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arXiv 2212.05079astro-ph.HE
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基于碰撞诱导外流模式的潮汐破裂事件连续极化水平模拟

Modeling continuum polarization levels of tidal disruption events based on the collision-induced outflow mode

Panos Charalampopoulos, Mattia Bulla, Clement Bonnerot, Giorgos Leloudas

摘要:

TDE在光学和UV中已经被观察了十多年,但其潜在的发射机制仍然是一个谜。有人认为视角效应可能解释它们巨大的光度和光谱多样性。偏振确实是敏感的视角和第一偏振研究的TDEs现在可用,需要一个理论解释。在这项研究中,我们使用的辐射转移代码POSSIS和碰撞诱导外流(CIO)的TDE排放的情况下,未绑定的冲击气体起源于碎片流的交叉点偏移的黑洞,再加工的硬排放吸积流到紫外和光学波段的TDE的连续偏振水平。我们探讨了两种不同的情况下,峰值质量回落率M 'P(~3和~0.3 Msol/yr),同时改变以下几何参数:从黑洞(BH)的距离R_int的交点,黑洞周围的光球半径R_ph,在其表面上的光子产生,和开角Deltheta(各向异性发射)。对于高质量回退率的情况,我们发现对于10/12模拟,每个视角的偏振水平低于1(P<1%)并且P<0.5%。在赤道视角下,偏振的绝对值达到最大值(P_max)。对于低质量回退率情况,预测的最大值为P~8.8%,并且在中间视角达到P_max。我们发现偏振强烈地依赖于i)由不同的M 'p值设置的中心区域处的光学深度和ii)视角。最后,通过将我们的模型预测与几个TDEs的偏振观测进行比较,我们试图约束它们所观测到的视角,并且我们表明多历元偏振观测可以成为约束TDEs视角的关键因素。

英文摘要:

TDEs have been observed in the optical and UV for more than a decade but the underlying emission mechanism still remains a puzzle. It has been suggested that viewing angle effects could potentially explain their large photometric and spectroscopic diversity. Polarization is indeed sensitive to the viewing angle and the first polarimetry studies of TDEs are now available, calling for a theoretical interpretation. In this study, we model the continuum polarization levels of TDEs using the radiative transfer code POSSIS and the collision-induced outflow (CIO) TDE emission scenario where unbound shocked gas originating from a debris stream intersection point offset from the black hole, reprocesses the hard emission from the accretion flow into UV and optical bands. We explore two different cases of peak mass fallback rates M'p (~3 and ~0.3 Msol/yr) while varying the following geometrical parameters: the distance R_int from the black hole (BH) to the intersection point, the radius of the photosphere around the BH R_ph, on the surface of which the photons are generated, and the opening angle Deltheta (anisotropic emission). For the high mass fallback rate case, we find for every viewing angle polarization levels below one (P<1%) and P<0.5% for 10/12 simulations. The absolute value of polarization reaches its maximum (P_max) for equatorial viewing angles. For the low mass fallback rate case, the maximum value predicted is P~8.8% and P_max is reached for intermediate viewing angles. We find that the polarization depends strongly on i) the optical depths at the central regions set by the different M'p values and ii) the viewing angle. Finally, by comparing our model predictions to polarization observations of a few TDEs, we attempt to constrain their observed viewing angles and we show that multi-epoch polarimetric observations can become a key factor in constraining the viewing angle of TDEs.

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