Tidal Disruption Events from Eccentric Orbits and Lessons Learned from the Noteworthy ASASSN-14ko
Tidal Disruption Events from Eccentric Orbits and Lessons Learned from the Noteworthy ASASSN-14ko
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DOI：
10.3847/1538-4357/acafe1
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发表时间：
2022-06
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通讯作者：
Chang 畅 Liu 刘;B. Mockler;E. Ramirez-Ruiz;R. Yarza;J. Law-Smith;S. Naoz;D. Melchor;Sanaea C. Rose
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作者：
Chang 畅 Liu 刘;B. Mockler;E. Ramirez-Ruiz;R. Yarza;J. Law-Smith;S. Naoz;D. Melchor;Sanaea C. Rose
在束缚轨道上掠过超大质量黑洞（SMBH）的恒星可能会在潮汐破坏中幸存下来，导致周期性的耀斑。受最近发现的周期性核瞬变ASASSN-14 ko的启发，我们研究了偏心轨道上接近SMBH的恒星的潮汐变形。用解析和流体动力学方法，我们证明了当离心率大于某一临界值时，星星的整体潮汐形变与抛物轨道中的潮汐形变相似。这使得人们可以利用现有的模拟库，从抛物面遇到计算质量回落率在偏心的TDE。我们发现偏心TDEs的耀斑结构表现出复杂的依赖于SMBH质量和轨道周期。对于恒星轨道SMBH相对较短的周期，我们预测寿命显着较短的持续时间比那些在抛物线的TDEs，这可以用来预测重复事件，如果SMBH的质量可以独立测量耀斑。利用绝热质量损失模型，我们研究了耀斑在多次通道中的演化，并表明演化恒星比主序星可以存活更多的通道。我们将这一理论框架应用于重复的TDE候选者ASASSN-14 ko，并认为它的周期性耀斑起源于一个中等质量（M <$1 M <$），扩展（可能是10 R <$），进化的星星在一个掠食，围绕SMBH的束缚轨道。未来的多潮汐相互作用的流体动力学模拟将使单个耀斑结构和多个耀斑的演变的现实模型。
Stars grazing supermassive black holes (SMBHs) on bound orbits may survive tidal disruption, causing periodic flares. Inspired by the recent discovery of the periodic nuclear transient ASASSN-14ko, a promising candidate for a repeating tidal disruption event (TDE), we study the tidal deformation of stars approaching SMBHs on eccentric orbits. With both analytical and hydrodynamic methods, we show the overall tidal deformation of a star is similar to that in a parabolic orbit provided that the eccentricity is above a critical value. This allows one to make use of existing simulation libraries from parabolic encounters to calculate the mass fallback rate in eccentric TDEs. We find the flare structures of eccentric TDEs show a complicated dependence on both the SMBH mass and the orbital period. For stars orbiting SMBHs with relatively short periods, we predict significantly shorter-lived duration flares than those in parabolic TDEs, which can be used to predict repeating events if the mass of the SMBH can be independently measured. Using an adiabatic mass-loss model, we study the flare evolution over multiple passages, and show the evolved stars can survive many more passages than main-sequence stars. We apply this theoretical framework to the repeating TDE candidate ASASSN-14ko and suggest that its recurrent flares originate from a moderately massive (M ≳ 1 M ⊙), extended (likely ≈10 R ⊙), evolved star on a grazing, bound orbit around the SMBH. Future hydrodynamic simulations of multiple tidal interactions will enable realistic models on the individual flare structure and the evolution over multiple flares.