An asymmetric electron-scattering photosphere around optical tidal disruption events
An asymmetric electron-scattering photosphere around optical tidal disruption events
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DOI：
10.1038/s41550-022-01767-z
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发表时间：
2022-07
期刊：
影响因子：
14.1
通讯作者：
G. Leloudas;M. Bulla;A. Cikota;L. Dai;L. L. Thomsen-L.;J. Maund;P. Charalampopoulos;Nathaniel Roth;I. Arcavi;K. Auchettl;D. Malesani;M. Nicholl;E. Ramirez-Ruiz
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文献类型：
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作者：
G. Leloudas;M. Bulla;A. Cikota;L. Dai;L. L. Thomsen-L.;J. Maund;P. Charalampopoulos;Nathaniel Roth;I. Arcavi;K. Auchettl;D. Malesani;M. Nicholl;E. Ramirez-Ruiz
当一颗星星穿过超大质量黑洞的潮汐半径时，伴随着辐射的爆发，它将被剧烈地撕裂。现在已经在光学波长中确定了几十个这样的潮汐破坏事件，但强烈光学发射的确切起源仍然没有定论。在这里，我们报告偏振观测三个潮汐破坏事件。连续偏振与波长无关，而发射线部分去偏振。这些特征与光子在自由电子的包络中被散射和极化是一致的。一个几乎轴对称的光球从不同的角度来看，是在广泛的协议与数据，但也有证据表明，偏离轴对称之前的耀斑和显着的时间演化的高峰期，在早期，兼容的吸积盘的快速形成。通过结合一个超爱丁顿吸积模型与辐射传输代码，我们模拟的偏振度作为磁盘质量和视角的函数，我们表明，预测的水平是兼容的观测扩展后处理信封的~1,000引力半径。因此，分光偏振技术构成了对潮汐扰动事件模型的一种新的观测检验，为潮汐扰动事件的研究开辟了一条重要的新的探索途径。
A star crossing the tidal radius of a supermassive black hole will be spectacularly ripped apart with an accompanying burst of radiation. A few tens of such tidal disruption events have now been identified in optical wavelengths, but the exact origin of the strong optical emission remains inconclusive. Here we report polarimetric observations of three tidal disruption events. The continuum polarization appears independent of wavelength, while emission lines are partially depolarized. These signatures are consistent with photons being scattered and polarized in an envelope of free electrons. An almost axisymmetric photosphere viewed from different angles is in broad agreement with the data, but there is also evidence for deviations from axial symmetry before the peak of the flare and significant time evolution at early times, compatible with the rapid formation of an accretion disk. By combining a super-Eddington accretion model with a radiative transfer code, we simulate the polarization degree as a function of disk mass and viewing angle and we show that the predicted levels are compatible with the observations for extended reprocessing envelopes of ~1,000 gravitational radii. Spectropolarimetry therefore constitutes a new observational test for tidal disruption event models, and opens an important new line of exploration in the study of tidal disruption events.