As the third paper in the multiple-part series,we report the statistical properties of radio bursts detected from the repeating fast radio burst(FRB)source FRB 20201124A with the Five-hundred-meter Aperture Spherical radio Telescope during an extremely active episode between the 25th and 28th of September 2021(UT).We focus on the polarization properties of 536 bright bursts with S/N＞50.We found that the Faraday rotation measures(RMs)monotonically dropped from-579 to-605 rad m-2 in the 4 day window.The RM values were compatible with the values(-300 to-900 rad m-2)reported 4 months ago.However,the RM evolution rate in the current observation window was at least an order of magnitude smaller than the one(～500radm-2day-1)previously reported during the rapid RM-variation phase,but is still higher than the one(≤1 rad in-2 day-1)during the later RM no-evolution phase.The bursts of FRB 20201124A were highly polarized with the total degree of polarization(circular plus linear)greater than 90％for more than 90％of all bursts.The distribution of linear polarization position angles(PAs),degree of linear polarization(L/I)and degree of circular polarization(V/I)can be characterized with unimodal distribution functions.During the observation window,the distributions became wider with time,i.e.,with larger scatter,but the centroids of the distribution functions remained nearly constant.For individual bursts,significant PA variations(confidence level 5σ)were observed in 33％of all bursts.The polarization of single pulses seems to follow certain complex trajectories on the Poincaré sphere,which may shed light on the radiation mechanism at the source or the plasma properties along the path of FRB propagation.

Jin-Chen Jiang;Wei-Yang Wang;Heng Xu;Jiang-Wei Xu;Chun-Feng Zhang;Bo-Jun Wang;De-Jiang Zhou;Yong-Kun Zhang;Jia-Rui Niu;Ke-Jia Lee;Bing Zhang;Jin-Lin Han;Di Li;Wei-Wei Zhu;Zi-Gao Dai;Yi Feng;Wei-Cong Jing;Dong-Zi Li;Rui Luo;Chen-Chen Miao;Chen-Hui Niu;Chao-Wei Tsai;Fa-Yin Wang;Pei Wang;Ren-Xin Xu;Yuan-Pei Yang;Zong-Lin Yang;Ju-Mei Yao;Mao Yuan

Department of Astronomy,Peking University,Beijing 100871,China;National Astronomical Observatories,Chinese Academy of Sciences,Beijing 100101,China;Kavli Institute for Astronomy and Astrophysics,Peking University,Beijing 100871,China;School of Astronomy,University of Chinese Academy of Sciences,Beijing 100049,China;Department of Physics and Astronomy,University of Nevada,Las Vegas,NV 89154,USA;CAS Key Laboratory of FAST,NAOC,Chinese Academy of Sciences,Beijing 100101,China;Research Center for Intelligent Computing Platforms,Zhejiang Laboratory,Hangzhou 311100,China;NAOC-UKZN Computational Astrophysics Centre,University of KwaZulu-Natal,Durban 4000,South Africa;Department of Astronomy,University of Science and Technology of China,Hefei 230026,China;Cahill Center for Astronomy and Astrophysics,MC 249-17,California Institute of Technology,Pasadena,CA 91125,USA;CSIRO Space and Astronomy,P.O.Box 76,Epping,NSW 1710,Australia;School of Astronomy and Space Science,Nanjing University,Nanjing 210093,China;Key Laboratory of Modern Astronomy and Astrophysics(Nanjing University),Ministry of Education,China;South-Western Institute For Astronomy Research,Yunnan University,Yunnan 650504,China;Xinjiang Astronomical Observatory,Chinese Academy of Sciences,Urumqi 830011,China

天文和天体物理学研究

[1]Jin-Chen Jiang;Wei-Yang Wang;Heng Xu;Jiang-Wei Xu;Chun-Feng Zhang;Bo-Jun Wang;De-Jiang Zhou;Yong-Kun Zhang;Jia-Rui Niu;Ke-Jia Lee;Bing Zhang;Jin-Lin Han;Di Li;Wei-Wei Zhu;Zi-Gao Dai;Yi Feng;Wei-Cong Jing;Dong-Zi Li;Rui Luo;Chen-Chen Miao;Chen-Hui Niu;Chao-Wei Tsai;Fa-Yin Wang;Pei Wang;Ren-Xin Xu;Yuan-Pei Yang;Zong-Lin Yang;Ju-Mei Yao;Mao Yuan-.FAST Observations of an Extremely Active Episode of FRB 20201124A.Ⅲ.Polarimetry)[J].天文和天体物理学研究,2022(12):81-98

20201124A,Polarimetry,500radm,2day

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