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arXiv 2311.01705astro-ph.HE
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离轴余辉闭包关系与 Fermi-LAT 探测到的伽马射线暴

Off-axis Afterglow Closure Relations and Fermi-LAT Detected Gamma-Ray Bursts

Nissim Fraija, M. G. Dainotti, D. Levine, B. Betancourt Kamenetskaia, A. Galvan-Gamez

AI总结:

本文将 SSC 余辉闭包关系从轴上喷流扩展到离轴情形,并结合能量注入与电子谱指数分析 Fermi-LAT 2FLGC 高能暴,识别同步与 SSC 辐射最可能的介质环境。

摘要:

伽马射线暴(GRBs)是在极端条件下研究多波段观测最有前景的暂现事件之一。对来自暴的 GeV 光子的观测将提供关于 GRB 物理的关键信息,包括离轴辐射。Fermi 大面积望远镜(Fermi-LAT)合作组发布了第二版伽马射线暴目录(2FLGC)。该目录包含29个光子能量高于10 GeV的暴。尽管同步辐射前激波模型已经很好地解释了 GRBs 的余辉数据,但能量大于10 GeV的光子很难在这一框架内得到解释。为研究2FLGC中所述这些暴的谱指数和时间指数,Fraija 等人(2022a)提出了由在星风介质和恒密度介质中减速的轴上喷流所发射的同步自康普顿(SSC)的闭包关系(CRs)。在本文中,我们将 SSC 余辉的 CRs 从轴上情形扩展到离轴情形,包括看似离轴的同步余辉辐射。为了研究2FLGC所报告的这些暴的谱指数和时间指数演化,我们针对谱指数为 $1<p<2$ 和 $2<p$ 的电子分布,考虑了绝热和辐射 regime 下具有能量注入的流体动力学演化。结果表明,无论是否存在能量注入,同步辐射最可能的情形都对应于星风;而 SSC 辐射最可能的情形在没有能量注入时对应于恒密度,在有能量注入时对应于星风。

英文摘要:

Gamma-ray bursts (GRBs) are one of the most promising transient events for studying multi-wavelength observations in extreme conditions. Observation of GeV photons from bursts would provide crucial information on GRB physics, including the off-axis emission. The Second Gamma-ray Burst Catalog (2FLGC) was announced by the Fermi Large Area Telescope (Fermi-LAT) Collaboration. This catalog includes 29 bursts with photon energy higher than 10 GeV. While the synchrotron forward-shock model has well explained the afterglow data of GRBs, photon energies greater than 10 GeV are very difficult to interpret within this framework. To study the spectral and temporal indices of those bursts described in 2FLGC, Fraija et al. (2022a) proposed the closure relations (CRs) of the synchrotron self-Compton (SSC) emitted from an on-axis jet which decelerates in stellar-wind and the constant-density medium. In this paper, we extend the CRs of the SSC afterglow from an on-axis scenario to an off-axis, including the synchrotron afterglow radiation that seems off-axis. In order to investigate the spectral and temporal index evolution of those bursts reported in 2FLGC, we consider the hydrodynamical evolution with energy injection in the adiabatic and radiative regime for an electron distribution with a spectral index of $1<p<2$ and $2 < p$. The results show that the most likely scenario for synchrotron emission corresponds to the stellar wind whether or not there is energy injection and that the most likely scenario for SSC emission corresponds to the constant density when there is no energy injection and to the stellar wind when there is energy injection.

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