Electron transport with re-acceleration and radiation in the jets of X-ray binaries
Electron transport with re-acceleration and radiation in the jets of X-ray binaries
复制标题
X 射线双星射流中的电子传输及再加速和辐射
DOI：
10.1093/mnras/stx2579
复制
发表时间：
2018
影响因子：
4.8
通讯作者：
Lu Ju Fu
中科院分区：
文献类型：
--
作者：
Zhang Jian Fu;Li Zhi Ren;Xiang Fu Yuan;Lu Ju Fu
本文通过湍流随机相互作用和激波碰撞研究了x射线双喷流中背景热电子的加速过程。通过考虑混合有波动磁场和有序大尺度磁场的湍流磁化射流，数值求解沿射流轴的输运方程，探讨了磁湍流、电子注入、加速区域位置和不同冷却速率等因素对加速效率的影响。结果表明：(1)射流中主导湍流磁场的存在是将背景热电子加速到相对论能量的必要条件。(2)电子的加速速率取决于磁流体动力学湍流类型，其中具有硬斜率的湍流类型可以更有效地加速电子。(3)有效加速区域应位于距中心黑洞10^3R_{\rm g}$的距离处（$R_{\rm g}$为引力半径）。由于加速速率与不同冷却速率的竞争，背景热电子不仅获得能量的增加，而且其光谱也超出了给定的初始分布，形成了类热分布。(4)本研究探索的加速机制可以合理地提供解释微类星体高能$\gamma$射线观测所需的电子最大能量，但为了预测可能的高能$\gamma$射线信号，需要采用一些极端参数。
This paper studies acceleration processes of background thermal electrons in X-ray binary jets via turbulent stochastic interactions and shock collisions. By considering turbulent magnetized jets mixed with fluctuation magnetic fields and ordered, large-scale one, and numerically solving the transport equation along the jet axis, we explore the influence of such as magnetic turbulence, electron injections, location of an acceleration region, and various cooling rates on acceleration efficiency. The results show that (1) the existence of the dominant turbulent magnetic fields in the jets is necessary to accelerate background thermal electrons to relativistic energies. (2) Acceleration rates of electrons depend on magnetohydrodynamic turbulence types, from which the turbulence type with a hard slope can accelerate electrons more effectively. (3) An effective acceleration region should be located at the distance $>10^3R_{\rm g}$ away from the central black hole ($R_{\rm g}$ being a gravitational radius). As a result of acceleration rates competing with various cooling rates, background thermal electrons obtain not only an increase in their energies but also their spectra are broadened beyond the given initial distribution to form a thermal-like distribution. (4) The acceleration mechanisms explored in this work can reasonably provide the electron maximum energy required for interpreting high-energy $\gamma$-ray observations from microquasars, but it needs to adopt some extreme parameters in order to predict a possible very high-energy $\gamma$-ray signal.