{
  "bibcode": "2021GCN.29859....1M",
  "body": "K. L. Murata, R. Hosokawa, M. Niwano, N. Ito, H. Takamatsu, Y. Yatsu, and\nN.Kawai (TokyoTech) report on behalf of the MITSuME collaboration:\n\nWe observed the field of GRB 210419C (M. J. Moss et al. GCN Circular\n#29834, A.P. Beardmore et al. GCN Circular #29839, WeiKang Zheng and Alexei\nV. Filippenko report on et al. GCN Circular #29840, Simone Leonini et al.\nGCN Circular #29842, Nat Butler et al. GCN Circular #29843, T. Sakamoto et\nal. GCN Circular #29856) with the optical three color (g', Rc, and Ic) CCD\ncameras attached to the MITSuME 50 cm telescope of Akeno Observatory,\nYamanashi, Japan. The observation with a series of 60 sec exposures started\nat 2021-04-20 10:40:08 UT (11.2 hours after the Swift BAT trigger). We\nstacked the images with good conditions. We did not detect any sources\nwithin the enhanced XRT error region (A.P. Beardmore et al. GCN Circular\n#29839) in all three bands. We obtained the 5-sigma limits of the stacked\nimages as follows.\n\nT0+[hour] MID-UT T-EXP[sec] 5-sigma limits\n------------------------------------------------------------------------------------------------\n11.6 11:38 3000 g'>19.6, Rc>19.9, Ic>19.3\n------------------------------------------------------------------------------------------------\nT0+ : Elapsed time after the burst\nT-EXP: Total Exposure time\nWe used the 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": 29859,
  "createdOn": 1618996733000,
  "email": "murata@u.phys.nagoya-u.ac.jp",
  "subject": "GRB 210419C: MITSuME Akeno optical upper limits",
  "submitter": "Katsuhiro L. Murata at Nagoya U  <murata@u.phys.nagoya-u.ac.jp>",
  "eventId": "GRB 210419C"
}