TITLE: GCN CIRCULAR NUMBER: 32138 SUBJECT: GRB 220527A: MITSuME Akeno optical observation DATE: 22/05/28 02:37:56 GMT FROM: Yuri Imai at Tokyo Inst of Tech Y. Imai, S. Sato, R. Hosokawa, K. L. Murata, M. Sasada, M. Niwano, N. Ito, Y. Takamatsu, M. Tateda, T. Hattori, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We observed the field of GRB 220527A (A. Ursi et al. GCN Circular #32129, The Fermi GBM team et al. GCN Circular #32130, Bissaldi et al. GCN Circular #32131, Evans et al. GCN Circular #32132, Mangan et al. GCN Circular #32133, Sbarufatti et al. GCN Circular #32135, Tohuvavohu et al. GCN Circular #32136,) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope Akeno. The observation with a series of 60 sec exposures started at 2022-05-27 16:05:50 UT (6.8 hours after the AGILE detection). We stacked the images with good conditions. Here we report magnitudes by the forced-photometry at the Swift/XRT position (Sbarufatti et al. GCN Circular #32135). T0+[hour] |MID-UT | T-EXP[sec] | magnitudes of forced-photometry ------------------------------------------------------------------------------------------------ 7.5 | 2022-05-27 16:46:53| 3780 | g'=18.9 +/- 0.2, Rc=18.5 +/- 0.1, Ic=18.3 +/- 0.1 8.7 | 2022-05-27 17:58:38| 3420 | g'=18.9 +/- 0.2, Rc=18.6 +/- 0.1, Ic=18.7 +/- 0.2 ------------------------------------------------------------------------------------------------ T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used PS1 catalog for flux calibration. The magnitudes are expressed in the AB system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1, Pages 4-24; https://github.com/MNiwano/Eclaire).