伽马射线暴中的高能与甚高能X射线耀斑
X-ray Flares in Gamma-Ray Bursts at High and Very-High-Energies
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中文总结 AI 辅助
本研究系统分析47个GRB的66个X射线耀斑，发现仅5个有显著高能发射，约束其发射区域高度磁化，预测晚期X射线耀斑的甚高能伽马射线发射具探测潜力。
中文摘要 AI 辅助
Swift X射线望远镜发现，很大一部分伽马射线暴（GRB）的早期余辉会出现快速且明亮的X射线耀斑，其快速时间变异性与光谱演化表明它们可能起源于类似瞬时MeV辐射的内部激波，但物理起源与辐射机制仍存在争议。高能（>100 MeV）和甚高能（>30 GeV）伽马射线观测是探测耀斑耗散区域的有力工具，可在光学薄相对论喷流的同步自康普顿场景下约束其大小、磁场强度及粒子加速过程。我们对17年间X射线望远镜观测到的47个GRB的66个X射线耀斑开展了系统多波段研究，所有耀斑均位于费米大面积望远镜（Fermi LAT）的视场内，探究了它们的GeV对应体，发现仅有5个耀斑表现出显著的高能发射（>3σ）。宽带光谱建模表明，该GeV发射与标准前向激波余辉一致。我们进一步探究了耀斑光谱特性与1 keV、10 keV及1 GeV处能流的相关性，利用同步自康普顿模型约束了发射区域的物理条件，包括磁场强度、体洛伦兹因子及发射半径。对于最严格的GeV上限，我们发现磁场与电子光度比≥1，意味着发射区域高度磁化。我们预测了X射线耀斑在早期（~500秒）和晚期（~5000秒）的甚高能伽马射线发射，并评估了切伦科夫望远镜的探测能力，发现晚期X射线耀斑因观测可达性提升、灵敏度提高及切伦科夫望远镜阵列天文台等设施的响应时间约束降低，是后续观测最具前景的目标。
英文摘要
A significant fraction of GRB early afterglows exhibit fast and bright X-ray flares, discovered by Swift X-ray Telescope. Their rapid temporal variability and spectral evolution have suggested an internal shock origin, analogous to prompt MeV emission. However, their physical origin and radiation mechanism remain debated. High-energy (> 100 MeV) and very-high-energy (> 30 GeV) gamma-ray observations provide a powerful probe of flare dissipation region, constraining its size, magnetic field strength, and particle acceleration under the synchrotron self-Compton scenario in optically thin relativistic jets. We present a systematic multi-wavelength study of 66 X-ray flares from 47 GRBs observed by X-ray Telescope over 17 years, all within field of view of Fermi Large Area Telescope. We investigate their GeV counterparts and find that only five flares exhibit significant high-energy emission (> 3 sigma). Broadband spectral modeling indicates that this GeV emission is consistent with standard forward shock afterglow. We further investigate correlations between flare spectral properties and energy fluxes at 1 keV, 10 keV, and 1 GeV. Using a synchrotron self-Compton model, we constrain the physical conditions of the emitting region, including magnetic field strength, bulk Lorentz factor, and emission radius. For the most stringent GeV upper limits, we find a magnetic-to-electron luminosity ratio greater than or equal to 1, implying a highly magnetized emitting region. We predict very-high-energy gamma-ray emission from X-ray flares at early (~500s) and late (~5000s) times and assess their detectability with Cherenkov Telescopes. We find that later X-ray flares provide the most promising targets for follow-up observations owing to improved observational accessibility, sensitivity, and reduced response-time constraints of facilities such as Cherenkov Telescope Array Observatory.
发表机构
- Gran Sasso Science Institute (GSSI)（格兰萨索科学研究所）
- INFN - Laboratori Nazionali del Gran Sasso（意大利国家核物理研究所-格兰萨索国家实验室）
- INAF - Osservatorio Astronomico d’Abruzzo（意大利国家天体物理研究所-阿布鲁佐天文台）
- INAF - Osservatorio Astronomico di Brera（意大利国家天体物理研究所-布雷拉天文台）
- Institute of Space Sciences (ICE), CSIC（空间科学研究所（ICE），西班牙高等科学研究委员会）
- Institut d’Estudis Espacials de Catalunya (IEEC)（加泰罗尼亚空间研究研究所（IEEC））
- Department of Astrophysics/IMAPP, Radboud University（拉德堡德大学天体物理学/IMAPP系）
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