{
  "createdOn": 1755098144313,
  "circularId": 41344,
  "format": "text/plain",
  "submitter": "Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>",
  "bibcode": "2025GCN.41344....1S",
  "subject": "GRB 250812A: Swift/UVOT Detection",
  "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 250812A 6.5 ks after the SVOM/ECLAIRs trigger (Xin et al., GCN Circ. 41322). An uncatalogued source consistent with the XRT position (Sbarrato et al., GCN Circ. 41325) and the optical transient (He et al., GCN Circ. 41324; Xin et al., GCN Circ. 41326; Rakotondrainibe et al., GCN Circ. 41328; Freeberg et al., GCN Circ. 41333) is detected in the UVOT exposures. However, we note that the source shows no evidence of fading in the 67 ks between the two Swift epochs.\n\nThe preliminary UVOT position is:\n    RA  (J2000) =  02:11:13.68 =  32.80701 (deg.)\n    Dec (J2000) = -43:09:49.1  = -43.16363 (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\nu                 6500        12380         1479      19.43+/-0.12\nu                73801        90784          695      19.48+/-0.13\nv                74444        91365          424            >19.24\nwhite            74122        91182          695      19.96+/-0.10\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.012 in the direction of the burst\n(Schlegel et al. 1998).",
  "submittedHow": "web",
  "eventId": "GRB 250812A"
}