Sgr A* near-infrared flares from reconnection events in a magnetically arrested disc
Sgr A* near-infrared flares from reconnection events in a magnetically arrested disc
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DOI：
10.1093/mnras/staa2288
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发表时间：
2020-06
影响因子：
4.8
通讯作者：
J. Dexter;J. Dexter;A. Tchekhovskoy;A. Jiménez-Rosales;S. Ressler;M. Bauböck;Y. Dallilar;P. D. Zeeuw;P. D. Zeeuw;F. Eisenhauer;S. Fellenberg;F. Gao;R. Genzel;R. Genzel;S. Gillessen;M. Habibi;T. Ott;J. Stadler;O. Straub;F. Widmann
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文献类型：
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作者：
J. Dexter;J. Dexter;A. Tchekhovskoy;A. Jiménez-Rosales;S. Ressler;M. Bauböck;Y. Dallilar;P. D. Zeeuw;P. D. Zeeuw;F. Eisenhauer;S. Fellenberg;F. Gao;R. Genzel;R. Genzel;S. Gillessen;M. Habibi;T. Ott;J. Stadler;O. Straub;F. Widmann
大振幅Sgr A* 近红外耀斑是由能量注入黑洞视界附近的电子引起的。天体测量数据表明，连续旋转的发射区在明亮的耀斑，和相应的旋转的线性偏振角。一个广泛的物理耀斑模型调用磁重联。在这里，我们表明，这样的情况下，可以出现在一个广义相对论磁流体动力学模拟的磁制动盘。磁通量的饱和触发喷发事件，其中磁主导的等离子体从地平线附近排出并形成旋转的螺旋结构。耗散通过在磁主导的等离子体和周围流体的界面处的重连而发生。这种耗散与Sgr A* 模型中近红外辐射的大幅增加有关，持续时间和振幅与观察到的耀斑一致。这样的事件发生在大致的时间尺度，以重新积累来自内部吸积盘的磁通量，10小时为Sgr A*。我们研究了一个样本事件的近红外观测表明，发射形态跟踪边界的磁主导区域。当该区域围绕黑洞旋转时，近红外质心和线性偏振角都经历连续旋转，类似于Sgr A* 耀斑中看到的行为。
Large-amplitude Sgr A* near-infrared flares result from energy injection into electrons near the black hole event horizon. Astrometry data show continuous rotation of the emission region during bright flares, and corresponding rotation of the linear polarization angle. One broad class of physical flare models invokes magnetic reconnection. Here we show that such a scenario can arise in a general relativistic magnetohydrodynamic simulation of a magnetically arrested disc. Saturation of magnetic flux triggers eruption events, where magnetically dominated plasma is expelled from near the horizon and forms a rotating, spiral structure. Dissipation occurs via reconnection at the interface of the magnetically dominated plasma and surrounding fluid. This dissipation is associated with large increases in near-infrared emission in models of Sgr A*, with durations and amplitudes consistent with the observed flares. Such events occur at roughly the timescale to re-accumulate the magnetic flux from the inner accretion disc, 10h for Sgr A*. We study near-infrared observables from one sample event to show that the emission morphology tracks the boundary of the magnetically dominated region. As the region rotates around the black hole, the near-infrared centroid and linear polarization angle both undergo continuous rotation, similar to the behavior seen in Sgr A* flares.