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arXiv 1907.03312astro-ph.GAastro-ph.HE
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潮汐破裂事件,主序星极端质量比吸气和星系核中的双星破裂

Tidal disruption events, main-sequence extreme-mass ratio inspirals and binary star disruptions in galactic nuclei

Re'em Sari, Giacomo Fragione

摘要:

近年来,银河系中心一直受到严格的审查,这要归功于前所未有的任务,这些任务旨在测量超大质量黑洞(SMBH)附近的气体和恒星动力学,并寻找螺旋状恒星黑洞的引力波(GW)特征。在星系核的拥挤环境中,两体相互作用改变了恒星在长时间尺度上的分布,使它们在能量和角动量上漂移。本文提出了一种简化的分析处理银河系恒星核的散射过程,假设所有的恒星都有相同的质量。我们讨论了两体弛豫和引力波发射之间的相互作用如何改变SMBH影响范围内的内部恒星尖点的斜率,并计算了被SMBH潮汐干扰的恒星的潮汐干扰事件(TDE)和主序星极端质量比吸气(MS-EMRI)的速率。我们发现,通常的TDE和MS-EMRI率的比率是潮汐和史瓦西半径的比率的平方。对于我们的银河系,这意味着MS-EMRI的比率仅为TDE比率的1%左右。然后,我们考虑的作用,由于希尔斯二进制中断机制的SMBH附近的高偏心轨道上注入的恒星,并表明,MS-EMRI率几乎可以接近TDE率,如果在SMBH的影响半径的二进制部分接近统一。最后,我们讨论了物理恒星碰撞影响相空间的大面积。

英文摘要:

The Galactic Center has been under intense scrutiny in the recent years thanks to the unprecedented missions aiming at measuring the gas and star dynamics near the supermassive black hole (SMBH) and at finding gravitational wave (GW) signatures of inspiralling stellar black holes. In the crowded environment of galactic nuclei, the two-body interactions alter the distribution of stars on long timescales, making them drift in energy and angular momentum. We present a simplified analytical treatment of the scattering processes in galactic stellar nuclei, assuming all stars have the same mass. We have discussed how the interplay between two-body relaxation and gravitational wave emission modifies the slope of the inner stellar cusp within the SMBH sphere of influence, and calculated the rates of tidal disruption events (TDEs) and main-sequence extreme-mass ratio inspirals (MS-EMRIs) of stars that are tidally disrupted by the SMBH. We find that typically the ratio of the TDE and MS-EMRI rates is the square of the ratio of the tidal and Schwarzschild radii. For our Galaxy, this implies that the rate of MS-EMRIs is just about a percent of the TDE rate. We then consider the role of stars injected on highly eccentric orbits in the vicinity of the SMBH due to Hills binary disruption mechanism, and show that the MS-EMRI rate can almost approach the TDE rate if the binary fraction at the SMBH influence radius is close to unity. Finally, we discuss that physical stellar collisions affect a large area of phase space.

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