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arXiv 2109.11535astro-ph.HE
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重复快速射电暴源FRB 20201124 A的圆极化射电辐射

Circularly polarized radio emission from the repeating fast radio burst source FRB 20201124A

Pravir Kumar, Ryan M. Shannon, Marcus E. Lower, Shivani Bhandari, Adam T. Deller, Chris Flynn, Evan F. Keane

摘要:

产生快速射电暴(FRB)辐射的机制还知之甚少。有针对性地监测重复FRB源提供了机会,以一次性突发不可能的方式充分表征发射特性。在这里,我们报告了FRB 20201124 A源的观测结果,澳大利亚平方公里阵列探路者(ASKAP)和帕克斯64米射电望远镜(Murriyang)的超宽带低(UWL)接收器。该源在2021年4月初进入了一个发射明亮爆发的时期。我们已经探测到了16个来自这个源的爆发。ASKAP探测到的爆发之一是从重复FRB源观测到的最亮爆发,推断通量为$640\pm70$ μ ms。在Parkes UWL探测到的五个爆发中,没有一个显示出1.1- 4 GHz范围内的任何发射。所有的UWL爆发都是高度极化的,它们的法拉第旋转测量(RM)显示出明显的变化。我们得到了一个平均RM的$-614$ rad m $^{-2}$的FRB源的$16$ rad m $^{-2}$在UWL爆发的标准偏差。在其中一个UWL爆发中,我们看到了显著的圆偏振发射的证据,其分数范围为$47\pm1$ %。如此高的圆偏振度在重复FRB源的爆发中从未见过。我们还看到了在这个UWL重复突发脉冲轮廓中的线性偏振位置角的显著变化的证据。重复脉冲群发射的模型需要考虑脉冲群极化特性的多样性。

英文摘要:

The mechanism that produces fast radio burst (FRB) emission is poorly understood. Targeted monitoring of repeating FRB sources provides the opportunity to fully characterize the emission properties in a manner impossible with one-off bursts. Here, we report observations of the source of FRB 20201124A, with the Australian Square Kilometre Array Pathfinder (ASKAP) and the ultra-wideband low (UWL) receiver at the Parkes 64-m radio telescope (Murriyang). The source entered a period of emitting bright bursts during early 2021 April. We have detected 16 bursts from this source. One of the bursts detected with ASKAP is the brightest burst ever observed from a repeating FRB source with an inferred fluence of $640\pm70$ Jy ms. Of the five bursts detected with the Parkes UWL, none display any emission in the range 1.1--4 GHz. All UWL bursts are highly polarized, with their Faraday rotation measures (RMs) showing apparent variations. We obtain an average RM of $-614$ rad m$^{-2}$ for this FRB source with a standard deviation of $16$ rad m$^{-2}$ in the UWL bursts. In one of the UWL bursts, we see evidence of significant circularly polarized emission with a fractional extent of $47\pm1$ per cent. Such a high degree of circular polarization has never been seen before in bursts from repeating FRB sources. We also see evidence for significant variation in the linear polarization position angle in the pulse profile of this UWL repeat burst. Models for repeat burst emission will need to account for the increasing diversity in the burst polarization properties.

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