Parkes observations for project P1068 semester 2021APRS_18

In the fast-moving world of Fast Radio Bursts (FRBs), the critical question of what fraction of FRBs emit repeat bursts remains unanswered. Of order 20 repeating FRBs are now known, and their spectro-temporal properties hint at differences with apparently non-repeating bursts - the poor statistics preclude a definitive diagnosis. FRB 180301 is a promising source for further study for multiple reasons: it is an active repeater similar to the FRB 121102 and the most active FRB source visible to Parkes, and it shows diverse polarization properties across the repeat bursts. We have detected multiple repeat bursts from this source in our campaign last semester. The signal-to-noise ratio (S/N) of these detections are not sufficiently significant to measure their spectro-polarimetric properties. We request Parkes observations with the UWL receiver to continue the monitoring of this FRB source in order to characterize the broadband emission properties. Some of the key goals for these future observations are: to constrain the repetition rate, identify any variation of pulse characteristics over time, measure the polarimetric properties and provide insight into the emission mechanisms. The diverse polarization angle swings in the FAST detections and significant circular polarization in the original Parkes detection indicate the progenitor is embedded in an extreme magneto-ionic environment with complex field structure that has not been seen before. Understanding these diverse polarization properties from this source could be the key to distinguish repeater sources from the apparent non-repeaters ones.

在快速射电暴（Fast Radio Bursts，以下简称FRBs）飞速发展的研究领域中，仍有一个核心问题尚未得到解答：究竟有多大比例的快速射电暴会重复爆发。目前已发现约20个重复爆发的FRBs，它们的谱时特性暗示其与单次爆发的快速射电暴存在差异，但受限于统计样本不足，无法得出确定性结论。FRB 180301是极具后续研究价值的暴源，原因有三：其一，它是与FRB 121102类似的活跃重复暴源；其二，它是帕克斯望远镜（Parkes）可观测到的最活跃的FRB源；其三，其重复爆发过程中展现出丰富多样的偏振特性。在上一学期的观测项目中，我们已从该暴源中探测到多次重复爆发信号，但此次探测的信噪比（signal-to-noise ratio, S/N）尚未达到足够精度，无法对其谱偏振特性开展定量测量。为此我们申请使用帕克斯望远镜搭载的UWL接收机开展观测，以持续监测该FRB源，从而完整刻画其宽频辐射特性。此次未来观测的核心目标包括：约束重复爆发率、探究脉冲特性随时间的演化规律、定量测量偏振特性，以及为揭示辐射机制提供关键理论线索。500米口径球面射电望远镜（Five-hundred-meter Aperture Spherical radio Telescope, FAST）探测到的多样偏振角摆动，以及帕克斯望远镜初始观测中发现的显著圆偏振特征，均表明该暴源的前身天体处于此前从未被观测到的极端磁离子环境中，且其磁场结构极为复杂。对该暴源丰富多样的偏振特性开展研究，或将成为区分重复暴源与单次暴源的关键突破口。