标题： 喷流伽马暴的离轴MeV和甚高能伽马射线发射 显示英文标题

标题： Off-axis MeV and very-high-energy gamma-ray emissions from structured gamma-ray burst jets

摘要： 高能（VHE）光子在TeV能区来自伽马射线暴（GRB）喷流的光子，在多信使时代将发挥重要作用，其中相当一部分事件是从喷流的侧面观测到的。 我们表明，对于侧面观测者来说，即使发射半径相同，不同能量的光子（尤其是MeV和TeV光子）也会来自不同的发射区域。发射区的位置取决于表面亮度的喷流结构，而这些结构在不同能量下通常是不同的，这主要是由于VHE光子通过电子-正电子对产生过程的衰减所致。 这种侧面偏移效应并不支持通常的一区近似，并且会产生与GRB持续时间相当的时间延迟，这对于未来的VHE观测（例如切伦科夫望远镜阵列）至关重要。 显示英文摘要

摘要： Very-high-energy (VHE) photons around TeV energies from a gamma-ray burst (GRB) jet will play an essential role in the multi-messenger era, with a fair fraction of the events being observed off-axis to the jet. We show that different energy photons (MeV and TeV photons in particular) arrive from different emission zones for off-axis observers even if the emission radius is the same. The location of the emission region depends on the jet structure of the surface brightness, and the structures are generally different at different energies, mainly due to the attenuation of VHE photons by electron-positron pair creation. This off-axis zone-shift effect does not justify the usual one-zone approximation and also produces a time-delay of VHE photons comparable to the GRB duration, which is crucial for future VHE observations, such as by the Cherenkov Telescope Array.