Electromagnetic Signatures from Supermassive Binary Black Holes Approaching Merger
Electromagnetic Signatures from Supermassive Binary Black Holes Approaching Merger
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DOI：
10.3847/1538-4357/ac56de
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发表时间：
2021-12
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通讯作者：
Eduardo M. Guti'errez;L. Combi;S. Noble;M. Campanelli;J. Krolik;F. L. Lopez Armengol;F. Garc'ia
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作者：
Eduardo M. Guti'errez;L. Combi;S. Noble;M. Campanelli;J. Krolik;F. L. Lopez Armengol;F. Garc'ia
我们对处于合并边缘的自旋和非自旋超大质量双星黑洞周围的吸积盘产生的电磁辐射给出了完全相对论的预测。我们使用Bothros程序对三维广义相对论磁流体模拟的数据进行后处理，通过光线跟踪计算。这些模拟模拟了一个环行双星圆盘和围绕两个等质量黑洞形成的迷你圆盘的动力学，这些黑洞的初始间距为20个引力半径，并在自旋状态下将系统演化了10多个轨道。我们将辐射模拟为光学厚度吸积盘发射的热黑体辐射和光学薄热日冕发射的硬X射线的幂函数谱之和。我们在不同的频率产生与时间相关的光谱、图像和光曲线，以研究发射中的本征周期信号，以及黑洞自旋的影响。我们发现，递进的黑洞自转使迷你盘变得更亮，因为更小的最内侧稳定的圆形轨道角动量需要更多的耗散才能使物质跳入地平线。然而，与带有旋转黑洞的较大分离双星中的迷你盘相比，我们的迷你盘的亮度较低：与那些系统不同，它们的质量吸积率低于外双星盘，而且它们的辐射效率较低，因为它们的流入时间更短。与质量和吸积率相匹配的单个黑洞系统相比，这些双星在紫外线下的光谱明显更弱和更软。最后，我们讨论了我们的发现对这些系统的潜在可观测性的影响。
We present fully relativistic predictions for the electromagnetic emission produced by accretion disks surrounding spinning and nonspinning supermassive binary black holes on the verge of merging. We use the code Bothros to post-process data from 3D general relativistic magnetohydrodynamic simulations via ray-tracing calculations. These simulations model the dynamics of a circumbinary disk and the mini-disks that form around two equal-mass black holes orbiting each other at an initial separation of 20 gravitational radii, and evolve the system for more than 10 orbits in the inspiral regime. We model the emission as the sum of thermal blackbody radiation emitted by an optically thick accretion disk and a power-law spectrum extending to hard X-rays emitted by a hot optically thin corona. We generate time-dependent spectra, images, and light curves at various frequencies to investigate intrinsic periodic signals in the emission, as well as the effects of the black hole spin. We find that prograde black hole spin makes mini-disks brighter since the smaller innermost stable circular orbit angular momentum demands more dissipation before matter plunges to the horizon. However, compared to mini-disks in larger separation binaries with spinning black holes, our mini-disks are less luminous: unlike those systems, their mass accretion rate is lower than in the circumbinary disk, and they radiate with lower efficiency because their inflow times are shorter. Compared to a single black hole system matched in mass and accretion rate, these binaries have spectra noticeably weaker and softer in the UV. Finally, we discuss the implications of our findings for the potential observability of these systems.