High-Energy Photon Emission in the Early Afterglow of GRBs
High-Energy Photon Emission in the Early Afterglow of GRBs
复制标题
伽玛暴早期余辉中的高能光子发射
DOI：
10.1086/468175
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
E. Waxman
中科院分区：
文献类型：
--
作者：
A. Pe’er;E. Waxman
我们考虑了在火球模型框架内，由于与周围介质的相互作用，在一分钟的时间尺度上，火球减速开始时，非常高能量的~1GeV到~1TeV光子的发射。我们的含时数值模型包括电子同步辐射的精确处理，逆康普顿散射，对产生，以及电磁级联的演化(由对产生或介子的光产生启动)。我们发现：(1)1-10GeV通量对模型参数不敏感，对于z=1爆发，通量为~10~(-7)ergs cm~(-2)S~(-1)，完全在GLAST的探测能力之内。(2)次TeV通量与周围介质密度和磁场携带的热能分数ϵB有关，在典型ϵ密度和≲B为10-4时为~10-7ergs cm-2 S-1，在有风和ϵB~10-0.5时为10-10ergs cm-2 S-1。(3)Hess、Magic、Milagro和VERITAS等高能γ-射线实验都能探测到亚TeV通量。(4)结合~1keV、~1GeV和次TeV观测，可以同时确定ϵB和环境介质密度。(5)谱对加速电子能量分布的谱指数只有微弱的依赖关系。介子的产生高能质子的能量损失在风的情况下可能对高能光子的光度有很大贡献。然而，在这种情况下，很难区分电子和质子的贡献，因为光谱形状主要由对产生光学厚度的能量依赖性决定。
We consider the emission within the fireball model framework of very high energy, ~1 GeV to >1 TeV photons, on a minute timescale, during the onset of fireball deceleration due to interaction with surrounding medium. Our time-dependent numerical model includes exact treatment of electron synchrotron emission, inverse Compton scattering, pair production, and evolution of electromagnetic cascades (initiated by pair production or photoproduction of pions). We find the following: (1) The 1-10 GeV flux is not sensitive to model parameters and is ~10-7 ergs cm-2 s-1 for z = 1 bursts, well within the detection capabilities of GLAST. (2) The sub-TeV flux depends on the surrounding medium density and on the fraction of thermal energy carried by the magnetic field, ϵB. It ranges from ~10-7 ergs cm-2 s-1 in the case of typical ISM density and ϵB ≲ 10-4, to 10-10 ergs cm-2 s-1 in the case of a source surrounded by a wind and ϵB ~ 10-0.5. (3) The sub-TeV flux is detectable by high-energy γ-ray experiments such as HESS, MAGIC, Milagro, and VERITAS. (4) Combined ~1 keV, ~1 GeV, and sub-TeV observations will allow determination of both ϵB and the ambient medium density. (5) The spectra depend only weakly on the spectral index of the energy distribution of the accelerated electrons. Pion production energy loss of high-energy protons may contribute significantly in the wind case to the luminosity of high-energy photons. However, it is difficult to distinguish in this case between the electron and proton contributions, since the spectral shape is determined primarily by the energy dependence of the pair production optical depth.