{
  "bibcode": "2022GCN.31413....1H",
  "body": "R. Hosokawa, Y. Imai, M. Niwano, K. L. Murata, N. Ito, Y. Takamatsu,\nM. Takaku, R. Noto, S. Sato, R. Yamaguchi, Y. Yatsu, and N. Kawai\n(TokyoTech) report on behalf of the MITSuME collaboration:\n\nWe observed the field of GRB 220107A (The Fermi GBM team et al. GCN\nCircular #31399, F. Kunzweiler et al. GCN Circular #31400, James\nDeLaunay et al. GCN Circular #31402, V. Lipunov et al. GCN Circular\n#31403, P. A. Evans et al. GCN Circular #31404, P. Veres et al. GCN\nCircular #31406, A. Suresh et al. GCN Circular #31408, D.N. Burrows et\nal. GCN Circular #31410) with the optical three color (g', Rc, and Ic)\nCCD cameras attached to the MITSuME 50 cm telescope Akeno. The\nobservation with a series of 60 sec exposures was carried out from\n2022-01-07 20:21:55 UT (~5.6 hours after the Fermi GBM trigger). We\nstacked the images with good conditions.\n\nOur observation covered 100% of the Swift/BAT-GUANO error region\n(James DeLaunay et al. GCN Circular #31402). Comparing our co-added\nimages with the GSC2.3 and PS1 catalog, we marginally detected one\nuncatalogued source at RA, Dec = (169.80774, 34.17079), which is\nequivalent to:\nRA (J2000): 11h19m13.859s\nDec(J2000): +34d 10' 14.845\"\nThis position is 4.4 arcsec from the center of Swift XRT position\n(D.N. Burrows et al. GCN Circular #31410).\nThe magnitudes of the source are as follows.\n\nT0+[hour] | MID-UT | T-EXP[sec] | candidate magnitude | 5-sigma limits\n------------------------------------------------------------------------------------------------\n5.4 | 2022-01-07 20:55:27 | 1620 | g'=19.8 +/- 0.5, Rc=18.9 +/- 0.2,\nIc=18.3 +/- 0.2 | g'>20.9, Rc>21.0, Ic>20.3\n------------------------------------------------------------------------------------------------\nT0+ : Elapsed time after the burst\nT-EXP: Total Exposure time\n\nWe used PS1 catalog for flux calibration. The conversion from PS1 r\nand i band to our Rc and Ic band is by the equation of Tonry et al.\n(2012), Table. 6. The magnitudes are expressed in the AB system. The\nimages 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": 31413,
  "createdOn": 1641652852000,
  "email": "hosokawa@hp.phys.titech.ac.jp",
  "subject": "GRB 220107A: MITSuME Akeno optical observation",
  "submitter": "Ryohei Hosokawa at Tokyo Institute of Technology  <hosokawa@hp.phys.titech.ac.jp>",
  "eventId": "GRB 220107A"
}