Cooling Envelope Model for Tidal Disruption Events
Cooling Envelope Model for Tidal Disruption Events
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DOI：
10.3847/2041-8213/ac90ba
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发表时间：
2022-07
期刊：
影响因子：
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通讯作者：
B. Metzger
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作者：
B. Metzger
我们提出了一个玩具模型的热光学/紫外/X射线辐射的潮汐破坏事件（TDEs）。受最近流体动力学模拟的启发，我们假设碎片流迅速地循环（在最紧密结合的碎片的轨道周期上），在超大质量黑洞（SMBH）周围产生一个半径为R v <$1014 cm（光球半径<$1015 cm）的热准球形压力支持包络。当包层辐射冷却时，它经历开尔文-亥姆霍兹收缩R v <$t −1，温度上升T eff <$t 1/2，而总光度大致保持不变;光学光度衰减为νLν <$Rv 2 T eff <$t−3/2。尽管这与质量回落速率M fb <$t−5/3相似，但回落吸积的包层加热与包层冷却光度相比是次要的，除了在光学峰值附近（在那里它们是可比的）。包层收缩可以通过从内包层到SMBH上的吸积能量注入以调节的方式延迟，导致光学/X射线光变曲线的后期平坦化，类似于在一些TDE中观察到的。最后，当包层收缩到接近圆化半径时，SMBH吸积率上升到最大值，同时光学光度下降。这种冷却引起的（而不是循环引起的）长达几百天的延迟可能解释了在一些TDE中观察到的热X射线，晚期射电耀斑和高能中微子产生的延迟。我们比较模型预测最近的TDE光曲线相关性研究，发现协议和紧张点。
We present a toy model for the thermal optical/UV/X-ray emission from tidal disruption events (TDEs). Motivated by recent hydrodynamical simulations, we assume that the debris streams promptly and rapidly circularize (on the orbital period of the most tightly bound debris), generating a hot quasi-spherical pressure-supported envelope of radius R v ∼ 1014 cm (photosphere radius ∼1015 cm) surrounding the supermassive black hole (SMBH). As the envelope cools radiatively, it undergoes Kelvin–Helmholtz contraction R v ∝ t −1, its temperature rising T eff ∝ t 1/2 while its total luminosity remains roughly constant; the optical luminosity decays as νLν∝Rv2Teff∝t−3/2 . Despite this similarity to the mass fallback rate Ṁfb∝t−5/3 , envelope heating from fallback accretion is subdominant compared to the envelope cooling luminosity except near optical peak (where they are comparable). Envelope contraction can be delayed by energy injection from accretion from the inner envelope onto the SMBH in a regulated manner, leading to a late-time flattening of the optical/X-ray light curves, similar to those observed in some TDEs. Eventually, as the envelope contracts to near the circularization radius, the SMBH accretion rate rises to its maximum, in tandem with the decreasing optical luminosity. This cooling-induced (rather than circularization-induced) delay of up to several hundred days may account for the delayed onset of thermal X-rays, late-time radio flares, and high-energy neutrino generation, observed in some TDEs. We compare the model predictions to recent TDE light-curve correlation studies, finding both agreement and points of tension.