TITLE: GCN CIRCULAR NUMBER: 42461 SUBJECT: GRB 251026A: Swift-XRT observations DATE: 25/10/26 21:42:15 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 251026A (SVOM burst-id sb25102605), collecting 1.7 ks of Photon Counting (PC) mode data between T0+5.8 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 We note that neither source is consistent with the SVOM/MXT position given in GCN Circ. 42454. Uncatalogued X-ray sources -------------------------- Source 1 (SWIFT J044944.9+514605): ================================== RA (J2000.0): 72.4374 = 04 49 44.98 Dec (J2000.0): +51.7683 = +51 46 05.9 Error: 5.1 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 5.8 arcmin from the SVOM/ECLAIRs position. Mean rate: 0.0123 +/- 0.0033 ct s^-1 Mean flux: (4.6 +/- 1.2)e-13 erg cm^-2 s^-1 Peak rate: 0.0123 +/- 0.0033 ct s^-1 Peak flux: (4.6 +/- 1.2)e-13 erg cm^-2 s^-1 ECF: 3.75e-11 erg cm^-2 ct^-1 assuming NH=1.57e+22 cm^-2, gamma=2.98 determined from a spectral fit. XMM UL: 3.5e-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. A SIMBAD object `NVSS J044945+514603' is 7.5" away. There are 2 2MASS objects within the source's 3-sigma error radius. Source 2 (SWIFT J045052.5+515630): ================================== RA (J2000.0): 72.7189 = 04 50 52.54 Dec (J2000.0): +51.9418 = +51 56 30.5 Error: 9.7 (arcsec, radius, 90% confidence). Detect flag: REASONABLE Distance: 9.6 arcmin from the SVOM/ECLAIRs position. Mean rate: (4.0 [+2.6, -1.8])e-3 ct s^-1 Mean flux: (1.74 [+1.10, -0.78])e-13 erg cm^-2 s^-1 Peak rate: (4.0 [+2.6, -1.8])e-3 ct s^-1 Peak flux: (1.74 [+1.10, -0.78])e-13 erg cm^-2 s^-1 XMM UL: 2.3e-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. A SIMBAD object `NVSS J045052+515630' is 3.9" away. There are 6 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_FIELD00045. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42461. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...