KLEIN–NISHINA EFFECTS ON THE HIGH-ENERGY AFTERGLOW EMISSION OF GAMMA-RAY BURSTS
KLEIN–NISHINA EFFECTS ON THE HIGH-ENERGY AFTERGLOW EMISSION OF GAMMA-RAY BURSTS
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DOI：
10.1088/0004-637x/712/2/1232
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发表时间：
2009-11
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影响因子：
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通讯作者：
Xiang-Yu Wang;Hao-Ning He;Zhuo Li;Xuefeng Wu;Z. Dai
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作者：
Xiang-Yu Wang;Hao-Ning He;Zhuo Li;Xuefeng Wu;Z. Dai
费米大面积射电望远镜（LAT）最近在多个伽玛暴（GRB）中探测到了持续时间远大于亚MeV瞬发的高能（~ 100 MeV）扩展伽玛射线辐射。一种可能的情况是，这种发射是由在前向冲击中加速的电子产生的余辉同步辐射。在这种情况下，产生同步高能辐射的电子也会经历逆康普顿（IC）损耗，并且与同步光子的IC散射应该处于克莱因-西名（KN）状态。本文研究了KN散射对高能同步辐射余辉辐射的影响。我们发现，在早期的KN抑制效应对那些产生高能量发射的电子通常是强的，因此它们的IC损失是小的，康普顿参数Y在很宽的参数空间范围内是几个。这导致了一个相对明亮的高能量同步余辉，可以检测到费米-LAT。随着KN抑制效应随时间的减弱，IC损失增加，并可能在某些参数空间中占主导地位。这将导致高能同步辐射的时间衰减比标准同步辐射模型预测的更快，这可以解释在GRB 090510和GRB 090902 B中观察到的早期高能伽马射线辐射的快速衰减。
Extended high-energy (≳100 MeV) gamma-ray emission that lasts much longer than the prompt sub-MeV emission has been detected from quite a few gamma-ray bursts (GRBs) by Fermi–Large Area Telescope (LAT) recently. A plausible scenario is that this emission is the afterglow synchrotron emission produced by electrons accelerated in the forward shocks. In this scenario, the electrons that produce synchrotron high-energy emission also undergo inverse Compton (IC) loss and the IC scattering with the synchrotron photons should be in the Klein–Nishina (KN) regime. Here we study effects of the KN scattering on the high-energy synchrotron afterglow emission. We find that at early times the KN suppression effect on those electrons that produce the high-energy emission is usually strong and therefore their IC loss is small with a Compton parameter Y ≲ a few for a wide range of parameter space. This leads to a relatively bright synchrotron afterglow at high energies that can be detected by Fermi–LAT. As the KN suppression effect weakens with time, the IC loss increases and could dominate over the synchrotron loss in some parameter spaces. This will lead to a faster temporal decay of the high-energy synchrotron emission than is predicted by the standard synchrotron model, which may explain the observed rapid decay of the early high-energy gamma-ray emission in GRB090510 and GRB090902B.