{
  "bibcode": "2020GCN.27268....1K",
  "body": "N. P. M. Kuin (UCL-MSSL) and S. L. Laha (GSFC/UMBC/CRESST)\nreport on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 200228B\n137 s after the BAT trigger (Laha et al., GCN Circ. 27254).  No optical\nafterglow consistent with the XRT position (Evans et al., GCN Circ.\n #27256 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\nu_FC               137          387          246         >20.1\nv                 4992        10685          676         >20.1\nb                 4580         6012          393         >20.6\nu                  137         5807          442         >20.4\nw1                5402         5602          197         >19.5\nm2                5197         5396          197         >19.8\nw2                4786         6218          393         >19.4\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.092 in the direction of the burst\n(Schlegel et al. 1998).",
  "circularId": 27268,
  "createdOn": 1582928612000,
  "email": "npkuin@gmail.com",
  "subject": "GRB 200228B: Swift/UVOT Upper Limits",
  "submitter": "Paul Kuin at MSSL  <npkuin@gmail.com>",
  "eventId": "GRB 200228B"
}