{
  "subject": "GRB 250330A: Swift/UVOT Upper Limits",
  "eventId": "GRB 250330A",
  "submittedHow": "web",
  "bibcode": "2025GCN.39948....1S",
  "createdOn": 1743354945617,
  "submitter": "Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>",
  "circularId": 39948,
  "format": "text/plain",
  "body": "M. H. Siegel (PSU) and S. B. Cenko (GSFC)\nreport on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 250330A\n3944 s after the BAT trigger (Cenko et al., GCN Circ. 39938).\nNo optical afterglow consistent with the XRT position (Osborne et al., GCN\nCirc. 39947) 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\nwhite_FC          3944         4094          147         >21.2\nwhite             3944         4094          147         >21.2\nv                 4101         4300          197         >20.0\nb                 4921         5109          185         >20.9\nu                 4716         4915          197         >20.0\nw1                4511         4711          197         >21.3\nm2                4306         4505          197         >19.8\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.147 in the direction of the burst\n(Schlegel et al. 1998)."
}