A highly depolarized burst from FRB 20121102A with significantly smaller RM as revealed by FAST
ATel #15980; Yi Feng(Zhejiang Lab), Jinchen Jiang(NAOC), Dejiang Zhou(NAOC), Pei Wang(NAOC), Junshuo Zhang(NAOC), Di Li(NAOC), Weiwei Zhu(NAOC), Bing Zhang(UNLV), Yongkun Zhang(NAOC), Yuan-Pei Yang(YNU), Jinlin Han(NAOC), Kejia Lee(PKU&NAOC), Ye Li(PMO), Rui Luo(GZHU), Chenchen Miao(NAOC), Chenhui Niu(NAOC), Jiarui Niu(NAOC), ChaoWei Tsai(NAOC), Bojun Wang(NAOC), Fayin Wang(NJU), Weiyang Wang(UCAS), Xuefeng Wu(PMO), Heng Xu(NAOC), Jumei Yao(XAO), Wenfei Yu(SHAO), Chunfeng Zhang(NAOC), Songbo Zhang(PMO)
on 7 Apr 2023; 12:10 UT
Credential Certification: Pei Wang (wangpei@nao.cas.cn)
Subjects: Radio, Transient, Fast Radio Burst
Referred to by ATel #: 15981
FAST has been monitoring FRB 20121102A nearly biweekly since the beginning of 2023. The central beam of the FAST L-band-focal-plane Array of 19 beams (FLAN) was pointing to RA = 05h31m58.70s, DEC = +33d08m52.5s (Chatterjee et al. 2017). Pulsar-searching data were taken with a 49.152 microsecond sampling and 4096 frequency channels covering 1.0 GHz to 1.5 GHz.
Since the last active episode (ATEL 13959), FAST detected at least 100 bursts from FRB 20121102A in 2023. During the observation on March 3rd, a bright burst was detected at MJD 60006.51262001.
The Faraday rotation measure (RM) derived from this polarised pulse by using the RM-synthesis method is +30755-15+10 rad m-2, continuing the decreasing trend of FRB 20121102A's RM, which had been observed between 2016-2019 (Michill et al. 2018; Hilmarsson et al. 2021). Our measurement is the first RM measurement since 2019 and is much smaller than the earlier detections (Michill et al. 2018; Hilmarsson et al. 2021), suggesting significant changes of the environment, which was also indicated by the DM decrease (ATEL 13959). The average decrease of RM is roughly 1.02 x 105rad m-2 per year since 2019. We encourage more follow-up monitoring efforts with multi-band facilities.
FAST is a Chinese national mega-science facility, built and operated by the National Astronomical Observatories, Chinese Academy of Sciences (NAOC). We appreciate all the members in the FAST FRB key science project collaboration for their support and assistance during the observations.
Chatterjee, S.; Law, C. J.; Wharton, R. S. et al. 2017, Nature, 541, 58
Hilmarsson, G. H., Michilli, D., Spitler, L. G., et al. 2021, ApJL, 908, L10
Michilli, D., Seymour, A., Hessels, J. W. T., et al. 2018,Nature, 553, 182
Wang, P., Men, Y., Zhou, D., et al. 2020, The Astronomerâs Telegram, 13959, 1
