

考虑黑洞自旋引起的广义相对论效应,研究了大质量或超大质量黑洞(BH)并合双星周围恒星的长期轨道演化。当BH自旋与双星轨道角动量相比很重要且不重合时,环双星的轨道轴($\hat{\mathbf{l}}$)在引力辐射驱动的双星轨道衰变过程中会经历显著的演化。考虑到BH的自旋效应,我们发现从近共面的轨道取向开始,无论BH双星的初始自旋取向如何,环联星的轨道轴$\hat{\mathbf{l}}$都优先向BH双星合并后的自旋方向演化.这种对准现象,即,在$\hat{\mathbf{l}}$和反射BH $\hat{\mathbf{S}}$的自旋轴之间的小的最终失准角,可以使用绝热不变性原理来分析地理解。对于具有极端质量比($m_2/m_1\lesssim0.01$)的BH双星,由于绝热不变性的破坏,$\hat{\mathbf{l}}$可能经历更复杂的演化,但是当初始双星的自旋轨道角相对较小时,排列的趋势仍然相当好。我们的结果表明,恒星轨道的取向和中心BH的自旋轴之间的相关性可以提供一个潜在的签名的合并历史的大质量BH。

英文摘要:

We study the long-term orbital evolution of stars around a merging massive or supermassive black-hole (BH) binary, taking into account the general relativistic effect induced by the BH spin. When the BH spin is significant compared to and misaligned with the binary orbital angular momentum, the orbital axis ($\hat{\mathbf{l}}$) of the circumbinary star can undergo significant evolution during the binary orbital decay driven by gravitational radiation. Including the spin effect of the primary (more massive) BH, we find that starting from nearly coplanar orbital orientations, the orbital axes $\hat{\mathbf{l}}$ of circumbinary stars preferentially evolve towards the spin direction after the merger of the BH binary, regardless of the initial BH spin orientation. Such alignment phenomenon, i.e., small final misalignment angle between $\hat{\mathbf{l}}$ and the spin axis of the remanent BH $\hat{\mathbf{S}}$, can be understood analytically using the principle of adiabatic invariance. For the BH binaries with extremely mass ratio ($m_2/m_1\lesssim0.01$), $\hat{\mathbf{l}}$ may experience more complicated evolution as adiabatic invariance breaks down, but the trend of alignment still works reasonably well when the initial binary spin-orbit angle is relatively small. Our result suggests that the correlation between the orientations of stellar orbits and the spin axis of the central BH could provide a potential signature of the merger history of the massive BH.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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