{
  "bibcode": "2017GCN.20851....1S",
  "body": "M. H. Siegel (PSU) and J. R. Cummings (NASA/UMBC)\nreport on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 170311A\n110 s after the BAT trigger (Cummings et al., GCN Circ. 20846).\nNo optical afterglow consistent with the XRT position\n(Cummings et al. GCN Circ. 20846)\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           110          259          147         >20.5\nu_FC               269          519          246         >19.7\nwhite              110         7074          645         >21.2\nv                  600        11424         1022         >20.3\nb                  525         5585          294         >20.1\nu                  269         5380          537         >20.1\nw1                 650         5175          279         >20.1\nm2                 624        13058           82         >20.1\nw2                 575         7280          313         >20.2\n\nThe magnitudes in the table are 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": 20851,
  "createdOn": 1489284646000,
  "email": "siegel@swift.psu.edu",
  "subject": "GRB 170311A: Swift/UVOT Upper Limits",
  "submitter": "Mike Siegel at PSU/Swift MOC  <siegel@swift.psu.edu>",
  "eventId": "GRB 170311A"
}