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arXiv 1808.00636astro-ph.HE
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费米伽马射线暴数据的综合分析:IV。光谱滞后及其与Ep演化的关系

A comprehensive analysis of Fermi Gamma-Ray Burst Data: IV. Spectral lag and Its Relation to Ep Evolution

Rui-Jing Lu, Yun-Feng Liang, Da-Bin Lin, Jing Lv, Xiang-Gao Wang, Hou-Jun Lv, Hong-Bang Liu, En-Wei Liang, Bing Zhang

摘要:

研究了费米GBM望远镜观测到的84个伽玛暴(GRB)中92个亮脉冲的光谱演化和光谱滞后行为。这些脉冲可以分为硬到软脉冲(H2S,64/92)、H2S主导的跟踪脉冲(21/92)和其他跟踪脉冲(7/92)。我们重点研究了H2S和H2S主导的跟踪脉冲的光谱演化和光谱滞后之间的关系。%,在硬到软脉冲(H2S,64/92)和H2S占主导地位的跟踪(21/92)脉冲。用$\log E_p\propto k_E\log(t+t_0)$(${\hatτ} \propto k_{\hatτ}\log E$)估计光谱演化的主要趋势(滞后行为),其中$E_p$是辐射光谱中的峰值光子能量,$t+t_0$是相对于脉冲$-t_0$开始的观察者时间,而${\hatτ}$是具有能量$E$的光子相对于能带$8$ - $25$ keV的光谱滞后。对于H2S和以H2S为主的跟踪脉冲,发现$k_{\hatτ}/W$和$k_E$之间存在弱相关性,其中$W$是脉冲宽度。我们还研究了30个波形良好的脉冲的谱滞后行为与峰值时间$t_{\rm p_E}$和估计的主要趋势与$\log t_{\rm p_E}\propto k_{t_p}\log E$的谱滞后行为。发现$k_{t_p}$与$k_E$相关。我们进行模拟下的光谱演化的唯象模型,并发现这些相关性再现。然后,我们得出结论,光谱滞后密切相关的脉冲内的光谱演化。对这些观测结果最自然的解释是,发射来自同一流体单元中的电子,发射点远离中心引擎,正如在适度高$σ$流出中调用磁耗散的模型中所预期的那样。

英文摘要:

The spectral evolution and spectral lag behavior of 92 bright pulses from 84 gamma-ray bursts (GRBs) observed by the Fermi GBM telescope are studied. These pulses can be classified into hard-to-soft pulses (H2S, 64/92), H2S-dominated-tracking pulses (21/92), and other tracking pulses (7/92). We focus on the relationship between spectral evolution and spectral lags of H2S and H2S-dominated-tracking pulses. %in hard-to-soft pulses (H2S, 64/92) and H2S-dominating-tracking (21/92) pulses. The main trend of spectral evolution (lag behavior) is estimated with $\log E_p\propto k_E\log(t+t_0)$ (${\hatτ} \propto k_{\hatτ}\log E$), where $E_p$ is the peak photon energy in the radiation spectrum, $t+t_0$ is the observer time relative to the beginning of pulse $-t_0$, and ${\hatτ}$ is the spectral lag of photons with energy $E$ with respect to the energy band $8$-$25$ keV. For H2S and H2S-dominated-tracking pulses, a weak correlation between $k_{\hatτ}/W$ and $k_E$ is found, where $W$ is the pulse width. We also study the spectral lag behavior with peak time $t_{\rm p_E}$ of pulses for 30 well-shaped pulses and estimate the main trend of the spectral lag behavior with $\log t_{\rm p_E}\propto k_{t_p}\log E$. It is found that $k_{t_p}$ is correlated with $k_E$. We perform simulations under a phenomenological model of spectral evolution, and find that these correlations are reproduced. We then conclude that spectral lags are closely related to spectral evolution within the pulse. The most natural explanation of these observations is that the emission is from the electrons in the same fluid unit at an emission site moving away from the central engine, as expected in the models invoking magnetic dissipation in a moderately-high-$σ$ outflow.

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