{
  "bibcode": "2012GCN.13805....1B",
  "body": "A. A. Breeveld (MSSL-UCL), V. N. Yershov (MSSL-UCL) and N. P. M. Kuin \n(MSSL-UCL) report on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 120923A \n143 s after the BAT trigger (Yershov et al., GCN Circ. 13796).\nNo optical afterglow consistent with the XRT or Gemini position (Goad et \nal., GCN Circ. 13801, Levan et al., GCN Circ. 13802) is detected in the \ninitial UVOT exposure.\nA preliminary 3-sigma upper limit using the UVOT photometric system \n(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding \nchart exposure is:\n\nFilter         T_start(s)   T_stop(s)      Exp(s)         Mag\n\nwhite              143          293          147         >21.3\n\nThe magnitude in the table is not corrected for the Galactic extinction \ndue to the reddening of E(B-V) = 0.16 in the direction of the burst \n(Schlegel et al. 1998).",
  "circularId": 13805,
  "createdOn": 1348404640000,
  "email": "aab@mssl.ucl.ac.uk",
  "subject": "GRB 120923A: Swift/UVOT Upper Limit",
  "submitter": "Alice Breeveld at MSSL-UCL  <aab@mssl.ucl.ac.uk>",
  "eventId": "GRB 120923A"
}