GRB 260226A瞬时辐射中存在一个亚GeV处峰值的额外硬谱成分
An extra hard spectral component peaking at sub-GeV in the prompt emission of GRB 260226A
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中文总结 AI 辅助
本研究通过GBM-LAT联合分析发现GRB 260226A存在亚GeV额外硬成分，早期用截止幂律模型拟合、后期用断裂幂律模型，其峰值比无法用单区SSC解释，双区模型或可说明。
中文摘要 AI 辅助
长期以来，伽马射线暴（GRBs）的瞬时辐射谱在keV至MeV能段一直通过Band函数进行经验描述，而费米卫星（Fermi）的LAT探测器观测到的多个GRB则显示出在更高能段存在额外硬成分的证据。本研究对罕见的LAT触发型GRB 260226A开展了GBM-LAT联合分析，发现其存在一个亚GeV的额外成分。在时变谱分析中，早期阶段截止幂律模型对该额外成分的谱数据拟合效果优于其他模型，而后期阶段则更适合用断裂幂律模型（或至少拟合效果相当）。将早期截止解释为γγ吸收效应意味着，早期的洛伦兹因子较低且随时间增加。该额外成分峰值与Band成分峰值的低比值，难以用单区同步自康普顿（SSC）场景解释，而双区辐射模型（如内激波加速的相对论电子对光球辐射的外逆康普顿散射）可能提供合理的解释。
英文摘要
The prompt emission spectra of gamma-ray bursts (GRBs) have long been empirically described by the Band function over the keV--MeV range, whereas several \textit{Fermi}/LAT-detected GRBs show evidence for an extra hard component at higher energies. Here we present a joint GBM--LAT study of GRB~260226A, a rare LAT seeded onboard trigger GRB, and find that an extra sub-GeV component is present. In the time-resolved analysis, we find that a cutoff power-law model fits the spectral data of the extra component better than other models at earlier times, while at later times, the broken power-law model is preferred (or at least equally good). Interpreting the early cutoff as the $γγ$ absorption implies that the Lorentz factor at early time is lower and increases with time. The low ratio between the peak energy of the extra component and that of the Band component is difficult to explain with a one-zone synchrotron self-Compton (SSC) scenario. Two-zone emission models, such as external inverse Compton scattering of the photosphere emission by relativistic electrons accelerated in internal shocks, could provide a possible explanation.
