Optical Rebrightening of MAXI J1820+070 = ASASSN-18ey

ATel #13502; R. Adachi, K. L. Murata, M. Oeda, M. Niwano, K. Shiraishi, K. Iida, F. Ogawa, R. Hosokawa, N. Nakamura, S. Toma, Y. Yatsu, and N. Kawai (TokyoTech) report on behalf of the MITSuME collaboration
on 19 Feb 2020; 11:47 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Katsuhiro Murata (murata@hp.phys.titech.ac.jp)

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We have been monitoring the black hole X-ray binary MAXI J1820+070 = ASASSN-18ey (ATel #11399, #11400, #12567, #12573, #13014, #13025 and others) since Jan. 18, 2020 with the MITSuME 50 cm Telescope at Akeno Observatory, Yamanashi, Japan, in the optical three colors (g', Rc, and Ic). We found the brightening of the object on Feb. 18, suggesting the onset of the third rebrightening of this object after its main outburst in 2018. The last optical outburst (the second rebrightening) started on early August 2019 (ATel #13014) and reached its optical peak in about ten days, with the total duration of about 70 days. We obtained the preliminary magnitudes of MAXI J1820+070 as follows: g'=18.5 +/-0.3, Rc=17.9+/-0.1, Ic=16.9+/-0.1 on 2020-02-14 (MJD 58893.81), and g'=17.0+/-0.1, Rc=16.4+/-0.1, Ic=15.9+/-0.1 on 2020-02-18 (MJD 58897.80). We will continue simultaneous multi-color observation with the MITSuME telescope. Multiwavelength follow-up observations are strongly encouraged.