{
  "bibcode": "2012GCN.12891....1M",
  "body": "F. E. Marshall (NASA/GSFC) and K. L. Page (U. Leicester)\nreport on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 120121A\n124 s after the BAT trigger (Page et al., GCN Circ. 12885).\nNo optical afterglow consistent with the XRT position\n(Evans et al., GCN Circ. 12888)\nis detected in the initial UVOT exposures.\nPreliminary 3-sigma upper limits using the UVOT photometric system\n(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first\nfinding chart (FC) exposure and subsequent exposures are:\n\nFilter         T_start(s)   T_stop(s)      Exp(s)         Mag\n\nwhite_FC           124          273          147         >20.2\nu_FC               336          585          246         >19.7\nwhite              124         6777          673         >21.1\nv                  664         7188          510         >18.9\nb                  591        13219         1160         >20.2\nu                  336        18998         2078         >20.2\nw1                 714        18281         2108         >20.4\nm2               16474        17374          886         >20.1\nw2                1020        23198         1298         >21.1\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.87 in the direction of the burst\n(Schlegel et al. 1998).",
  "circularId": 12891,
  "createdOn": 1327176684000,
  "email": "femarsha@khamseen.gsfc.nasa.gov",
  "subject": "GRB 120121A: Swift/UVOT Upper Limits",
  "submitter": "Frank Marshall at GSFC  <femarsha@khamseen.gsfc.nasa.gov>",
  "eventId": "GRB 120121A"
}