Jiang, Jin-Chen and Wang, Wei-Yang and Xu, Heng and Xu, Jiang-Wei and Zhang, Chun-Feng and Wang, Bo-Jun and Zhou, De-Jiang and Zhang, Yong-Kun and Niu, Jia-Rui and Lee, Ke-Jia and Zhang, Bing and Han, Jin-Lin and Li, Di and Zhu, Wei-Wei and Dai, Zi-Gao and Feng, Yi and Jing, Wei-Cong and Li, Dong-Zi and Luo, Rui and Miao, Chen-Chen and Niu, Chen-Hui and Tsai, Chao-Wei and Wang, Fa-Yin and Wang, Pei and Xu, Ren-Xin and Yang, Yuan-Pei and Yang, Zong-Lin and Yao, Ju-Mei and Yuan, Mao (2022) FAST Observations of an Extremely Active Episode of FRB 20201124A. III. Polarimetry. Research in Astronomy and Astrophysics, 22 (12). Art. No. 124003. ISSN 1674-4527. doi:10.1088/1674-4527/ac98f6. https://resolver.caltech.edu/CaltechAUTHORS:20230117-372591200.36
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Abstract
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 (∼500 rad m⁻² day⁻¹) previously reported during the rapid RM-variation phase, but is still higher than the one (≤1 rad m⁻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.
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Additional Information: | We thank the anonymous referee for providing valuable suggestions. This work made use of the data from FAST (Five-hundred-meter Aperture Spherical radio Telescope). FAST is a Chinese national mega-science facility, operated by National Astronomical Observatories, Chinese Academy of Sciences. This work is supported by the National SKA Program of China (2020SKA0120100, 2020SKA0120200), the National Key R&D Program of China (2017YFA0402602), the National Natural Science Foundation of China (NSFC, Grant No. 12041303), the CAS-MPG LEGACY project and funding from the Max-Planck Partner Group. J. L. Han is supported by the National Natural Science Foundation of China (NSFC, Grant Nos. 11988101 and 11833009) and the Key Research Program of the Chinese Academy of Sciences (Grant No. QYZDJ-SSW-SLH021); D. J. Zhou is supported by the Cultivation Project for the FAST scientific Payoff and Research Achievement of CAMS-CAS. Y. Feng is supported by the Key Research Project of Zhejiang Lab no. 2021PE0AC0. Y.P.Y. is supported by National Natural Science Foundation of China (Grant No. 12003028) and the China Manned Spaced Project (CMS-CSST-2021-B11). | ||||||||||||||||||||||||||||||||
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Issue or Number: | 12 | ||||||||||||||||||||||||||||||||
DOI: | 10.1088/1674-4527/ac98f6 | ||||||||||||||||||||||||||||||||
Record Number: | CaltechAUTHORS:20230117-372591200.36 | ||||||||||||||||||||||||||||||||
Persistent URL: | https://resolver.caltech.edu/CaltechAUTHORS:20230117-372591200.36 | ||||||||||||||||||||||||||||||||
Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | ||||||||||||||||||||||||||||||||
ID Code: | 118833 | ||||||||||||||||||||||||||||||||
Collection: | CaltechAUTHORS | ||||||||||||||||||||||||||||||||
Deposited By: | Research Services Depository | ||||||||||||||||||||||||||||||||
Deposited On: | 10 Feb 2023 20:59 | ||||||||||||||||||||||||||||||||
Last Modified: | 10 Feb 2023 20:59 |
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