[论文解读] A fast radio burst with sub-millisecond quasi-periodic structure

Inés Pastor-Marazuela, J. van Leeuwen+32 more|arXiv (Cornell University)|Feb 16, 2022

Pulsars and Gravitational Waves Research参考文献 88被引用 6

一句话总结

本文介绍了FRB 20201020A，这是一个在Westerbork综合孔径射电望远镜通过Apertif系统探测到的快速射电暴，其具有亚毫秒量级的准周期性结构。该爆发表现出五个分量，平均间距约为0.415毫秒，周期性显著性约为2.5σ，表明其可能属于一类新型FRB形态，极有可能与磁星磁层过程相关。

ABSTRACT

Fast radio bursts (FRBs) are extragalactic radio transients of extraordinary luminosity. Studying the diverse temporal and spectral behaviour recently observed in a number of FRBs may help determine the nature of the entire class. For example, a fast spinning or highly magnetised neutron star might generate the rotation-powered acceleration required to explain the bright emission. Periodic, sub-second components, suggesting such rotation, were recently reported in one FRB, and potentially in two more. Here we report the discovery of FRB 20201020A with Apertif, an FRB showing five components regularly spaced by 0.415 ms. This sub-millisecond structure in FRB 20201020A carries important clues about the progenitor of this FRB specifically, and potentially about that of FRBs in general. We thus contrast its features to the predictions of the main FRB source models. We perform a timing analysis of the FRB 20201020A components to determine the significance of the periodicity. We compare these against the timing properties of the previously reported CHIME FRBs with sub-second quasi-periodic components, and against two Apertif bursts from repeating FRB 20180916B that show complex time-frequency structure. We find the periodicity of FRB 20201020A to be marginally significant at 2.5$σ$. Its repeating subcomponents cannot be explained as a pulsar rotation since the required spin rate of over 2 kHz exceeds the limits set by typical neutron star equations of state and observations. The fast periodicity is also in conflict with a compact object merger scenario. These quasi-periodic components could, however, be caused by equidistant emitting regions in the magnetosphere of a magnetar. The sub-millisecond spacing of the components in FRB 20201020A, the smallest observed so far in a one-off FRB, may rule out both neutron-star rotation and binary mergers as the direct source of quasi-periodic FRBs.

研究动机与目标

• 研究快速射电暴（FRBs）中是否存在亚毫秒 timescale 的准周期性子结构。
• 确定FRB 20201020A在其子成分中是否表现出统计上显著的周期性。
• 将FRB 20201020A的形态与其他已知具有准周期性特征的FRB（如CHIME/FRB探测结果）进行比较。
• 探讨此类周期性结构的物理起源，排除脉泽星和双星并合模型的可能性。
• 评估所观测到的结构是否与磁星微结构或脉泽星样辐射过程一致。

提出的方法

• 利用Westerbork综合孔径射电望远镜的Apertif系统数据，对FRB 20201020A进行定时分析。
• 应用$ ilde{S}$-检验评估子成分中周期性的显著性，得出显著性约为2.5σ。
• 将FRB 20201020A的子成分间距与CHIME/FRB的FRB 20210206A和FRB 20210213A的特征进行比较。
• 分析FRB 20180916B的爆发A17和A53，重点关注子成分间距与周期性显著性。
• 评估竞争性物理模型，包括亚毫秒脉泽星和双紧凑天体并合模型，并予以排除。
• 通过类比脉泽星子脉冲与磁星单脉冲微结构，推断该准周期性可能源于磁层起源。

实验结果

研究问题

• RQ1 FRB 20201020A是否在亚毫秒 timescale 上表现出统计上显著的准周期性子结构？
• RQ2 FRB 20201020A中的周期性与CHIME/FRB 20210206A和20210213A等其他已知准周期性FRB相比如何？
• RQ3 所观测到的亚毫秒周期性是否可由已知天体物理模型（如亚毫秒脉泽星或双星并合）解释？
• RQ4 FRB 20201020A的形态是否与磁星中观测到的发射过程（如单脉冲微结构）一致？
• RQ5 何种物理机制可产生FRB中此类规则且短 timescale 的结构？其与典型重复FRB辐射有何不同？

主要发现

• FRB 20201020A表现出五个明显的子成分，平均间距约为0.415毫秒，处于亚毫秒时间尺度。
• FRB 20201020A的周期性显著性约为2.5σ，虽低于标准的3σ阈值，但与CHIME/FRB 20210206A和20210213A的显著性水平相当。
• FRB 20180916B的爆发A17表现出约1毫秒的子成分间距，且通过$ ilde{S}$-检验的周期性显著性超过3σ。
• 同一FRB的爆发A53平均子成分间距约为1.7毫秒，包含至少11个分量，但未表现出确凿的周期性。
• 由于时标与能量约束，亚毫秒脉泽星和双紧凑天体并合模型被排除为FRB 20201020A的起源机制。
• FRB 20201020A的形态最符合磁星磁层过程，与产生射电明亮磁星单脉冲微结构的机制相似。