{
  "bibcode": "2021GCN.29255....1K",
  "body": "V. Kim (FAI, Pulkovo), I. Reva (FAI), M. Krugov (FAI), Y. Aimuratov \n(FAI) report:\n\nWe observed the field of GRB 210104B (Laha et al., GCN 29243) with \nAZT-20 1.5-m telescope\nof Assy-Turgen Observatory (Assy) starting on Jan. 04 (UT) 22:31:15.\nWe did not find any optical counterpart in our 20x60s stacked image in \nthe enhanced\nXRT position (Evans et al., GCN 29253) down to an upper limit R~23.2\n(see also Hu et al., GCN 29249 and Fu et al., GCN 29250).\nPreliminary photometry of the filed is the following:\n\nDate        UT start  t-T0         Filter  Exp.    OT    Err.  \nUL(3-sigma) FWHM\n                       (mid, days)          (s)                           \n   (\")\n2021-01-04  22:31:15  0.06325      r'      20*60   n/d   n/d   23.2      \n   2.3\n\nFurther observations on this object are not planned except personal \nrequest.",
  "circularId": 29255,
  "createdOn": 1609835660000,
  "email": "aimuratov@aphi.kz",
  "subject": "GRB 210104B: Assy optical upper limit",
  "submitter": "Yerlan Aimuratov at Fesenkov Astrophysical Inst.(FAI)  <aimuratov@aphi.kz>",
  "eventId": "GRB 210104B"
}