{
  "bibcode": "2022GCN.32678....1G",
  "body": "P.J. Groot (Radboud/UCT/SAAO), P.M. Vreeswijk (Radboud), R. Ter Horst\n(NOVA), S.D. Bloemen (Radboud), P.G. Jonker (Radboud/SRON), S. de Wet\n(UCT), D.B. Malesani (Radboud and DAWN/NBI), D. Pieterse (Radboud)\nreport on behalf of the BlackGEM consortium:\n\nDuring commissioning the BlackGEM Unit Telescope 3 (BG3-Opal), located\nat ESO La Silla, Chile, observed the optical counterpart of GRB221009A\n(Dichiara et al., GCN 32632, Lesage et al. GCN 32642, Lipunov et al.,\n32634) on 2022-10-11 in a series of 60s exposures in the q,u,z,g,i,r,q\nbands. No debiasing or flatfielding was performed.\n\nThe optical counterpart is detected in q,z,i:\n2022-10-11 00:47UT q = 18.98 +/- 0.09 +/- 0.05 (T0+35h30m)\n2022-10-11 00:50UT z = 16.92 +/- 0.05 +/- 0.03 (T0+35h33m)\n2022-10-11 00:54UT i = 17.92 +/- 0.06 +/- 0.02 (T0+35h37m),\nwhere the first uncertainty is the statistical uncertainty and the\nsecond is the uncertainty on the zeropoint photometric calibration. T0\nis taken as the Fermi/GBM trigger time 2022-10-09 13:17UT (Lesage et\nal., GCN 32642). All magnitudes are in the AB system.\n\nBlackGEM is an array of wide-field telescopes designed, built and\noperated by a consortium consisting of Radboud University, the\nNetherlands Research School for Astronomy NOVA, KU Leuven, the\nUniversity of Manchester, Tel Aviv University, the Weizmann Institute,\nthe Hebrew University of Jerusalem, the University of Potsdam, Texas\nTech University, the University of California at Davis, the Danish\nTechnical University and the Armagh Observatory and Planetarium.",
  "circularId": 32678,
  "createdOn": 1665481653000,
  "email": "p.groot@astro.ru.nl",
  "subject": "GRB 221009A: BlackGEM optical observations",
  "submitter": "Paul Groot at Radboud University Nijmegen  <p.groot@astro.ru.nl>",
  "eventId": "GRB 221009A"
}