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arXiv 2005.03710astro-ph.HE
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伽马射线暴余辉的多波段同步辐射偏振

Multi-Wave band Synchrotron Polarization of Gamma-Ray Burst Afterglows

Jiro Shimoda, Kenji Toma

摘要:

假设前向激波下游存在相干长度为等离子体趋肤深度尺度的各向异性湍流磁场,研究了伽马射线暴(GRB)余辉的多波段同步辐射线偏振。我们发现,对于典型的伽玛暴,在比较的光学偏振,射电偏振度显示了类似的时间演变,但一个显着较小的峰值。这是由于在无线电和光学波段之间观察到的强度图像形状的差异。我们还表明,偏振光谱的程度经历了从低到高偏振制度以上的光谱峰值频率的强度逐渐变化,并且在两个制度中的偏振角的差异是零或90度。因此,多波段同步观测伽玛暴余辉将是等离子体尺度磁场模型的一个新的确定性检验。我们还讨论了最近用ALMA和其他磁场组态模型对GRB 171205 A射电线性极化探测的理论意义。

英文摘要:

Multi-wave band synchrotron linear polarization of gamma-ray burst (GRB) afterglows is studied under the assumption of an anisotropic turbulent magnetic field with a coherence length of the plasma skin-depth scale in the downstream of forward shocks. We find that for typical GRBs, in comparison to the optical polarization, the degree of radio polarization shows a similar temporal evolution but a significantly smaller peak value. This results from differences in observed intensity image shapes between the radio and optical bands. We also show that the degree of the polarization spectrum undergoes a gradual variation from the low- to the high-polarization regime above the intensity of the spectral peak frequency, and that the difference in polarization angles in the two regimes is zero or 90 degrees. Thus, simultaneous multi-wave band polarimetric observations of GRB afterglows would be a new determinative test of the plasma-scale magnetic field model. We also discuss theoretical implications from the recent detection of radio linear polarization in GRB 171205A with ALMA and other models of magnetic field configuration.

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