{
  "bibcode": "2021GCN.30591....1S",
  "body": "B. Sbarufatti (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U.\nLeicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E.\nAmbrosi  (INAF-IASFPA) , D.N. Burrows (PSU), J. D. Gropp (PSU) and P.A.\nEvans (U. Leicester) report on behalf of the Swift-XRT team:\n\nSwift-XRT has performed follow-up observations of the\nFermi/LAT-detected burst GRB 210802A (Longo et al. GCN Circ. 30589) in\na series of observations tiled on the sky. The total exposure time is\n5.2 ks, distributed over 4 tiles; the maximum exposure at a single sky\nlocation was 2.3 ks. The data were collected between T0+41.7 ks and\nT0+43.0 ks, and are entirely in Photon Counting (PC) mode. \n\nTwenty-eight uncatalogued X-ray sources are detected. Many of these\nsources are in the bottom tile (likely a high background effect), and\nin the left tile (possibly an extended emission related to a nearby\ncluster of galaxies). One of the most significant sources (\"Source 7\")\nis above the 2SXPS 3-sigma upper limit at this position, and is\ntherefore likely the GRB afterglow. Using 1246 s of PC mode data and 1\nUVOT image, we find an enhanced XRT position (using the XRT-UVOT\nalignment and matching UVOT field sources to the USNO-B1 catalogue):\nRA, Dec = 230.72285, +29.90180 which is equivalent to:\n\nRA (J2000): 15h 22m 53.48s\nDec(J2000): +29d 54' 06.5\"\n\nwith an uncertainty of 3.5 arcsec (radius, 90% confidence). This\nposition is 9.8 arcmin from the Fermi/LAT position.  While we cannot\ndetermine at the present time whether the source is fading, we note\nthat a previous 1 ks Swift-XRT visit of the field showed no sign of\nSource 7 (https://www.swift.ac.uk/2SXPS/Fields/10000004351).\n\nThe results of the XRT-team automatic analysis of the likely afterglow\nare at https://www.swift.ac.uk/xrt_products/TILED_GRB00100/Source7.php.\n\nThe results of the full analysis of the tiled XRT observations are\navailable at https://www.swift.ac.uk/xrt_products/TILED_GRB00100.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 30591,
  "createdOn": 1628018582000,
  "email": "valerio.delia@ssdc.asi.it",
  "subject": "GRB 210802A: Swift-XRT afterglow detection",
  "submitter": "Valerio D'Elia at ASDC  <valerio.delia@ssdc.asi.it>",
  "eventId": "GRB 210802A"
}