{
  "bibcode": "2021GCN.30220....1N",
  "body": "R. Noto, R. Hosokawa, K. L. Murata, M. Niwano, N. Ito, H. Takamatsu,\nY. Imai, 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 210610B (Page et al. GCN #30170, Ursi et\nal. GCN #30195, Frederiks et al. GCN #30196, Malacaria et al. GCN\n#30199) with the optical three color (g', Rc, and Ic) CCD cameras\nattached to the MITSuME 50 cm telescope Akeno. The observation with a\nseries of 60 sec exposures started at 2021-06-11 10:33:20 UT (14.7\nhours after Swift BAT trigger). We stacked the images with good\nconditions. We detected the afterglow reported previously (Page et al.\nGCN #30170, Kumar et al. GCN #30174, Rumyantsev et al. GCN #30175,\nLipunov et al. GCN #30176, Hu et al. GCN #30177, Rumyantsev et al. GCN\n#30178, Wet et al. GCN #30180, Romanov et al. GCN #30181, Fynbo et al.\nGCN #30182, Moskvitin et al. GCN #30187, Becerra et al. GCN #30190,\nMong et al. GCN #30193, Postigo et al. GCN #30194, Marchini et al. GCN\n#30198, Dutta et al. GCN #30201, Zheng et al. GCN #30204, Vreeswijk et\nal. GCN #30205, Perley et al. GCN #30206, Pankov et al. GCN #30212,\nPankov et al. GCN #30215, Perley et al. GCN #30216, Laskar et al. GCN\n#30217, Alexander et al. GCN #30218)\n\nWe measured the magnitudes as follows.\nMID-UT T-EXP[sec] measured magnitudes\n------------------------------------------------------------------------------------------------\n2021-06-11 12:51:05 9780 g'=19.3+/-0.2, Rc=18.9+/-0.1, Ic=18.8+/-0.1\n------------------------------------------------------------------------------------------------\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\nreduction pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1, Pages\n4-24; https://github.com/MNiwano/Eclaire).",
  "circularId": 30220,
  "createdOn": 1623478758000,
  "email": "hosokawa@hp.phys.titech.ac.jp",
  "subject": "GRB 210610B: MITSuME Akeno optical observation",
  "submitter": "Ryohei Hosokawa at Tokyo Institute of Technology  <hosokawa@hp.phys.titech.ac.jp>",
  "eventId": "GRB 210610B"
}