外磁场中伽马射线暴瞬发的宽带模拟
Broad band simulation of Gamma Ray Bursts (GRB) prompt emission in presence of an external magnetic field
摘要：
伽玛暴瞬发辐射的起源至今还不清楚。最简单和最流行的模型是同步加速器，自康普顿（SSC）的超相对论性喷流内的内部冲击产生的排放。然而，最近对延迟的高能量成分的观测鼓励了替代模型。在这里，我们使用最近开发的相对论冲击公式来模拟伽玛暴。它考虑了诸如碰撞壳层密度、电场和磁场等量的演化。我们还通过考虑旋进外部磁场来扩展以前的公式。这些模拟是非常现实的，并提出了显着的改善相对于以前的现象学伽玛暴模拟。它们再现了E > E_{peak}时真实伽玛暴分离峰的光变曲线和观测到的各种光谱斜率。高能量发射可以用同步辐射和逆康普顿的次优势贡献来解释。我们还提出了一个解释的费米-LAT仪器观察到的扩展尾部发射，并将其与屏蔽的磁场和/或捕获的加速电子的电磁能量结构中的等离子体在冲击波阵面。在E E_{peak}处的模拟爆发的光谱斜率与理论预测一致，并且在E < E_{peak}处，如果电子的光谱大致平坦或具有浅斜率，则可以更平坦。在软伽马射线和硬X射线波段观察到的平坦光谱证明，在$E < E_{peak}$处存在来自电子分布的较低洛伦兹因子翼的显著贡献，所述较低洛伦兹因子翼具有大致随机的加速度而不是热的。这意味着喷射时物质的状态很可能是非热的，电子在低能量下具有浅光谱。（略）
英文摘要：
The origin of prompt emission in GRBs is not yet well understood. The simplest and most popular model is Synchrotron, Self-Compton (SSC) emission produced by internal shocks inside an ultra-relativistic jet. However, recent observations of a delayed high energy component have encouraged alternative models. Here we use a recently developed formulation of relativistic shocks to simulate GRBs. It takes into account the evolution of quantities such as densities of colliding shells, electric and magnetic fields. We also extend the previous formulation by considering a precessing external magnetic field. These simulations are very realistic and present significant improvement with respect to previous phenomenological GRB simulations. They reproduce light curves of separated peaks of real GRBs and variety of observed spectral slopes at E > E_{peak}. The high energy emission can be explained by synchrotron emission and a subdominant contribution from inverse Compton. We also suggest an explanation for the extended tail emission observed by the Fermi-LAT instrument and relate it to the screening of the magnetic field and/or trapping of accelerated electrons in the electromagnetic energy structure of the plasma in the shock front. Spectral slopes of simulated bursts at E << E_{peak} are consistent with theoretical prediction and at E < E_{peak} can be flatter if the spectrum of electrons is roughly flat or has a shallow slope. The observed flat spectra at soft gamma-ray and hard x-ray bands is the evidence that there is a significant contribution at $E < E_{peak}$ from lower Lorentz factor wing of electrons distribution which have a roughly random acceleration rather than being thermal. This means that the state of matter in the jet at the time of ejection is most probably nonthermal and electrons have a shallow spectrum at low energies.(abbreviated)
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