TITLE: GCN CIRCULAR NUMBER: 42486 SUBJECT: GRB 251027A: Swift-XRT observations DATE: 25/10/27 16:36:26 GMT FROM: Phil Evans at U of Leicester <pae9@star.le.ac.uk> P.A. Evans (U. Leicester), J.A. Kennea (PSU), E. Ambrosi (INAF-IASFPA) , A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), D.N. Burrows (PSU), S. Campana (INAF-OAB), M. Capalbi (INAF-OAR), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), M. Ferro (INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the SVOM/ECLAIRs-detected source GRB 251027A, collecting 1.6 ks of Photon Counting (PC) mode data between T0+4.5 ks and T0+12 ks after the trigger. We have detected 2 sources. These have been automatically classified as follows: * 0 likely counterparts * 0 candidate counterparts * 2 uncatalogued X-ray sources * 0 known X-ray sources Uncatalogued X-ray sources -------------------------- Source 1 (SWIFT J062052.1+114644): ================================== RA (J2000.0): 95.2175 = 06 20 52.20 Dec (J2000.0): +11.7792 = +11 46 45.1 Error: 7.5 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 5.8 arcmin from the SVOM/ECLAIRs position. Mean rate: (5.4 [+2.7, -2.0])e-3 ct s^-1 Mean flux: (1.90 [+0.95, -0.72])e-10 erg cm^-2 s^-1 Peak rate: (5.4 [+2.7, -2.0])e-3 ct s^-1 Peak flux: (1.90 [+0.95, -0.72])e-10 erg cm^-2 s^-1 ECF: 3.52e-08 erg cm^-2 ct^-1 assuming NH=1.86e+24 cm^-2, gamma=-3.00 determined from a spectral fit. XMM UL: 2.1e-12 erg cm^-2 s^-1, (0.3-10 keV) so the source is 2.2-sigma above this 3-sigma upper limit. There is no evidence for fading. A SIMBAD object `NVSS J062052+114645' is 0.1" away. There are 4 2MASS objects within the source's 3-sigma error radius. Source 3 (SWIFT J062105.2+112959): ================================== RA (J2000.0): 95.2720 = 06 21 05.28 Dec (J2000.0): +11.4998 = +11 29 59.3 Error: 8.8 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 12.3 arcmin from the SVOM/ECLAIRs position. Mean rate: (5.7 [+3.5, -2.5])e-3 ct s^-1 Mean flux: (2.4 [+1.5, -1.1])e-13 erg cm^-2 s^-1 Peak rate: (5.7 [+3.5, -2.5])e-3 ct s^-1 Peak flux: (2.4 [+1.5, -1.1])e-13 erg cm^-2 s^-1 XMM UL: 3.3e-12 erg cm^-2 s^-1, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. There are 5 2MASS objects within the source's 3-sigma error radius. All fluxes are 0.3-10 keV, observed. For all flux conversions and comparisons with catalogues and upper limits from other missions, we assumed a power-law spectrum with NH=3x10^20 cm^-2 and photon index (Gamma)=1.7 unless otherwise stated. The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/SVOM/SVOM_FIELD00046. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42486. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...