{
  "circularId": 42299,
  "submitter": "Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>",
  "submittedHow": "web",
  "format": "text/plain",
  "createdOn": 1760559603172,
  "body": "M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 251013D 71 ks after the Fermi/GBM trigger (GCN Circ. 42224; DeLaunay et al., GCN Circ. 42244). We detect an uncatalogued optical source near the position of XRT source #2 (Burrows et al., GCN Circ. 42291). There is no evidence of fading in the UVOT data thus far.\n\nThe preliminary UVOT position is:\n    RA  (J2000) =  03:07:52.73 =  46.96971 (deg.)\n    Dec (J2000) = +08:48:57.4  =   8.81595 (deg.)\nwith an estimated uncertainty of 0.42 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            71081        72734         1622      20.98+/-0.16\nwhite            76655        78444         1758      20.78+/-0.13\nwhite            82245        83695         1423      20.68+/-0.13\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.312 in the direction of the burst\n(Schlegel et al. 1998).",
  "subject": "GRB 251013D: Swift/UVOT Observations",
  "bibcode": "2025GCN.42299....1S",
  "eventId": "GRB 251013D"
}