GRB jet structure and the jet break
GRB jet structure and the jet break
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DOI：
10.1093/mnras/stab2071
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发表时间：
2021-04
影响因子：
4.8
通讯作者：
G. Lamb;D. A. Kann;J. Fern'andez;I. Mandel;A. Levan;N. Tanvir
中科院分区：
文献类型：
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作者：
G. Lamb;D. A. Kann;J. Fern'andez;I. Mandel;A. Levan;N. Tanvir
本文研究了束内伽玛射线暴（GRB）光学余辉中不同横向喷流结构剖面的喷流破裂形状。我们考虑有和没有横向扩展以及喷流核心半张开角θc内的一系列倾角的情况。我们拟合模型和观察到的余辉光变曲线与一个光滑破碎的幂律函数与一个自由参数κ，描述了中断的锐度。我们发现，喷流中断是尖锐的（κ是更大的）时，包括横向扩展比在没有横向扩展。对于具有锐边核心的轮廓，锐度参数的范围很宽，为0.1 κ 4.6，而当包括有和没有横向扩展的模型时，具有光滑边缘核心的轮廓的范围较窄，为0.1 κ 2.2。对于锐边喷流，喷流破碎的尖锐程度强烈依赖于θc内系统的倾角，而对于光滑边喷流，κ更强烈地依赖于θc的大小。使用20个伽玛暴的样本，我们发现9个候选的光滑边缘喷流结构和8个候选的尖锐边缘喷流结构，而其余3个是一致的。由锐度参数κ测量的喷流破裂的形状可以用作束内GRB中横向结构存在的初始检查，其中余辉在喷流破裂时间处和附近被良好地采样。
We investigate the shape of the jet break in within-beam gamma-ray burst (GRB) optical afterglows for various lateral jet structure profiles. We consider cases with and without lateral spreading and a range of inclinations within the jet core half-opening angle, θc. We fit model and observed afterglow light curves with a smoothly-broken power-law function with a free-parameter κ that describes the sharpness of the break. We find that the jet break is sharper (κ is greater) when lateral spreading is included than in the absence of lateral spreading. For profiles with a sharp-edged core, the sharpness parameter has a broad range of 0.1 ≲ κ ≲ 4.6, whereas profiles with a smooth-edged core have a narrower range of 0.1 ≲ κ ≲ 2.2 when models both with and without lateral spreading are included. For sharp-edged jets, the jet break sharpness depends strongly on the inclination of the system within θc, whereas for smooth-edged jets, κ is more strongly dependent on the size of θc. Using a sample of 20 GRBs, we find 9 candidate smooth-edged jet structures and 8 candidate sharp-edged jet structures, while the remaining 3 are consistent with either. The shape of the jet break, as measured by the sharpness parameter κ, can be used as an initial check for the presence of lateral structure in within-beam GRBs where the afterglow is well-sampled at and around the jet-break time.