{
  "body": "M. H. Siegel (PSU) and T. M. Parsotan (GSFC) report on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 250327A 13.8 ks after the BAT trigger (Parsotan et al., GCN Circ. 39877). No optical afterglow consistent with the XRT position (Burrows et al., GCN Circ. 39892) GCN Circ. 39977) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are:\n\nFilter         T_start(s)   T_stop(s)      Exp(s)         Mag\n\nB                25500        43748         1714            >20.88\nUVM2             47869        48769          885            >20.28\nU                14704        42891         1711            >20.58\nV                21282        21402          117            >18.30\nUVW1             13797        49176         1885            >20.62\nUVW2             20376        21275          885            >20.31\nWHITE            26413        27065          633            >20.81\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.053 in the direction of the burst\n(Schlegel et al. 1998).",
  "circularId": 40008,
  "submitter": "Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>",
  "subject": "GRB 250327A: Swift/UVOT Upper Limits",
  "submittedHow": "web",
  "bibcode": "2025GCN.40008....1S",
  "format": "text/plain",
  "eventId": "GRB 250327A",
  "createdOn": 1743599288044
}