{
  "bibcode": "2021GCN.29286....1B",
  "body": "S. Belkin (IKI), A. Pozanenko (IKI),  E. Klunko (ISTP), V. Kim (FAI, \nPulkovo Observatory), Y. Aimuratov (FAI), M. Krugov (FAI) report on \nbehalf of GRB IKI FuN:\n\nWe observed  GRB 210104A (Fermi GBM team, GCN 29232; Troja et al., GCN \n29233; Frederiks et al., GCN  29258; Cherry et al., GCN 29268) with \nAZT-33IK telescope of Sayan observatory (Mondy).   We detect the optical \nafterglow (Troja et al., GCN 29233; Xin et al., GCN 29235; Hu et al., \nGCN 29236; Hosokawa et al., GCN  29237; Kim et al., GCN 29238, 29265; \nLipunov et al., GCN 29239; Horiuchi et al., GCN 29241; Breeveld et al., \nGCN 29247; Zhu et al., GCN 29252; Paek  et al., GCN 29254; Kumar et al., \nGCN 29257; Smartt et al., GCN 29262; Romanov, GCN 29269; Anandagoda et \nal., GCN 29273; Gokuldass, GCN 29274; Mao et al.,  GCN 29275; Moskvitin \net al., GCN 29277).\n\nPreliminary photometry of the afterglow  is following\n\nDate       UT start   t-T0     Filter Exp.   OT       Err. UL(3 sigma)\n                       (mid, days)     (s)\n\n2021-01-07 15:10:23   3.19681  R      80*90   n/d     n/d 22.1\n2021-01-08 15:22:18   4.20438  R      59*120  22.2    0.2 22.9\n2021-01-09 11:51:54   5.07980  R      90*120  22.7    0.3 22.7\n\n\nThe photometry is based on nearby stars of  USNO-B1.0\nUSNO-B1.0_id R2\n1546-0139059 15.53\n1546-0139029 14.82\n\nA light curve of the afterglow based on our observations including \nreported early (Kim et al., GCN 29238, 29265, 29283) can be found in\n\nhttp://grb.rssi.ru/GRB210104A/GRB210104A_LC.png",
  "circularId": 29286,
  "createdOn": 1610318087000,
  "email": "apozanen@iki.rssi.ru",
  "subject": "GRB 210104A: Mondy optical observations, light curve",
  "submitter": "Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>",
  "eventId": "GRB 210104A"
}