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arXiv 2501.09093astro-ph.HE
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使用动力学方法研究结构化GRB喷流的TeV余辉辐射

TeV afterglow emission from a structured GRB jet using the kinetic approach

John P. Hope, Hendrik J. van Eerten, Sayan Kundu, Patricia Schady

AI总结:

本文使用动力学方法研究结构化GRB喷流结构对TeV余辉辐射的影响,通过改进katu代码自洽处理IC冷却,发现能量随角度衰减更快的喷流IC峰值通量降低,并重现了GRB 170817A光变曲线。

摘要:

近年来,伽马射线暴余辉中TeV辐射的探测样本不断增加,结构化喷流在余辉建模中的作用也日益重要。使用动力学方法,我们证明了余辉喷流的结构会影响其TeV辐射:能量随角度衰减更快的喷流,其逆康普顿(IC)峰值通量相对于同步辐射峰值通量有所降低。我们使用了修改版的katu代码,为其加入了绝热膨胀,并对电子和光子群体进行了完全自洽的IC冷却处理。我们将结果与半解析代码afterglowpy进行了比较,发现除了在偏离轴线的早期阶段(此时重子负载效应较为重要)外,两者具有良好的一致性。我们对比了无IC冷却、Thomson冷却以及包含Klein-Nishina效应三种情况下的电子冷却,发现只有在康普顿势显著增加时,光谱才能被区分开来。我们获得了与半解析解相似的冷却率,仅在IC主导冷却向同步辐射主导冷却的过渡阶段存在微小差异。最后,我们使用由afterglowpy确定并为我们的模型重新缩放的最佳拟合参数,重现了GRB 170817A的光变曲线。对于我们选择的参数,我们发现如果GRB 170817在轴观测,即使使用即将建成的Cherenkov Telescope Array Observatory,也无法在TeV能段探测到它。

英文摘要:

Recent years have seen a growing sample of TeV emission detections in gamma-ray burst afterglows, as well as an increasing role for structured jets in afterglow modelling. Using a kinetic approach, we show that the structure of an afterglow jet impacts its TeV emission, with jets where the energy falls off more sharply with angle showing a decrease in Inverse Compton (IC) peak flux relative to synchrotron peak flux. We use a modified version of the code katu, to which we have added adiabatic expansion and a fully self-consistent treatment of IC cooling both for the electron and photon populations. We compare our results to the semi-analytical code afterglowpy, finding a good agreement with our model except at early times off axis where the effects of baryon loading are important. We compare electron cooling in the cases where there is no IC cooling, Thomson cooling and an inclusion of Klein-Nishina effects, finding that the spectra can only be distinguished if the Compton potential is significantly increased. We obtain a similar cooling rate compared to semi-analytical solutions, with some small difference at the transition from IC to synchrotron dominated cooling. Finally, we use best-fit parameters determined by afterglowpy and re-scaled for our model to reproduce the light curves of GRB 170817A. For our choice of parameters, we find that GRB 170817 would not have been detected in the TeV domain if seen on-axis, even by the upcoming Cherenkov Telescope Array Observatory.

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