{
  "bibcode": "2011GCN.12438....1V",
  "body": "A. Volnova (SAI MSU), A. Pozanenko (IKI), E. Klunko (ISTP), V. Rumyantsev \n(CrAO),  N.Pit (CrAO) on behalf of  larger GRB follow up collaboration \nreport:\n\nWe observed  the field of the Swift GRB 110921A (Baumgartner et al., GCN \n12373) with  AZT-33IK telescope of Sayan observatory (Mondy) on Sep. 21 \nbetween (UT) 14:36:31 -- 16:05:00 and AZT-11 telescope of CrAO  on Sep. 21 \nbetween (UT) 17:38:46 -- 19:00:15. In a combined image of a few first frames \ntaken with AZT-33IK we detected a faint source which coincides with the \noptical counterpart of  GRB 110921A (Xin et al., GCN 12377; Xu et al., GCN \n12385).   A photometry  is based on the  star USNO B1.0 1263-0338839 (19 36 \n21.52 +36 19 56.2) assuming R=16.13\n\nT0+,       Filter,  Exposure, OT,  UL(3 sigma), Telescope\n(mid, d)             (s)\n\n0.03934 R 850  22.08 +/- 0.18  22.3    AZT-33IK\n0.07558 R 1920 n/d                   22.5    AZT-33IK\n0.18620 R 4860 n/d                   21.3    AZT-11\n\nIn a combined image of a total exposure of 3030 s taken with AZT-33IK \ntelescope we clearly detected the SDSS object noted by Xu et al. (GCN 12385) \nand Vreeswijk et al. (GCN 12387). The photometry of the SDSS object against \nthe above calibration star is R=22.8 +/- 0.3.",
  "circularId": 12438,
  "createdOn": 1318728338000,
  "email": "apozanen@iki.rssi.ru",
  "subject": "GRB 110921A: optical observations",
  "submitter": "Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>",
  "eventId": "GRB 110921A"
}