The Time-resolved Spectra of Photospheric Emission from a Structured Jet for Gamma-Ray Bursts
The Time-resolved Spectra of Photospheric Emission from a Structured Jet for Gamma-Ray Bursts
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伽马射线暴结构射流光球发射的时间分辨光谱
DOI：
10.3847/1538-4357/ab30c7
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发表时间：
2019-04
影响因子：
4.9
通讯作者：
Zhang Bin Bin
中科院分区：
文献类型：
--
作者：
Meng Yan Zhi;Lu Liang Duan;Wei Jun Jie;Wu Xue Feng;Zhang Bin Bin
在许多费米伽玛射线暴中发现的准热成分意味着光球辐射确实对许多伽玛射线暴的瞬发有贡献。但能否用能带函数或截止幂律经验拟合观测到的光谱，特别是光谱和峰值能量（Ep）的演化，仅用光球辐射模型来解释，还有待进一步讨论。在这项工作中，我们详细调查的时间分辨光谱和Ep演变的光球发射的结构射流，具有内部恒定和外部递减的角度洛伦兹因子的配置文件。此外，一个连续的风与时间相关的风光度已被认为是。结果表明，光球在峰值附近的光谱类似于幂律截止光谱。该光谱可以具有观测到的平均低能光谱指数α <$−1，并且我们的光球模型中低能光谱指数的分布与观测到的（−2 <$α <$0）相似。此外，衰变阶段的两种谱演化（以核宽θc分隔）分别与几个Fermi多脉冲和单脉冲伽玛暴的时间分辨谱分析结果一致。对于这个光球模型，我们也能很好地再现观测到的两种Ep演化模式。因此，通过考虑光球发射的结构喷流，我们再现的观测以及最适合的截止幂律模型的峰值通量谱或时间积分谱的伽玛暴。
The quasi-thermal components found in many Fermi gamma-ray bursts (GRBs) imply that the photosphere emission indeed contributes to the prompt emission of many GRBs. But whether the observed spectra empirically fitted by the Band function or cutoff power law, especially the spectral and peak energy (Ep) evolutions can be explained by the photosphere emission model alone needs further discussion. In this work, we investigate in detail the time-resolved spectra and Ep evolutions of photospheric emission from a structured jet, with an inner-constant and outer-decreasing angular Lorentz factor profile. Also, a continuous wind with a time-dependent wind luminosity has been considered. We show that the photosphere spectrum near the peak luminosity is similar to the cutoff power-law spectrum. The spectrum can have the observed average low-energy spectral index α ∼ −1, and the distribution of the low-energy spectral index in our photosphere model is similar to that observed (−2 ≲ α ≲ 0). Furthermore, the two kinds of spectral evolutions during the decay phase, separated by the width of the core (θc), are consistent with the time-resolved spectral analysis results of several Fermi multi-pulse GRBs and single-pulse GRBs, respectively. Also, for this photosphere model we can reproduce the two kinds of observed Ep evolution patterns rather well. Thus, by considering the photospheric emission from a structured jet, we reproduce the observations well for the GRBs best fitted by the cutoff power-law model for the peak-flux spectrum or the time-integrated spectrum.
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