{
  "eventId": "GRB 250910A",
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "circularId": 41799,
  "bibcode": "2025GCN.41799....1L",
  "subject": "GRB 250910A / EP250910a: Swift-XRT afterglow detection",
  "body": "S. Lanava (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne (U.\nLeicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), M.\nPerri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti\n(INAF-OAB) and P.A. Evans (U. Leicester) reports on behalf of the\nSwift-XRT team:\n\nSwift-XRT has performed follow-up observations of GRB 250910A. We\nsearched for X-ray sources in  1.2 ks of Photon Counting (PC) mode\ndata. The total exposure at the position of the afterglow (see below)\nis 1.2 ks, obtained between T0+29.5 ks and T0+30.7 ks.\n\nAn uncatalogued X-ray source is detected and is believed to be the\nafterglow. Using 1195 s of PC mode data and 1 UVOT image, we find an\nenhanced XRT position (using the XRT-UVOT alignment and matching UVOT\nfield sources to the USNO-B1 catalogue): RA, Dec = 39.80164, -39.69498\nwhich is equivalent to:\n\nRA (J2000): 02h 39m 12.39s\nDec(J2000): -39d 41' 41.9\"\n\nwith an uncertainty of 8.4 arcsec (radius, 90% confidence). This source\nis consistent with the position reported by EP/FXT (Liu et al., GCN\n41776) and with the optical/NIR source detected with VLT (Schneider et\nal., GCN 41794) and SVOM/VT (Li et al., GCN 41798). We cannot determine\nat the present time whether the source is fading.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/03000083.\nThe results of the full analysis of the XRT observations are available\nat https://www.swift.ac.uk/SVOM/SVOM_FIELD00036.\n\nThis circular is an official product of the Swift-XRT team.\n\n",
  "submittedHow": "email",
  "createdOn": 1757608192896
}