{
  "createdOn": 1757861117765,
  "subject": "GRB 250912A: Swift-XRT observations",
  "bibcode": "2025GCN.41831....1E",
  "circularId": 41831,
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "eventId": "GRB 250912A",
  "submittedHow": "email",
  "body": "P.A. Evans (U. Leicester), J.A. Kennea (PSU), E. Ambrosi  (INAF-IASFPA) , A.P.\nBeardmore (U. Leicester), M.G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), D.N.\nBurrows (PSU), S. Campana (INAF-OAB), M. Capalbi (INAF-OAR), A. D'Ai (INAF-IASFPA),\nP. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), M. Ferro\n(INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester), K.L. Page (U.\nLeicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T. Sbarrato\n(INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf of the\nSwift-XRT team:\n\nSwift-XRT has performed follow-up observations of the SVOM/ECLAIRs-detected source\nGRB 250912A (Ducoin et al., GCN 41820; Wang et al., GCN 41826; see also Fermi GBM\nteam, GCN 41819), collecting 2.2 ks of Photon Counting (PC) mode data between T0+11\nks and T0+55 ks after the trigger. We have detected 1 source.  This has been\nautomatically classified as an uncatalogued X-ray source.\n\nUncatalogued X-ray sources\n--------------------------\n\n  Source 1 (SWIFT J010009.7+111047):\n  ==================================\n    RA (J2000.0):   15.0405  =\t01 00 09.72\n    Dec (J2000.0):  +11.1797  =  +11 10 46.9\n    Error:\t    7.3 (arcsec, radius, 90% confidence).\n    Detect flag:    GOOD\n    Distance:\t    6.8 arcmin from the SVOM/ECLAIRs position.\n    Mean rate:\t    (3.6 [+2.0, -1.5])e-3 ct s^-1\n    Mean flux:\t    (2.7 [+1.5, -1.1])e-13 erg cm^-2 s^-1\n    Peak rate:\t    (3.6 [+2.0, -1.5])e-3 ct s^-1\n    Peak flux:\t    (2.7 [+1.5, -1.1])e-13 erg cm^-2 s^-1\n    ECF:\t    7.43e-11 erg cm^-2 ct^-1\n\t\t      assuming NH=5.11e+20 cm^-2, gamma=0.69\n\t\t      determined from a spectral fit.\n    RASS UL:\t    7.3e-02 ct s^-1 (converted to XRT; 0.3-10 keV)\n\t\t      so the source is not above this 3-sigma upper limit.\n    There is no evidence for fading.\n\nAll fluxes are 0.3-10 keV, observed. For all flux conversions and comparisons with\ncatalogues and upper limits  from other missions, we assumed a power-law spectrum\nwith NH=3x10^20 cm^-2 and photon index (Gamma)=1.7 unless otherwise stated.\n\nWe note that source 1 lies outside the MXT error region reported by Ducoin et al.\n(GCN 41820), so it is likely unrelated with the GRB.\n\nThe results of the XRT-team automatic analysis of the XRT observations, including a\nposition-specific upper limit calculator, are available at\nhttps://www.swift.ac.uk/SVOM/SVOM_FIELD00037.\n\nThis circular is an official product of the Swift-XRT team.\n\n\n"
}