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arXiv 1405.0844astro-ph.HE
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磁支配射流模型中GRB极化角的变化

The change of GRB polarization angles in the magnetic-dominated jet model

Zhe Chang, Hai-Nan Lin

摘要:

对GRB 100826 A瞬发相的偏振测量表明,在两个相邻的时间间隔内,偏振角变化为$\sim 90^{\circ}$。我们将表明,这种现象可以很自然地解释的框架内的磁主导射流(MDJ)模型。MDJ模型表明,流出的体积洛伦兹因子随着$Γ\propto r^{1/3}$而增加,直到达到饱和值$Γ_{\rm sat}$。电子在由中央发动机喷射的平流输送的全局有序磁场中移动,并产生同步加速器光子。偏振的同步加速器光子沿着喷流方向传播,然后与喷流前端的冷电子碰撞。在康普顿散射过程之后,这些光子从喷流中逃逸,并被稍微离轴的观察者检测到。如果光子在体洛伦兹因子饱和之前发射,则偏振角的改变是流出加速的自然结果。

英文摘要:

The polarimetric measurement on the prompt phase of GRB 100826A shows that the polarization angle changes $\sim 90^{\circ}$ between two adjacent time intervals. We will show that this phenomenon can be naturally interpreted in the framework of the magnetic-dominated jet (MDJ) model. The MDJ model suggests that the bulk Lorentz factor of the outflow increases as $Γ\propto r^{1/3}$, until reaching a saturated value $Γ_{\rm sat}$. Electrons move in the globally ordered magnetic field advected by the jet from the central engine and produce synchrotron photons. The polarized synchrotron photons travel alone the jet direction and then collide with the cold electrons at the front of the jet. After the Compton scattering process, these photons escape from the jet and are detected by the observer locating slightly off-axis. If photons are emitted before the bulk Lorentz factor saturates, the change of polarization angle is a natural result of the acceleration of the outflow.

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