General relativistic MHD simulations of non-thermal flaring in Sagittarius A*
General relativistic MHD simulations of non-thermal flaring in Sagittarius A*
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DOI：
10.1093/mnras/stab2466
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发表时间：
2020-11
影响因子：
4.8
通讯作者：
K. Chatterjee;S. Markoff;J. Neilsen;Z. Younsi;G. Witzel;A. Tchekhovskoy;D. Yoon;A. Ingram;
中科院分区：
文献类型：
--
作者：
K. Chatterjee;S. Markoff;J. Neilsen;Z. Younsi;G. Witzel;A. Tchekhovskoy;D. Yoon;A. Ingram;
Sgr A*在其多波长发射中表现出规律的变化，包括每日的x射线耀斑和大致连续的近红外（NIR）闪烁。由于逆康普顿辐射和同步辐射都是可能的辐射机制，这种可变性的起源仍然是不明确的。潜在的粒子分布也没有很好地约束，特别是非热贡献。在这项工作中，我们首次使用gpu加速的广义相对论磁流体动力学代码H-AMR对Sgr a *的高分辨率3D模拟进行了耀斑通量分布的研究，包括粒子加速的影响。对于粒子加速，我们使用广义相对论射线追踪代码来执行辐射传递，假设热电子+非热电子能量混合分布。我们提取了亚毫米、近红外和x射线波段的~ 60 h光曲线，并将光曲线的功率谱和累积通量分布与Sgr A*耀斑的统计描述进行了比较。我们的研究结果表明，弱磁化吸积流中由湍流驱动重连接产生的非热电子群导致了中等的近红外和x射线耀斑，并合理地描述了x射线通量分布，同时满足多波长通量约束。这些模型在近红外和x射线中都表现出较高的rms %振幅，$\gtrsim $ 150{{\ \ rrm $ %}}$，吸积速率的变化驱动了230 GHz通量的变化，与Sgr A*的观测结果一致。
Sgr A* exhibits regular variability in its multiwavelength emission, including daily X-ray flares and roughly continuous near-infrared (NIR) flickering. The origin of this variability is still ambiguous since both inverse Compton and synchrotron emission are possible radiative mechanisms. The underlying particle distributions are also not well constrained, particularly the non-thermal contribution. In this work, we employ the GPU-accelerated general relativistic magnetohydrodynamics code H-AMR to perform a study of flare flux distributions, including the effect of particle acceleration for the first time in high-resolution 3D simulations of Sgr A*. For the particle acceleration, we use the general relativistic ray-tracing code bhoss to perform the radiative transfer, assuming a hybrid thermal+non-thermal electron energy distribution. We extract ∼60 h light curves in the sub-millimetre, NIR and X-ray wavebands, and compare the power spectra and the cumulative flux distributions of the light curves to statistical descriptions for Sgr A* flares. Our results indicate that non-thermal populations of electrons arising from turbulence-driven reconnection in weakly magnetized accretion flows lead to moderate NIR and X-ray flares and reasonably describe the X-ray flux distribution while fulfilling multiwavelength flux constraints. These models exhibit high rms per cent amplitudes, $\gtrsim 150{{\ \rm per\ cent}}$ both in the NIR and the X-rays, with changes in the accretion rate driving the 230 GHz flux variability, in agreement with Sgr A* observations.