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arXiv 2502.13435astro-ph.HE
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超长伽马射线暴220627A的无线电余辉

The radio afterglow of the ultra-long GRB 220627A

University of Toronto(多伦多大学);The Hebrew University of Jerusalem(耶路撒冷希伯来大学);The University of Sydney(悉尼大学);Curtin University(科廷大学);Swinburne University of Technology(斯威本科技大学);University of Wisconsin-Milwaukee(威斯康星大学密尔沃基分校);European University Cyprus(塞浦路斯欧洲大学);University of Oxford(牛津大学)
James K. Leung, Om Sharan Salafia, Cristiana Spingola, Giancarlo Ghirlanda, Stefano Giarratana, Marcello Giroletti, Cormac Reynolds, Ziteng Wang, Tao An, Adam D… 展开作者

James K. Leung, Om Sharan Salafia, Cristiana Spingola, Giancarlo Ghirlanda, Stefano Giarratana, Marcello Giroletti, Cormac Reynolds, Ziteng Wang, Tao An, Adam Deller, Maria R. Drout, David L. Kaplan, Emil Lenc, Tara Murphy, Miguel Perez-Torres, Lauren Rhodes

AI总结:

研究发现超远超长GRB 220627A的无线电余辉,通过分析其光变曲线和光谱排除透镜效应,提出三种可能的解释并测试透镜假说。

摘要:

我们报告了迄今为止发现的最远超长伽马射线暴(GRB)GRB~220627A的无线电余辉,其红移为$z=3.084$。其早期伽马射线光变曲线显示双脉冲特征,两个脉冲之间间隔一个持续约15分钟的宁静期,导致早期推测它可能是强引力透镜GRB。然而,我们分析了在两个脉冲时间间隔内获取的\textit{Fermi}/GBM光谱,发现其能谱分布有明显差异,排除了透镜情景。我们从爆发后7天到456天观测到无线电余辉:初始阶段呈陡降($F_ν \propto t^{-2}$),随后在约20天后出现较缓的下降($F_ν \propto t^{-1/2}$)。有三种情景可以解释这些无线电特性:(i)来自额外缓慢喷射物的能量注入,追上外部冲击波;(ii)密度分布呈$ n \propto r^{-8/3} $;或者(iii)存在一个慢而宽的喷射物以及一个快而窄的喷射物。我们还通过甚长基线干涉仪(VLBI)观测进行了独立的透镜假说测试,在爆发后约12天通过首次寻找候选透镜GRB余辉的多重图像来检验。我们的实验突显了在时间关键的VLBI实验中发展实时相关能力的日益增长的需求,特别是随着我们向SKA和ngVLA时代的射电天文学迈进。

英文摘要:

We present the discovery of the radio afterglow of the most distant ultra-long gamma-ray burst (GRB) detected to date, GRB~220627A at redshift $z=3.084$. Its prompt gamma-ray light curve shows a double-pulse profile, with the pulses separated by a period of quiescence lasting ${\sim} 15$\,min, leading to early speculation it could be a strongly gravitationally lensed GRB. However, our analysis of the \textit{Fermi}/GBM spectra taken during the time intervals of both pulses show clear differences in their spectral energy distributions, disfavouring the lensing scenario. We observed the radio afterglow from 7 to 456\,d post-burst: an initial, steep decay ($F_ν \propto t^{-2}$) is followed by a shallower decline ($F_ν \propto t^{-1/2}$) after ${\sim} 20$\,d. There are three scenarios that could explain these radio properties: (i) energy injection from an additional, slower ejecta component catching up to the external shock; (ii) a stratified density profile going as $n \propto r^{-8/3}$; or alternatively, (iii) the presence of a slow, wide ejecta component in addition to a fast, narrow ejecta component. We also conducted an independent test of the lensing hypothesis via Very Long Baseline Interferometry (VLBI) observations at ${\sim} 12$\,d post-burst by searching, for the first time, for multiple images of the candidate lensed GRB afterglow. Our experiment highlighted the growing need for developments in real-time correlation capabilities for time-critical VLBI experiments, particularly as we advance towards the SKA and ngVLA era of radio astronomy.

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