{
  "bibcode": "2011GCN.11955....1O",
  "body": "S. R. Oates (MSSL-UCL) & B. Sbarufatti (INAF-OAB/IASFPA) report on behalf of the Swift-UVOT team\n\nThe Swift/UVOT began settled observations of the field of GRB 110420B\n2562 s after the BAT trigger (Sbarufatti et al., GCN Circ. 11944).\nNo optical afterglow is found within the BAT error circle.\n\nPreliminary 3-sigma upper limits using the UVOT photometric system\n(Poole et al. 2008, MNRAS, 383, 627) for the first finding chart (FC)\nexposure and subsequent exposures are:\n\nFilter         T_start(s)   T_stop(s)      Exp(s)         Mag\n###############################################################\nwhite_FC          2562         2711          147         >20.6\nwhite             2562         4765          540         >20.5\nv                 3541        16124         1322         >19.9\nb                 2926        22368          621         >20.4\nu                 2720        28151         1730         >20.0\nw1                3950        28007         2844         >19.6\nm2                3745        27103         2416         >19.5\nw2                3336        15211         1279         >19.7\n###############################################################\n\nThe values quoted above are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.03 in the direction of the burst\n(Schlegel et al. 1998).",
  "circularId": 11955,
  "createdOn": 1303396196000,
  "email": "sro@mssl.ucl.ac.uk",
  "subject": "GRB 110420B: Swift/UVOT Upper Limits",
  "submitter": "Samantha Oates at MSSL  <sro@mssl.ucl.ac.uk>",
  "eventId": "GRB 110420B"
}