论文标题
Fermi大面积望远镜从超长的伽马射线爆发中检测GEV排放
Detection of GeV emission from an ultra-long gamma-ray burst with the Fermi Large Area Telescope
论文作者
论文摘要
Fermi Gamma-ray爆发监视器（GBM）检测到的GRB 220627A显示了两集的伽马射线发射，它们被{$ \ sim $ 700}的长静态阶段隔开。由于两个情节中的类似时间形状和光谱，GRB 220627A被推测为重力镜头伽马射线爆发（GRB）。我们分析了费米大面积望远镜（LAT）数据，发现在第一集中，大约49个伽马射线光子来自GRB，而第二集中没有100 MEV的光子。基于这两个事件的宽带光谱研究，可以在高置信度上排除重力镜头方案，因此我们得出结论，GRB 220627A是一种本质上具有超大的GRB，迅速的爆发持续时间持续时间超过1000 s。然后是第一种从超大GRB中检测到GEV发射的情况。我们发现，在LAT光曲线中看到的短尖峰也存在于GBM探测器中，该探测器看到了爆发，这表明整个费米能范围内的发射范围很常见。在早期及时阶段，检测15.7 GEV光子的下限在GRB弹出的批量Lorentz系数上的下限为$γ\ ge300 $。大量洛伦兹因子的限制可能会揭示超大GRB的起源。
GRB 220627A, detected by Fermi Gamma-ray Burst Monitor (GBM), shows two episodes of gamma-ray emission, which are separated by a {$\sim$700} s long quiescent phase. Due to similar temporal shapes and spectra in the two episodes, GRB 220627A is speculated to be a gravitationally lensed gamma-ray burst (GRB). We analyze the Fermi Large Area Telescope (LAT) data and find that about 49 gamma-ray photons above 100 MeV come from the GRB during the first episode, while there are no photons above 100 MeV in the second episode. Based on the broadband spectral study of the two episodes, the gravitationally lensing scenario can be ruled out at a high confidence level and we thus conclude that GRB 220627A is an intrinsically ultralong GRB with the prompt burst emission lasting longer than 1000 s. It is then the first case that GeV emission is detected from an ultralong GRB. We find that a short spike seen in the LAT light curve is also present in GBM detectors that see the burst, suggesting a common internal region of emission across the entire Fermi energy range. The detection of a 15.7 GeV photon during the early prompt phase places a lower limit of $Γ\ge300$ on the bulk Lorentz factor of the GRB ejecta. The constraint on the bulk Lorentz factor could shed light on the origin of ultralong GRBs.
