论文标题
跌落区域的非热发射：黑洞X射线二进制软状态的高能尾部的模型
Nonthermal emission from the plunging region: a model for the high-energy tail of black hole X-ray binary soft states
论文作者
论文摘要
X射线二进制文件具有柔软的光谱状态，其中包括1 KEV的热黑体发射，而kev上方的幂律尾巴则包括尾尾。经验模型将高能量的幂尾符合到非热电子分布的辐射，但是非热电子的物理位置以及其幂律指数和高能量截止的原因仍然很大程度上是未知的。在这里，我们提出，非热电子来自黑洞最内向的稳定圆形轨道（“跌落区域”）。使用来自粒子中的粒子模拟的下降区域动力学和电子分布函数的分析模型，我们概述了一个可以重现观察到的光谱特征的稳态模型。特别是，我们的模型重现了$γ\ gtrsim2 $的光子指数和幂律发光度，符合强磁场的磁盘发光度的数百分之几，与柔软状态的观察一致。因为发射源于黑洞如此近，所以我们预测幂律光度应在很大程度上取决于系统倾斜角度和黑洞旋转。该模型可以扩展到在X射线二进制文件的硬状态下观察到的400 KEV以上的幂律尾巴。
X-ray binaries exhibit a soft spectral state comprising thermal blackbody emission at 1 keV and a power-law tail above 10 keV. Empirical models fit the high-energy power-law tail to radiation from a nonthermal electron distribution, but the physical location of the nonthermal electrons and the reason for their power-law index and high-energy cut-off are still largely unknown. Here, we propose that the nonthermal electrons originate from within the black hole's innermost stable circular orbit (the ''plunging region''). Using an analytic model for the plunging region dynamics and electron distribution function properties from particle-in-cell simulations, we outline a steady-state model that can reproduce the observed spectral features. In particular, our model reproduces photon indices of $Γ\gtrsim2$ and power-law luminosities on the order of a few percent of the disk luminosity for strong magnetic fields, consistent with observations of the soft state. Because the emission originates so close to the black hole, we predict that the power-law luminosity should strongly depend on the system inclination angle and black hole spin. This model could be extended to the power-law tails observed above 400 keV in the hard state of X-ray binaries.
