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<p>Fast radio bursts (FRBs) are bright, millisecond-duration radio emissions originating from cosmological distances. In this study, we report multi-year polarization measurements of four repeating FRBs initially discovered by the Canadian Hydrogen Intensity Mapping Experiment (CHIME): FRBs 20190117A, 20190208A, 20190303A, and 20190417A. We observed the four repeating FRBs with the Five-hundred-meter Aperture Spherical Radio Telescope (FAST), detecting a total of 66 bursts. Two bursts from FRB 20190417A exhibit a circular polarization signal-to-noise ratio greater than 7, with the highest circular polarization fraction recorded at 35.7%. While the bursts from FRBs 20190208A and 20190303A are highly linearly polarized, those from FRBs 20190117A and 20190417A show depolarization due to multi-path propagation, with <i>σ</i><sub>RM</sub> = 2.78 ± 0.05 and 5.19 ± 0.09 rad m<sup>−2</sup>, respectively. The linear polarization distributions among five repeating FRBs—FRBs 20190208A, 20190303A, 20201124A, 20220912A, and 20240114A—are nearly identical but show distinct differences from those of non-repeating FRBs. FRBs 20190117A, 20190303A, and 20190417A exhibit substantial rotation measure (RM) variations between bursts, joining other repeating FRBs in this behavior. Combining these findings with published results, 64% of repeating FRBs show RM variations greater than 50 rad m<sup>−2</sup>, and 21% exhibit RM reversals. A significant proportion of repeating FRBs reside in a dynamic magneto-ionic environment. The structure function of RM variations shows a power-law index of <i>γ</i> ∼ (0–0.8), corresponding to a shallow power spectrum <i>α</i> = −(<i>γ +</i> 2) ∼ −(2.0–2.8) of turbulence, if the RM variations are attributed to turbulence. This suggests that the variations are dominated by small-scale RM density fluctuations. We perform K-S tests to compare the RMs of repeating and non-repeating FRBs, which reveal a marginal dichotomy in the distribution of their RMs. We caution that the observed dichotomy may be due to the small sample size and selection biases.</p>

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Multi-year polarimetric monitoring of four CHIME-discovered repeating fast radio bursts with FAST

  • 期刊论文

  • 发表日期：

    2025年6月26日

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  • Yi Feng,
  • Yong-Kun Zhang,
  • Jintao Xie,
  • Yuan-Pei Yang,
  • Yuanhong Qu,
  • Dengke Zhou,
  • Di Li,
  • Bing Zhang,
  • Weiwei Zhu,
  • Wenbin Lu,
  • Jiaying Xu,
  • Chenchen Miao,
  • Shiyan Tian,
  • Pei Wang,
  • Ju-Mei Yao,
  • Chen-Hui Niu,
  • Jiarui Niu,
  • Heng Xu,
  • Jinchen Jiang,
  • Dejiang Zhou,
  • Zenan Liu,
  • Chao-Wei Tsai,
  • Zigao Dai,
  • Xuefeng Wu,
  • Fayin Wang,
  • Jinlin Han,
  • Kejia Lee,
  • Renxin Xu,
  • Yongfeng Huang,
  • Yuanchuan Zou,
  • Jinhuang Cao,
  • Xianglei Chen,
  • Jianhua Fang,
  • Dongzi Li,
  • Ye Li,
  • Wanjin Lu,
  • Jiawei Luo,
  • Jintao Luo,
  • Rui Luo,
  • Fen Lyu,
  • Bojun Wang,
  • Weiyang Wang,
  • Qin Wu,
  • Mengyao Xue,
  • Di Xiao,
  • Wenfei Yu,
  • Jianping Yuan,
  • Chunfeng Zhang,
  • Junshuo Zhang,
  • Lei Zhang,
  • Songbo Zhang,
  • Rushuang Zhao,
  • Yuhao Zhu

摘要

Fast radio bursts (FRBs) are bright, millisecond-duration radio emissions originating from cosmological distances. In this study, we report multi-year polarization measurements of four repeating FRBs initially discovered by the Canadian Hydrogen Intensity Mapping Experiment (CHIME): FRBs 20190117A, 20190208A, 20190303A, and 20190417A. We observed the four repeating FRBs with the Five-hundred-meter Aperture Spherical Radio Telescope (FAST), detecting a total of 66 bursts. Two bursts from FRB 20190417A exhibit a circular polarization signal-to-noise ratio greater than 7, with the highest circular polarization fraction recorded at 35.7%. While the bursts from FRBs 20190208A and 20190303A are highly linearly polarized, those from FRBs 20190117A and 20190417A show depolarization due to multi-path propagation, with σRM = 2.78 ± 0.05 and 5.19 ± 0.09 rad m−2, respectively. The linear polarization distributions among five repeating FRBs—FRBs 20190208A, 20190303A, 20201124A, 20220912A, and 20240114A—are nearly identical but show distinct differences from those of non-repeating FRBs. FRBs 20190117A, 20190303A, and 20190417A exhibit substantial rotation measure (RM) variations between bursts, joining other repeating FRBs in this behavior. Combining these findings with published results, 64% of repeating FRBs show RM variations greater than 50 rad m−2, and 21% exhibit RM reversals. A significant proportion of repeating FRBs reside in a dynamic magneto-ionic environment. The structure function of RM variations shows a power-law index of γ ∼ (0–0.8), corresponding to a shallow power spectrum α = −(γ + 2) ∼ −(2.0–2.8) of turbulence, if the RM variations are attributed to turbulence. This suggests that the variations are dominated by small-scale RM density fluctuations. We perform K-S tests to compare the RMs of repeating and non-repeating FRBs, which reveal a marginal dichotomy in the distribution of their RMs. We caution that the observed dichotomy may be due to the small sample size and selection biases.