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arXiv 1604.04847astro-ph.HE
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GRB 091127多带余辉的模拟:硬电子能谱注入中断的证据

Modelling the Multi-band Afterglow of GRB 091127: Evidence of a Hard Electron Energy Spectrum with an Injection Break

Qiang Zhang, Yong-Feng Huang, Hong-Shi Zong

摘要:

伽玛暴的余辉被认为是由外流与外部介质相互作用产生的激波加速电子的同步辐射产生的。通常假设加速电子遵循指数为$p$的幂律能量分布。观测上,虽然大多数伽玛暴余辉的$p$大于2,但仍有少数伽玛暴显示出硬($p<2$)电子谱。GRB 091127,以及采样宽带余辉数据,显示了一个硬电子光谱和强大的光谱演化的证据,从高到低能量的光谱中断移动。光谱突变的演变非常快,不能解释的标准余辉模型中的冷却中断,除非不断变化的微物理参数的假设。此外,多波段余辉光变曲线在33k附近出现消色差突变。基于具有注入间断的硬电子能谱模型,我们将观测到的谱间断解释为注入间断对应的同步辐射频率,将消色差间断解释为由喷流边缘效应引起的喷流间断。结果表明,该模型能较好地再现GRB 091127的光谱演化和多带余辉光变曲线。

英文摘要:

The afterglow of GRBs is believed to originate from the synchrotron emission of shock-accelerated electrons produced by the interaction between the outflow and the external medium. The accelerated electrons are usually assumed to follow a power law energy distribution with an index of $p$. Observationally, although most GRB afterglows have a $p$ larger than 2, there are still a few GRBs suggestive of a hard ($p<2$) electron spectrum. GRB 091127, with well-sampled broad-band afterglow data, shows evidence of a hard electron spectrum and strong spectral evolution, with a spectral break moving from high to lower energies. The spectral break evolves very fast and cannot be explained by the cooling break in the standard afterglow model, unless evolving microphysical parameters are assumed. Besides, the multi-band afterglow light curves show an achromatic break at around 33 ks. Based on the model of a hard electron spectrum with an injection break, we interpret the observed spectral break as the synchrotron frequency corresponding to the injection break, and the achromatic break as a jet break caused by the jet-edge effect. It is shown that the spectral evolution and the multi-band afterglow light curves of GRB 091127 can be well reproduced by this model.

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