{
  "bibcode": "2022GCN.32103....1B",
  "body": "S. Belkin (IKI, HSE), A. Pozanenko (IKI), S. Schmalz (KIAM RAS), A. \nSchmalz (KIAM RAS),  N. Pankov (HSE), Filippo Graziani (GAUSS Srl), \nRiccardo Di Roberto (GAUSS Srl)  report on behalf of IKI GRB FuN:\n\nWe observed  the GRB 220521A (Fermi GBM Team, GCN 32075; Dichiara et \nal., GCN 32076;  Poolakkil and Meegan, GCN 32089) with ORI-22 telescope \nof ISON-Castelgrande observatory. Observation started on 2022-05-21 (UT) \n23:25:00, i.e. 4.65 min after GRB trigger. The series consists of 60 \nimages with an exposure of 60 s in a Clear filter.\n\nThe optical afterglow (Malesani et al., GCN 32078; Fynbo et al., GCN \n32079; Goranskij et al., GCN 32082; Strausbaugh et al., GCN 32091; \nRastinejad et al., GCN 32097) is not detected in the initial part of the \nseries and is marginally detected in the stacked image of the second \npart of the series.\n\nPreliminary photometry of the stacked images is following\n\nDate       UT start   t-T0    Filter Exp.    OT    err     UL(3)\n                      (mid, days)       (s)\n\n2022-05-21 23:25:00   0.012951  Clear 28*60    n/d   n/d   20.5\n2022-05-21 23:57:00   0.035868  Clear 30*60    20.3  0.4   20.2\n\n\nThe photometry is based on nearby USNO-B1.0 (R2) stars\nRA DEC R2\n18:21:04.76880 +10:21:04.7232 16.26\n18:21:07.39800 +10:20:37.5000 16.73",
  "circularId": 32103,
  "createdOn": 1653399083000,
  "email": "apozanen@iki.rssi.ru",
  "subject": "GRB 220521A: ISON-Castelgrande observatory optical observations",
  "submitter": "Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>",
  "eventId": "GRB 220521A"
}