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arXiv 1003.1265astro-ph.HEastro-ph.CO
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GRB余辉发射是各向异性的吗?

Is GRB afterglow emission intrinsically anisotropic ?

A. M. Beloborodov, F. Daigne, R. Mochkovitch, Z. L. Uhm

摘要:

相对论性冲击波的曲率意味着它的辐射到达观测者时会有时间上的扩展。这种效应被认为可以消除伽玛射线暴余辉光变曲线的快速变化。我们注意到,如果在爆炸波的静止坐标系中发射是各向异性的(即,如果发射是边缘变亮或边缘变暗的),则扩散效应减小。特别是,同步辐射几乎肯定是各向异性的,并且可能是强烈的各向异性,这取决于爆炸波中电子加速的细节。各向异性余辉可以在高频率(高于“快速冷却”频率)下显示快速和强烈的变化。这也许可以解释伽玛暴X射线余辉中奇异特征的存在,例如突然的下降和耀斑。我们还注意到,适度的各向异性可以显着延迟光变曲线中的“喷流中断”,这使得它更难检测。

英文摘要:

The curvature of a relativistic blast wave implies that its emission arrives to observers with a spread in time. This effect is believed to wash out fast variability in the lightcurves of GRB afterglows. We note that the spreading effect is reduced if emission is anisotropic in the rest-frame of the blast wave (i.e. if emission is limb-brightened or limb-darkened). In particular, synchrotron emission is almost certainly anisotropic, and may be strongly anisotropic, depending on details of electron acceleration in the blast wave. Anisotropic afterglows can display fast and strong variability at high frequencies (above the 'fast-cooling' frequency). This may explain the existence of bizarre features in the X-ray afterglows of GRBs, such as sudden drops and flares. We also note that a moderate anisotropy can significantly delay the 'jet break' in the lightcurve, which makes it harder to detect.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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