A Reverse Shock and Unusual Radio Properties in GRB 160625B
A Reverse Shock and Unusual Radio Properties in GRB 160625B
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DOI：
10.3847/1538-4357/aa8a76
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发表时间：
2017-05
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影响因子：
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通讯作者：
K. Alexander;T. Laskar;E. Berger;C. Guidorzi;S. Dichiara;W. Fong;A. Gomboc;S. Kobayashi;D. Kopač;C. Mundell;N. Tanvir;P. G. Williams
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作者：
K. Alexander;T. Laskar;E. Berger;C. Guidorzi;S. Dichiara;W. Fong;A. Gomboc;S. Kobayashi;D. Kopač;C. Mundell;N. Tanvir;P. G. Williams
我们给出了异常明亮的长γ射线暴GRB160625B的多波长观测和模拟结果。光学和X射线数据很好地由准直爆轰波的同步辐射所拟合，该准直爆轰波具有ERG的开口角和动能，传播到均匀轮廓的低密度(cm−3)介质中。前向激波在射电频段中占次要地位；相反，射电辐射由两个附加分量主导。第一个分量与反向激波的发射相一致，表明初始洛伦兹因子为，抛射磁化强度为。第二个分量表现出特殊的光谱和时间演化，很可能是湍流的银河系星际介质(ISM)散射射电辐射的结果。这种散射在任何足够致密的河外源中都是预期的，以前在伽玛暴中也见过，但这里看到的大幅度和长持续时间的变化在性质上更类似于以前在类星体中观察到的极端散射事件，而不是正常的星际闪烁效应。需要对未来伽玛暴进行高频率、宽带的射电观测，以充分描述这种影响，这可以灵敏地探测ISM的性质，在正确解释伽玛暴固有的可变性之前，必须考虑到这一点。
We present multi-wavelength observations and modeling of the exceptionally bright long γ-ray burst GRB 160625B. The optical and X-ray data are well fit by synchrotron emission from a collimated blastwave with an opening angle of and kinetic energy of erg, propagating into a low-density ( cm−3) medium with a uniform profile. The forward shock is sub-dominant in the radio band; instead, the radio emission is dominated by two additional components. The first component is consistent with emission from a reverse shock, indicating an initial Lorentz factor of and an ejecta magnetization of . The second component exhibits peculiar spectral and temporal evolution and is most likely the result of scattering of the radio emission by the turbulent Milky Way interstellar medium (ISM). Such scattering is expected in any sufficiently compact extragalactic source and has been seen in GRBs before, but the large amplitude and long duration of the variability seen here are qualitatively more similar to extreme scattering events previously observed in quasars, rather than normal interstellar scintillation effects. High-cadence, broadband radio observations of future GRBs are needed to fully characterize such effects, which can sensitively probe the properties of the ISM and must be taken into account before variability intrinsic to the GRB can be interpreted correctly.