{
  "bibcode": "2017GCN.20508....1G",
  "body": "C. Guidorzi (U. Ferrara), S. Kobayashi, I.A. Steele (LJMU), A. Gomboc \n(U. Nova Gorica), C.G. Mundell (U. Bath) on behalf of a large \ncollaboration report:\n\nWe observed Fermi GRB 170121B (Hamburg et al. GCN 20505) on January 23, \n07:21 UT (1.7 days since the GRB) with the 2-m LCO Faulkes Telescope \nNorth in Hawaii with SDSS r and i filters. We do not detect the MASTER \noptical counterpart (Lipunov et al. GCN 20502) down to the following limits:\n\nMid Time      Exposure       Filter       Magnitude (AB)\n(days)           (s)\n-------------------------------------------------------\n1.69            2x120        SDSS-R        > 21.0\n1.69            2x120        SDSS-I        > 19.5\n-------------------------------------------------------\n\nas calibrated against nearby USNO-URAT1 sources.",
  "circularId": 20508,
  "createdOn": 1485160914000,
  "email": "guidorzi@fe.infn.it",
  "subject": "GRB 170121B: LCO FTN observations",
  "submitter": "Cristiano Guidorzi at Ferrara U,Italy  <guidorzi@fe.infn.it>",
  "eventId": "GRB 170121B"
}