{
  "bibcode": "2012GCN.13047....1B",
  "body": "A. A. Breeveld (MSSL-UCL) and F. E. Marshall (NASA/GSFC)\nreport on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 120311B\n3072 s after the BAT trigger (Marshall et al., GCN Circ. 13038).\nNo optical afterglow consistent with the XRT position (Osborne et al., \nGCN Circ. 13042) is 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          3072         3222          147         >21.4\nwhite             3072        16503         2114         >22.8\nv                 3228        21300         2013         >20.3\nb                 4048        15591         1233         >20.7\nu                 3843         5479          393         >19.7\nw1                3638        22969         1136         >20.9\nm2                3433        22206         1082         >20.8\nw2                4460        17192         1754         >21.9\n\nThe magnitudes in the table are not corrected for the Galactic \nextinction due to the reddening of E(B-V) = 0.52 in the direction of the \nburst (Schlegel et al. 1998).",
  "circularId": 13047,
  "createdOn": 1331554509000,
  "email": "aab@mssl.ucl.ac.uk",
  "subject": "GRB 120311B: Swift/UVOT Upper Limits",
  "submitter": "Alice Breeveld at MSSL-UCL  <aab@mssl.ucl.ac.uk>",
  "eventId": "GRB 120311B"
}