{
  "bibcode": "2010GCN.10704....1A",
  "body": "M. Andreev,  A. Sergeev (Terskol Branch of  Institute of Astronomy),\nA. Volnova (SAI MSU), A. Pozanenko (IKI) report on behalf of larger\nGRB follow-up collaboration:\n\n\nWe observed the field of the Swift GRB 100420A (Baumgartner et al.,\nGCN 10628) with the Z-600 telescope of Mt.Terskol observatory in\nR-filter between (UT) Apr. 20 23:30 - Apr. 21 00:39 under good weather\nconditions with mean seeing of about 1.2 arcsec. We do not detect any\nsource at the position of the enhanced XRT error circle (Beardmore et\nal., GCN 10638).\n\nThe 3 sigma upper limit of the stacked image based on several\nUSNO-B1.0 field stars is following:\n\n\nT0+      Filter,  Exposure,  mag.\n(mid, d)           (s)\n\n0.7789   R       20x180    >20.2",
  "circularId": 10704,
  "createdOn": 1272547710000,
  "email": "alinusss@gmail.com",
  "subject": "GRB 100420A: Terskol optical upper limit",
  "submitter": "Alina Volnova at SAI MSU  <alinusss@gmail.com>",
  "eventId": "GRB 100420A"
}