FRB121102 is active again as revealed by FAST

ATel #13959; Pei Wang(NAOC), Yunpeng Men(PKU), Dejiang Zhou(NAOC), Yongkun Zhang(NAOC), Tao An(SHAO), Yi Feng(NAOC), Jinlin Han(NAOC), Jinchen Jiang(PKU), Kejia Lee(PKU), Di Li(NAOC), Chenhui Niu(NAOC), Chenchen Miao(NAOC), Ningyu Tang(NAOC), Bojun Wang(PKU), Fayin Wang(NJU), Xuefeng Wu(PMO), Heng Xu(PKU), Jiangwei Xu(PKU), Jumei Yao(NAOC), Wenfei Yu(SHAO), Bing Zhang(UNLV), Chunfeng Zhang(PKU), Weiwei Zhu(NAOC)
on 21 Aug 2020; 16:49 UT
Credential Certification: Di Li (dili@nao.cas.cn)

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FAST is monitoring FRB 121102 for two to three hours at following dates since March of this year until now: (UTC) 12-14th Mar., 7th Apr., 16th May, 1st Jun., 7th Jun, 29th Jul. and 17th Aug. The central beam of the FAST L-band Array of 19-beams was pointed to RA = 05h31m58.70s, DEC = +33d08m52.5s (Chatterjee et al. 2017; Marcote et al. 2017), covering the frequency range from 1.05 GHz to 1.45 GHz. The pulsar-searching data were always taken with a 50 microsecond sampling and 4K frequency channels. Following non-detections until July 29th, 2020 (between UTC 2020-07-28 23:55:00 and UTC 2020-07-29 00:55:00), FAST detected at least 12 bursts from FRB121102 with the estimated fluence between 0.03 and 0.2 Jy ms on August 17th, 2020 (between UTC 2020-08-17 01:35 and UTC 2020-08-17 03:35), suggesting that this repeater is likely in another active phase. The peak flux density is estimated based on the SNR and the gain provided by the observatory. The brightest pulse is roughly 44 mJy. Rajwade et al. (2020) suggested that FRB121102's burst activity has an on-off period of ~156.9 days. Cruces et al. (2020) revised the best-fit period to 161 days with 36 bursts detected by Effelsberg. This recent activation of FRB121102 gives an additional evidence of the proposed periodicity. We combine the bursts collected in Rajwade et al. (2020) and Cruces et al. (2020) with these newly detected by FAST in 2019 and 2020, and obtain a new best-fit period of ~156.1 days (Figures: see the link at the bottom of the article.) and a duty cycle of about 63.6% (i. e. 99 days turn-on in one putative period). With this putative period, the projected turn-off date is around August 31th - September 9th, 2020. Alternatively, if the source is continuously on after the projected turning-off time, it suggests that the putative period of the source is not real or has evolution. We encourage more follow-up monitoring efforts from other radio observatories. // Reference Chatterjee, S.; Law, C. J.; Wharton, R. S. et al. 2017, Nature, 541, 58 Rajwade, K. M.; Mickaliger, M. B.; Stappers, B. W. et al. 2020, MNRAS, 495, 3551 Cruces, M.; Spitler, L. G.; Scholz, P. 2020arXiv200803461 Marcote, B.; Paragi, Z.; Hessels, J.~W.~T. et al., 2017, ApJL, 834, L8

Phase-Folding MJDs of FRB121102 & fluence as a function of MJD