{
  "submittedHow": "email",
  "circularId": 40079,
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "body": "A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB),\nS. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U.\nLeicester), A.P. Beardmore (U. Leicester) and P.A. Evans (U. Leicester)\nreports on behalf of the Swift-XRT team:\n\nSwift-XRT has conducted further observations of the field of the\nSwift/BAT-detected burst GRB 250331D. The observations now extend from\nT0+45.3 ks to T0+406.9 ks and have a total exposure time of 8.6 ks.\n\nOf the sources previously reported, \"Source 2\" is fading with >3-sigma\nsignificance, and is therefore likely the GRB afterglow. Using 3064 s\nof PC mode data and 2 UVOT images, we find an enhanced XRT position\n(using the XRT-UVOT alignment and matching UVOT field sources to the\nUSNO-B1 catalogue): RA, Dec = 48.65718, +62.28326 which is equivalent\nto:\n\nRA (J2000): 03h 14m 37.72s\nDec(J2000): +62d 16' 59.8\"\n\nwith an uncertainty of 3.5 arcsec (radius, 90% confidence). This\nposition is 3.9 arcmin from the Swift/BAT position.  There is evidence\nthat the source may be fading, however we cannot constrain the decay at\nthe current time.\n\nThe results of the XRT-team automatic analysis of the likely afterglow\nare at https://www.swift.ac.uk/ToO_GRBs/00021825/Source2.php.\nThe results of the full analysis of the XRT observations are available\nat https://www.swift.ac.uk/ToO_GRBs/00021825.\n\nThis circular is an official product of the Swift-XRT team.\n\n",
  "bibcode": "2025GCN.40079....1M",
  "eventId": "GRB 250331D",
  "createdOn": 1743855866080,
  "subject": "GRB 250331D: Swift-XRT afterglow detection"
}