Towards solving the origin of circular polarisation in FRB 20180301A

IF 4.7 3区 物理与天体物理 Q1 ASTRONOMY & ASTROPHYSICS
Pavan Uttarkar, Ryan M Shannon, Marcus E Lower, Pravir Kumar, Danny C Price, A T Deller, K Gourdji
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Abstract

Fast Radio Bursts (FRBs) are short-timescale transients of extragalactic origin. The number of detected FRBs has grown dramatically since their serendipitous discovery from archival data. Some FRBs have also been seen to repeat. The polarimetric properties of repeating FRBs show diverse behaviour and, at times, extreme polarimetric morphology, suggesting a complex magneto-ionic circumburst environment for this class of FRB. The polarimetric properties such as circular polarisation behaviour of FRBs are crucial for understanding their surrounding magnetic-ionic environment. The circular polarisation previously observed in some of the repeating FRB sources has been attributed to propagation effects such as generalised Faraday rotation (GFR), where conversion from linear to circular polarisation occurs due to the non-circular modes of transmission in relativistic plasma. The discovery burst from the repeating FRB 20180301A showed significant frequency-dependent circular polarisation behaviour, which was initially speculated to be instrumental due to a sidelobe detection. Here we revisit the properties given the subsequent interferometric localisation of the burst, which indicates that the burst was detected in the primary beam of the Parkes/Murriyang 20-cm multibeam receiver. We develop a Bayesian Stokes-Q, U, and V fit method to model the GFR effect, which is independent of the total polarised flux parameter. Using the GFR model we show that the rotation measure (RM) estimated is two orders of magnitude smaller and opposite sign (∼28 rad m−2) than the previously reported value. We interpret the implication of the circular polarisation on its local magnetic environment and reinterpret its long-term temporal evolution in RM.
努力解决 FRB 20180301A 中圆形极化的起源问题
快速射电暴(FRBs)是源自河外星系的短时瞬变。自从从档案数据中偶然发现快速射电暴以来,探测到的快速射电暴数量急剧增加。有些 FRB 还出现了重复现象。重复出现的 FRB 的偏振特性表现出多种多样的行为,有时还会出现极端的偏振形态,这表明这类 FRB 处于复杂的磁电离环爆环境中。FRB的圆极化行为等极化特性对于了解其周围的磁电离环境至关重要。以前在一些重复 FRB 源中观测到的圆极化现象被归因于传播效应,如广义法拉第旋转(GFR),由于相对论等离子体中的非圆传输模式,线性极化会转换为圆极化。来自重复FRB 20180301A的发现脉冲串显示了显著的频率依赖性圆极化行为,最初推测这是由于侧射探测造成的。在此,我们重新审视了这一特性,因为随后的干涉定位表明,该爆发是在 Parkes/Murriyang 20 厘米多波束接收器的主波束中探测到的。我们开发了一种贝叶斯斯托克斯-Q、U 和 V 拟合方法来模拟 GFR 效应,它与总偏振通量参数无关。利用 GFR 模型,我们发现估计的旋转量(RM)比之前报告的值小两个数量级,且符号相反(∼28 rad m-2)。我们解释了圆极化对其局部磁环境的影响,并重新解释了其在RM中的长期时间演变。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
CiteScore
9.10
自引率
37.50%
发文量
3198
审稿时长
3 months
期刊介绍: Monthly Notices of the Royal Astronomical Society is one of the world''s leading primary research journals in astronomy and astrophysics, as well as one of the longest established. It publishes the results of original research in positional and dynamical astronomy, astrophysics, radio astronomy, cosmology, space research and the design of astronomical instruments.
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