{
  "subject": "GRB 210120A(MASTER OT J105242.66+152355.0 / AT2021axc): Mondy optical observations",
  "eventId": "GRB 210120A",
  "bibcode": "2021GCN.29341....1B",
  "createdOn": 1611220139000,
  "circularId": 29341,
  "submitter": "Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>",
  "email": "apozanen@iki.rssi.ru",
  "body": "S. Belkin (IKI), A. Pozanenko (IKI), N. Pankov (HSE), E. Klunko (ISTP) \nreport  on behalf of GRB IKI FuN:\n\nWe observed the MASTER OT J105242.66+152355.0 / AT2021axc (Lipunov et \nal., GCN 29339) in the field of Fermi GRB 210120A  (Fermi GBM Team, GCN \n29334; Biltzinger et al. GCN 29335) with AZT-33IK telescope of Sayan \nobservatory (Mondy) starting on 2021-01-20 (UT) 20:57:41. The candidate \nin optical afterglow (Lipunov et al., GCN 29339) is well detected in our \nR-filter stacked image at R = 22.14 +/- 0.27 with 3 sigma upper limit of \nthe field for point-like source R=22.3.  We confirm fading nature of the \ntransient and support it for afterglow candidate of GRB 210112A.\n\nPreliminary photometry of the optical transient in the stacked image is \nfollowing\n\nDate       UT start   t-T0       Filter Exp.    OT    Err.  UL(3sigma)\n                       (mid, days)        (s)\n\n2021-01-20 20:57:41   0.59510    R      30*120  22.14 0.27  22.3\n\n\nThe photometry is based on the nearby USNO-B1.0 stars\nUSNO-B1.0_id R2\n1053-0195054 16.13\n1053-0195003 18.57"
}