The ultra-long GRB 220627A at z = 3.08
The ultra-long GRB 220627A at z = 3.08
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z = 3.08 处的超长 GRB 220627A
DOI：
10.1051/0004-6361/202347017
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发表时间：
2023
影响因子：
6.5
通讯作者：
De Wet S
中科院分区：
文献类型：
--
作者：
De Wet S
背景伽马射线暴220627A是一次罕见的爆发，有两次明显的γ射线发射事件，间隔了近1000次S，两次触发了费米伽马射线爆发监测器。费米大区望远镜探测到的高能GeV发射与第一次发射事件一致，但与第二次发射事件不一致。MeerLICHT光余辉的发现导致缪斯观测，确保了爆发红移为z= 3.08，这是迄今为止探测到的最远的超长伽马射线暴。目的文献中提出了一些超长伽马射线暴的祖先与正常长伽马射线暴不同。我们的目的是确定伽玛暴220627A的余辉和主体性质是否符合这种解释。方法我们对外部前向激波框架内的余辉数据进行了经验和理论模拟，并通过模拟缪斯光谱中的吸收线来确定伽玛暴环境的金属丰度。结果我们的光学数据表明，在∼1.2d，光曲线上有喷流破裂的证据，而我们的理论模拟表明，我们的理论模型更倾向于均匀的环暴介质。我们的正激波参数对于更广泛的伽玛暴群体来说是典型的，我们发现爆发的环境是以亚太阳金属为特征的。结论我们对伽玛暴220627A的观测和模拟表明，与正常长伽玛暴的前驱相比，并不需要不同的前驱。我们发现，需要对超长伽玛暴进行更多的观测，以确定它们是否形成了一个独立的群体，具有明显的即时和余辉特征，可能还有不同的前身。
ContextGRB 220627A is a rare burst with two distinctγ-ray emission episodes separated by almost 1000 s that triggered theFermiGamma-ray Burst Monitor twice. High-energy GeV emission was detected by theFermiLarge Area Telescope coincident with the first emission episode but not the second. The discovery of the optical afterglow with MeerLICHT led to MUSE observations which secured the burst redshift toz= 3.08, making this the most distant ultra-long gamma-ray burst (GRB) detected to date.AimsThe progenitors of some ultra-long GRBs have been suggested in the literature to be different to those of normal long GRBs. Our aim is to determine whether the afterglow and host properties of GRB 220627A agree with this interpretation.MethodsWe performed empirical and theoretical modelling of the afterglow data within the external forward shock framework, and determined the metallicity of the GRB environment through modelling the absorption lines in the MUSE spectrum.ResultsOur optical data show evidence for a jet break in the light curve at ∼1.2 days, while our theoretical modelling shows a preference for a homogeneous circumburst medium. Our forward shock parameters are typical for the wider GRB population, and we find that the environment of the burst is characterised by a sub-solar metallicity.ConclusionsOur observations and modelling of GRB 220627A do not suggest that a different progenitor compared to the progenitor of normal long GRBs is required. We find that more observations of ultra-long GRBs are needed to determine if they form a separate population with distinct prompt and afterglow features, and possibly distinct progenitors.