The dynamics of debris streams from tidal disruption events: exact solutions, critical stream density, and hydrogen recombination
The dynamics of debris streams from tidal disruption events: exact solutions, critical stream density, and hydrogen recombination
复制标题
潮汐破坏事件产生的碎片流动力学：精确解、临界流密度和氢重组
DOI：
10.1093/mnras/stad1347
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发表时间：
2023
影响因子：
4.8
通讯作者：
Coughlin, Eric R.
中科院分区：
文献类型：
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作者：
Coughlin, Eric R.
在潮汐破坏事件（TDE）中，一颗被超大质量黑洞（SMBH）摧毁的恒星转变成一种被称为潮汐破坏恒星碎片流的丝状结构。我们表明，当理想气体压力在流的热力学中占主导地位时，流体动力学方程有一个精确的解，该方程描述了流的演化，并解释了自重力、压力、气体的动态膨胀和流的横向结构。我们分析了该解对圆柱对称扰动的稳定性，并表明存在一个临界流密度，在此密度以下，流是不稳定的，并且不是自引力的；该临界密度比TDE中的流密度至少小40-50倍。在此临界密度以上，流是超稳定的，自重力限制了流，振荡周期呈指数长，超稳定尺度的增长率为1/6。超稳定性的幂律增长和小幂律指数表明流对圆柱对称扰动是有效稳定的。我们还使用这个解决方案来分析氢复合的影响，并提出，尽管复合大大增加了气体熵，但它可能无法完全消除自重力的影响。我们还表明，复合产生的瞬态远不如以前估计的那么明亮。
A star destroyed by a supermassive black hole (SMBH) in a tidal disruption event (TDE) is transformed into a filamentary structure known as a tidally disrupted stellar debris stream. We show that when ideal gas pressure dominates the thermodynamics of the stream, there is an exact solution to the hydrodynamics equations that describes the stream evolution and accounts for self-gravity, pressure, the dynamical expansion of the gas, and the transverse structure of the stream. We analyse the stability of this solution to cylindrically symmetric perturbations, and show that there is a critical stream density below which the stream is unstable and is not self-gravitating; this critical density is a factor of at least 40–50 smaller than the stream density in a TDE. Above this critical density the stream is overstable, self-gravity confines the stream, the oscillation period is exponentially long, and the growth rate of the overstability scales ast1/6. The power-law growth and small power-law index of the overstability implies that the stream is effectively stable to cylindrically symmetric perturbations. We also use this solution to analyse the effects of hydrogen recombination, and suggest that even though recombination substantially increases the gas entropy, it is likely incapable of completely destroying the influence of self-gravity. We also show that the transient produced by recombination is far less luminous than previous estimates.