{
  "bibcode": "2022GCN.31418....1N",
  "body": "M. Niwano, R. Hosokawa, Y. Imai, K. L. Murata, Y. Takamatsu, N. Ito, R. \nNoto, S. Sato, M. Takaku, R. Yamaguchi, Y. Yatsu, and N. Kawai \n(TokyoTech) report on behalf of the MITSuME collaboration:\n\nWe observed the field of GRB 220107B (M. Arimoto et al. GCN Circular \n#31409, P. A. Evans et al. #31407, J. D. Gropp et al. #31411,�� A. Suresh \net al. #31412, P. Veres and C. Meegan #31414, S.Q. Jiang et al. #31417) \nwith the optical three color (g', Rc, and Ic) CCD cameras attached to \nthe MITSuME 50 cm telescope Akeno. The observation with a series of 60 \nsec exposures started at 2022-01-08 17:04:13 UT (22 hours after Fermi \ntrigger). We stacked the images with good conditions. We did not detect \nany uncatalogued sources within the XRT error region (J. D. Gropp et al. \nGCN Circular #31411). We obtained the 5-sigma limits of the stacked \nimages as follows.\n\nT0+[hours] MID-UT T-EXP[sec] 5-sigma limits\n------------------------------------------------------------------------------------------------ \n\n22.0 2022-01-08 18:58:13 11820 g'>20.7, Rc>20.9, Ic>20.1\n------------------------------------------------------------------------------------------------ \n\nT0+ : Elapsed time after the burst\nT-EXP: Total Exposure time\n\nWe used PS1 catalog for flux calibration.\nThe magnitudes are expressed in the AB system.\nThe images were processed in real-time through the MITSuME GPU reduction \npipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1, Pages 4-24; \nhttps://github.com/MNiwano/Eclaire).",
  "circularId": 31418,
  "createdOn": 1641722063000,
  "email": "niwano@hp.phys.titech.ac.jp",
  "subject": "GRB 220107B: MITSuME Akeno optical upper limits",
  "submitter": "Masafumi Niwano at Tokyo Institute of Tech  <niwano@hp.phys.titech.ac.jp>",
  "eventId": "GRB 220107B"
}