{
  "bibcode": "2018GCN.22611....1S",
  "body": "M. H. Siegel (PSU) and S. J. LaPorte (PSU)\nreport on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 180404B\n82 s after the BAT trigger (LaPorte et al., GCN Circ. 22590).\nA fading source consistent with the XRT position\n(Beardmore et al. GCN Circ. 22594)\nis detected in the initial UVOT exposures.\n\nThe preliminary UVOT position is:\n   RA  (J2000) =  03:33:34.23 =  53.39262 (deg.)\n   Dec (J2000) = -50:12:54.2  = -50.21506 (deg.)\nwith an estimated uncertainty of 0.46 arc sec. (radius, 90% confidence).\n\nPreliminary detections and 3-sigma upper limits using the UVOT photometric system\n(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: \n\nFilter         T_start(s)   T_stop(s)      Exp(s)           Mag\n\nwhite (fc)          82          231          147         18.66 +/- 0.09\nwhite               82         1720          411         19.39 +/- 0.09\nwhite             6421         6620          196        >20.7\nv                  624         7031          510        >19.5\nb                  550         7661          322        >20.3\nu (fc)             295          545          245         19.49 +/- 0.31\nu                  295         1670          343         19.70 +/- 0.29\nu                 6011         7648          393        >20.1\nw1                 674         7442          510        >20.6\nm2                1600         7236          413        >20.5\nw2                 600         6826          452        >20.2\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.01 in the direction of the burst\n(Schlegel et al. 1998).",
  "circularId": 22611,
  "createdOn": 1523038446000,
  "email": "siegel@swift.psu.edu",
  "subject": "GRB 180404B: Swift/UVOT Detection",
  "submitter": "Mike Siegel at PSU/Swift MOC  <siegel@swift.psu.edu>",
  "eventId": "GRB 180404B"
}