{
  "bibcode": "2022GCN.31889....1M",
  "body": "K. L. Murata, M. Niwano, Y. Imai, N. Ito, Y. Takamatsu, S. Sato, R.\nHosokawa, M. Sasada, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf\nof the MITSuME collaboration:\n\nWe observed the field of GRB 220412B (Gropp et al. GCN Circular #31886)\nwith the optical three color (g', Rc, and Ic) CCD cameras attached to the\nMITSuME 50 cm telescope Akeno. The observation with a series of 60 sec\nexposures started at 2022-04-12 18:28:16 UT (82 minutes after the Swift/BAT\ntrigger). We stacked the images with good conditions. We did not detect any\nuncatalogued sources within the BAT error region (Gropp et al. GCN Circular\n#31886). We obtained the 5-sigma limits of the stacked images as follows.\n\nT0+[min] MID-UT T-EXP[sec] 5-sigma limits\n------------------------------------------------------------------------------------------------\n82 2022-04-12 18:55:21 2820 g'>17.9, Rc>19.0, Ic>18.5\n------------------------------------------------------------------------------------------------\nT0+ : Elapsed time after the burst\nT-EXP: Total Exposure time\nWe used the PS1 catalog for flux calibration. The magnitudes are expressed\nin the AB system. The images were processed in real-time through the\nMITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1,\nPages 4-24; https://github.com/MNiwano/Eclaire).",
  "circularId": 31889,
  "createdOn": 1649828046000,
  "email": "murata@u.phys.nagoya-u.ac.jp",
  "subject": "GRB 220412B: MITSuME Akeno optical upper limits",
  "submitter": "Katsuhiro L. Murata at Nagoya U  <murata@u.phys.nagoya-u.ac.jp>",
  "eventId": "GRB 220412B"
}