[论文解读] Stellar dynamics and extreme-mass ratio inspirals

Pau Amaro‐Seoane|arXiv (Cornell University)|May 23, 2012

Astrophysical Phenomena and Observations被引用 7

一句话总结

本文研究了星系中心大质量黑洞（MBH）附近的恒星动力学，重点关注由引力波辐射驱动的极端质量比旋进（EMRIs）。通过模拟恒星向MBH的渐进式旋进及其与MBH的相互作用，该研究使未来毫赫兹引力波任务能够精确测量黑洞的质量和自旋，从而为MBH的生长与吸积机制提供关键见解。

ABSTRACT

Nowadays it is well-established that in the centre of the Milky Way a massive black hole (MBH) with a mass of about four million solar masses is lurking. While there is an emerging consensus about the origin and growth of supermassive black holes (with masses larger than a billion solar masses), MBHs with smaller masses such as the one in our galactic centre remain an understudied enigma. The key to understanding these holes, how some of them grow by orders of magnitude in mass is to understand the dynamics of the stars in the galactic neighborhood. Stars and the central MBH chiefly interact through the gradual inspiral of the stars into the MBH due to the emission of gravitational radiation. Also stars produce gases which will be subsequently accreted by the MBH by collisions and disruptions brought about by the strong central tidal field. Such processes can contribute significantly to the mass of the MBH and progress in understanding them requires theoretical work in preparation for future gravitational radiation millihertz missions and X-ray observatories. In particular, a unique probe of these regions is the gravitational radiation that is emitted by some compact stars very close to the black holes and which will could be surveyed by a millihertz gravitational wave interferometer scrutinizing the range of masses fundamental to the understanding of the origin and growth of supermassive black holes. By extracting the information carried by the gravitational radiation, we can determine the mass and spin of the central MBH with unprecedented precision and we can determine how the holes eat stars that happen to be near them.

研究动机与目标

• 理解低质量大质量黑洞（MBH）附近恒星的动力学，例如银河系中心的黑洞，尽管其与超大质量黑洞形成密切相关，但相关研究仍较为空白。
• 研究极端质量比旋进（EMRIs）的引力波辐射如何提供对中心MBH质量与自旋的精确测量。
• 评估恒星撕裂事件与气体吸积在MBH质量增长中的作用，尤其在质量较小的MBH系统中。
• 为即将开展的毫赫兹引力波任务与X射线望远镜建立理论框架，以探测MBH的吸积与演化过程。

提出的方法

• 利用后牛顿近似与测地线轨道动力学，建模致密星体通过引力辐射反作用向大质量黑洞旋进的过程。
• 应用引力波发射理论形式，从EMRI波形中提取中心MBH质量与自旋的信息。
• 分析在致密恒星环境中，恒星潮汐撕裂与气体吸积对MBH质量增长的影响。
• 将理论预测与未来毫赫兹引力波激光干涉仪及X射线望远镜的预期观测能力相结合。
• 利用EMRI的引力波信号作为探测时空几何结构与中心黑洞特性的工具。

实验结果

研究问题

• RQ1 低质量大质量黑洞附近的恒星动力学在多大程度上促进其质量增长与演化？
• RQ2 对极端质量比旋进（EMRIs）的引力波观测能在多大程度上以高精度测量中心MBH的质量与自旋？
• RQ3 恒星撕裂与气体吸积在星系核中如何为MBH提供物质供给？
• RQ4 如何利用未来的毫赫兹引力波任务与X射线观测台研究EMRIs与MBH吸积过程？

主要发现

• 极端质量比旋进（EMRIs）通过引力波观测为精确测量大质量黑洞的质量与自旋提供了独一无二的探测手段，精度前所未有。
• EMRIs的引力辐射可实现对MBH周围时空结构的详细测绘，为强引力场中恒星动力学提供深刻见解。
• 中心区域由潮汐力引发的恒星撕裂与气体吸积显著促进MBH的质量增长，尤其在低质量系统中更为重要。
• 未来的毫赫兹引力波激光干涉仪将对EMRI的探测与分析至关重要，使广义相对论在强场区域的直接检验成为可能。