论文标题
GRB 210702A的快速无线电亮度
Rapid radio brightening of GRB 210702A
论文作者
论文摘要
我们观察到GRB 210702a的快速启动亮度在燃烧后仅11小时，澳大利亚望远镜紧凑型阵列（ATCA），在5小时内的早期无线电变异性在9.0、16.7和21.2GHz的〜15分钟时跟踪早期无线电变异性。损坏的幂律适合9.0GHz光曲线，显示5小时耀斑在爆发后〜13hr时的通量密度达到0.4 +/- 0.1MJY，并急剧上升和下降。在标准的内部冲击模型中不会预期观察到的时间和光谱演化，在较长的时间尺度上，向前和反向电击无线电发射会演变。 Neil Gehrels Swift天文台的早期（<1天）光学和X射线光曲线表现出典型的余波向前冲击行为，使我们能够使用Blast Wave物理学来确定可能均匀的Circumburst培养基和发射的电子总体PowerLaw Index的P = 2.9 +/- 0.1。我们建议早期无线电耀斑可能是由于星际闪烁（ISS）造成的，这使无线电余波发射提高了ATCA灵敏度限制对分钟时标的敏感性限制。使用弱的ISS关系，我们能够对$ \ leq6 \ times 10^{16} $ cm的爆炸波大小放置在天空平面上的上限，这与$ 8 \ times10^{16} $ cm的理论前向冲击大小预测GRB 210702A的$ 8 \ times10^{16} $ cm。这代表了迄今为止的GRB爆炸波上最早的ISS大小约束，这表明了使用多个小时的积分对GRB进行快速（<1天）无线电随访的重要性，以捕获早期的余辉演化，并在宽频率范围内跟踪闪烁。
We observed the rapid radio brightening of GRB 210702A with the Australian Telescope Compact Array (ATCA) just 11hr post-burst, tracking early-time radio variability over a 5hr period on ~15min timescales at 9.0, 16.7, and 21.2GHz. A broken power-law fit to the 9.0GHz light curve showed that the 5hr flare peaked at a flux density of 0.4+/-0.1mJy at ~13hr post-burst with a steep rise and decline. The observed temporal and spectral evolution are not expected in the standard internal-external shock model, where forward and reverse shock radio emission evolves on much longer timescales. The early-time (<1day) optical and X-ray light curves from the Neil Gehrels Swift Observatory demonstrated typical afterglow forward shock behaviour, allowing us to use blast wave physics to determine a likely homogeneous circumburst medium and an emitting electron population power-law index of p=2.9+/-0.1. We suggest the early-time radio flare is likely due to weak interstellar scintillation (ISS), which boosted the radio afterglow emission above the ATCA sensitivity limit on minute timescales. Using weak ISS relations, we were able to place an upper limit on the size of the blast wave of $\leq6 \times 10^{16}$cm in the plane of the sky, which is consistent with the theoretical forward shock size prediction of $8\times10^{16}$cm for GRB 210702A at ~13h post-burst. This represents the earliest ISS size constraint on a GRB blast wave to date, demonstrating the importance of rapid (<1day) radio follow-up of GRBs using several-hour integrations to capture the early afterglow evolution, and to track scintillation over a broad frequency range.
