FAST detect sustained activities and a bright burst from FRB20201124A

ATel #15288; Pei Wang(NAOC), Weiwei Zhu(NAOC), Yongkun Zhang(NAOC), Dejiang Zhou(NAOC), Heng Xu(PKU), Di Li(NAOC), Jinlin Han(NAOC), Kejia Lee(PKU), Wenfei Yu(SHAO), Bing Zhang(UNLV), Jianping Yuan(XAO), Jian Li(XAO), Yanling Liu(XAO), Yi Feng(ZL), Jiarui Niu(NAOC), Jiangwei Xu(PKU), Jinchen Jiang(PKU), Chenhui Niu(NAOC), Chunfeng Zhang(PKU), Bojun Wang(PKU), Weiyang Wang(PKU), Jumei Yao(XAO)
on 20 Mar 2022; 09:39 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Pei Wang (wangpei@nao.cas.cn)

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We have been carrying out daily to weekly monitoring of FRB 20201124A (RA = 05h08m03.459s, DEC = +26d03m39.14s)^[1] with the central beam of the FAST L-band 19 beam receiver in the frequency range of 1.0-1.5 GHz, and the data stream was recorded with a sampling time of 49.152 μs for 4096 frequency channels. In addition to the bursts from an active episode between April and June, 2021^[2], more than three thousand bursts have been detected in 25 observing hours since February 2022. A bright burst was detected with a peak S/N∼150 for 2.8 ms duration at an arrival time of UT 10:12:38.85488, March 17 2022, i.e. 59655.4254277447 MJD (correcting to solar system barycenter with an infinite frequency). The flux and polarization of the burst was calibrated with noise CAL injection. The burst is nearly 100% linearly polarized with a RM = -673 rad/m², a best estimate of dispersion measure DM = 410.9±0.5 pc cm^-3. A few digital samples are saturated in the 8-bit system, resulting in the lower limit of peak flux density of 367±2 mJy (corresponding to an isotropic peak luminosity (1.03±0.06)x10⁴¹ erg/s).

FRB 20201124A stays active. We encourage more target-of-opportunity observations 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.

Reference:
[1] Nimmo, K. et al., 2021, arXiv:2111.01600
[2] H. Xu, J. R. Niu and P. Chen et al., 2022, arXiv:2111.11764v1

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The dynamic spectrum diagram of the detected burst - Averaged polarization profile and the dynamic spectrum diagram of a burst from FRB20201124A, detected with FAST L-band (1.05-1.45 GHz) 19-beam receiver. The data in each frequency channel are incoherently de-dispersed with DM=410.9 pc cm^-3. The arrival time of burst peak at the solar system barycenter (TDB) is MJD = 59655.4254277447 (correcting to an infinite frequency). The black, red, and blue lines represent Stokes I, the linear polarization and Stokes V, respectively.

The dynamic spectrum diagram of the detected burst