Bulk motion Comptonization in black hole accretion flows
Bulk motion Comptonization in black hole accretion flows
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DOI：
10.1111/j.1365-2966.2005.09752.x
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发表时间：
2005-07
影响因子：
4.8
通讯作者：
A. Niedźwiecki;A. Zdziarski
中科院分区：
文献类型：
--
作者：
A. Niedźwiecki;A. Zdziarski
本文研究了冷电子径向自由落在黑洞上的软光子康普顿化产生的谱。我们使用的蒙特卡罗方法涉及完全相对论性的描述Comptonization的克尔时空。与前人的研究一致，我们发现自由落体运动的康普顿化产生光子指数为Γ ≥ 3的幂律谱。与以前的一些研究相反，我们发现这些幂律谱仅扩展到能量«m e c 2。我们指出，在几十千电子伏的这种光谱的通用截止导致几种效果，无论在模型中的物理参数的任何特定值。这种产生能量≥100 keV的光子的低效率排除了体运动康普顿化作为黑洞双星软谱态中主要辐射过程的可能性。相对于周围圆盘的黑体发射峰值的幂律（低于截止值）的归一化通常非常低，除了圆盘和等离子体之间具有重叠的模型，在这种情况下光谱非常软，r ≥ 4。
We study spectra generated by Comptonization of soft photons by cold electrons radially free falling on to a black hole. We use a Monte Carlo method involving a fully relativistic description of Comptonization in the Kerr space-time. In agreement with previous studies, we find that Comptonization on the bulk motion of free fall gives rise to power-law spectra with the photon index of Γ ≥ 3. In contrast to some previous studies, we find that these power-law spectra extend only to energies «m e c 2 . We indicate several effects resulting in generic cut-offs of such spectra at several tens of keV, regardless of any specific values of physical parameters in the model. This inefficiency of producing photons with energies ≥100 keV rules out bulk motion Comptonization as a main radiative process in soft spectral states of black hole binaries. The normalization of the power law (below the cut-off) with respect to the peak of the blackbody emission of the surrounding disc is typically very low, except for models with an overlap between the disc and the plasma, in which case the spectra are very soft, Γ ≥ 4.