We investigate the radiation fields around super-Eddington accretion flow, in which multiple inverse-Compton scattering plays a principal role, by using newly developed code describing Boltzmann radiation transfer in the Schwarzschild space-time. We apply this code to post-processing spectral calculations based on general relativistic, radiation magnetohydrodynamic simulation data to obtain X-ray spectra seen from various viewing angles. The radiation fields are distinctively separated into a funnel region with an opening angle of ∼30°, which is full with hot (gas temperature of T > 108 K), tenuous, and high-velocity plasmas, and surrounding cooler (T ∼ 107 K) and optically thick outflow regions. Accordingly, there is a clear tendency that the smaller the viewing angle, the harder the spectra. In particular, hard photons with several tens of keV are observable only by observers at viewing angles less than ∼30°, consistent with past spectral studies based on simulations. Further, we investigate how the spectra are varied by a flare occurring in the innermost region, finding that the variation amplitude grows as the photon energy increases and that the harder photons emerge more quickly than softer photons. The observational implications on long-term spectral variability of ultra-luminous X-ray sources are briefly discussed.

中文翻译：

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超级爱丁顿吸积体康普顿化 X 射线光谱的变异性：使用玻尔兹曼辐射传输的方法

我们通过使用描述史瓦西时空中玻尔兹曼辐射转移的新开发的代码来研究超级爱丁顿吸积流周围的辐射场，其中多次逆康普顿散射起主要作用。我们将此代码应用于基于广义相对论辐射磁流体动力学模拟数据的后处理光谱计算，以获得从各种视角看到的 X 射线光谱。辐射场明显地分成一个漏斗区域，其张角约为 30°，充满热（气体温度 T > 108 K）、稀薄和高速等离子体，周围较冷（T ∼ 107 K) 和光学厚的流出区域。因此，存在视角越小光谱越硬的明显趋势。特别是，几十 keV 的硬光子只能被观察者以小于 30° 的视角观察到，这与过去基于模拟的光谱研究一致。此外，我们研究了光谱如何因发生在最内部区域的耀斑而变化，发现变化幅度随着光子能量的增加而增加，并且较硬的光子比较软的光子出现得更快。简要讨论了对超发光 X 射线源的长期光谱变异性的观测意义。发现变化幅度随着光子能量的增加而增加，并且较硬的光子比较软的光子出现得更快。简要讨论了对超发光 X 射线源的长期光谱变异性的观测意义。发现变化幅度随着光子能量的增加而增加，并且较硬的光子比较软的光子出现得更快。简要讨论了对超发光 X 射线源的长期光谱变异性的观测意义。