Ninety percent circular polarization detected in a repeating fast radio burst

Fast radio bursts (FRBs) are extra-galactic sources with unknown physical mechanisms. They emit millisecond-duration radio pulses with isotropic equivalent energy of [Formula: see text]-[Formula: see text] ergs. This corresponds to a brightness temperature of FRB emission typically reaching the level of [Formula: see text] K, but can be as high as above [Formula: see text] K for sub-microsecond timescale structures, suggesting the presence of underlying coherent relativistic radiation mechanisms. Polarization carries key information to understand the physical origin of FRBs, with linear polarization usually tracing the geometric configuration of magnetic fields and circular polarization probing both intrinsic radiation mechanisms and propagation effects. Here we show that the repeating source FRB 20201124A emits [Formula: see text] circularly polarized radio pulses. Such a high degree of circular polarization was unexpected in theory and unprecedented in observation in the case of FRBs, since such a high degree of circular polarization was only common among solar or Jovian radio activities, attributed to the sub-relativistic electrons. We note that there is no obvious correlation between the degree of circular polarization and burst fluence. Besides the high degree of circular polarization, we also detected a rapid swing and orthogonal jump in the position angle of linear polarization. The detection of high-degree circular polarization in FRB 20201124A, together with its linear polarization properties that show orthogonal modes, place strong constraints on FRB physical mechanisms, calling for an interplay between magnetospheric radiation and propagation effects in shaping the observed FRB radiation.

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Publication Details

Journal
National Science Review
Published
2024-09-09
DOI
https://doi.org/10.1093/nsr/nwae293
Citations
16
Primary Topic
Pulsars and Gravitational Waves Research
Type
article
Field-Weighted Citation Impact
5.30

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article

Ninety percent circular polarization detected in a repeating fast radio burst

J. L. Han, Youling Yue, Jiarui Niu, Kejia Lee et al.
16 citations
National Science Review
Pulsars and Gravitational Waves Research
5.30
article

Ninety percent circular polarization detected in a repeating fast radio burst

J. L. Han, Youling Yue, Jiarui Niu, Kejia Lee, Zhixuan Li, Renxin Xu, Peng Jiang, Yuxiang Huang, D. J. Zhou, Heng Xu, Yan Zhu, Jinghai Sun, Weiyang Wang, Yunpeng Men, Yuanhong Qu, Yonghua Xu, Rui Luo, Jinchen Jiang, Yongkun Zhang, Weiwei Zhu, Dongzi Li, Bojun Wang, Ye Li, Lin Wang, Hui Li, Lei Qian, Jiangwei Xu, Chunfeng Zhang, Shunshun Cao, Shuo Cao, J. P. Yuan, Rui Yao, Longfei Hao, Bing Zhang, Yuan-Pei Yang, Hengqian Gan, Dongjun Yu
article en
16 citations

Abstract

Fast radio bursts (FRBs) are extra-galactic sources with unknown physical mechanisms. They emit millisecond-duration radio pulses with isotropic equivalent energy of [Formula: see text]-[Formula: see text] ergs. This corresponds to a brightness temperature of FRB emission typically reaching the level of [Formula: see text] K, but can be as high as above [Formula: see text] K for sub-microsecond timescale structures, suggesting the presence of underlying coherent relativistic radiation mechanisms. Polarization carries key information to understand the physical origin of FRBs, with linear polarization usually tracing the geometric configuration of magnetic fields and circular polarization probing both intrinsic radiation mechanisms and propagation effects. Here we show that the repeating source FRB 20201124A emits [Formula: see text] circularly polarized radio pulses. Such a high degree of circular polarization was unexpected in theory and unprecedented in observation in the case of FRBs, since such a high degree of circular polarization was only common among solar or Jovian radio activities, attributed to the sub-relativistic electrons. We note that there is no obvious correlation between the degree of circular polarization and burst fluence. Besides the high degree of circular polarization, we also detected a rapid swing and orthogonal jump in the position angle of linear polarization. The detection of high-degree circular polarization in FRB 20201124A, together with its linear polarization properties that show orthogonal modes, place strong constraints on FRB physical mechanisms, calling for an interplay between magnetospheric radiation and propagation effects in shaping the observed FRB radiation.

National Science ReviewVol. 12(2)
University of Nevada, Las Vegas (US), Yunnan University (CN), Chinese Academy of Sciences (CN), Princeton University (US), Peking University (CN), Xinjiang Astronomical Observatory (CN), Yunnan Observatories (CN), Purple Mountain Observatory (CN), Guangzhou University (CN), Kavli Institute for Theoretical Sciences (CN), Astronomy and Space (AU), Max Planck Institute for Radio Astronomy (DE), National Astronomical Observatories (CN), University of Chinese Academy of Sciences (CN)
National Natural Science Foundation of China, Chinese Academy of Sciences, National Astronomical Observatories, Chinese Academy of Sciences
Openalex Percentile: Top 4%
Pulsars and Gravitational Waves Research
5.30
DOIOpen Access PDFOpenAlex
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