TITLE: GCN CIRCULAR NUMBER: 41698 SUBJECT: EP250903a: Swift-XRT observations DATE: 25/09/04 13:34:42 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 Einstein Probe/WXT-detected source EP250903a, collecting 3.7 ks of Photon Counting (PC) mode data between T0+1.3 ks and T0+35 ks after the trigger. We have detected 1 source inside the EP/WXT error region. This has been automatically classified as follows: * 0 likely counterparts * 0 candidate counterparts * 1 uncatalogued X-ray source * 0 known X-ray sources Uncatalogued X-ray sources -------------------------- Source 2 (SWIFT J223627.0-495113): ================================== RA (J2000.0): 339.1126 = 22 36 27.02 Dec (J2000.0): -49.8538 = -49 51 13.7 Error: 7.1 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 37 arcsec from the Einstein Probe/WXT position. Mean rate: (3.8 [+1.4, -1.2])e-3 ct s^-1 Mean flux: (2.20 [+0.83, -0.67])e-13 erg cm^-2 s^-1 Peak rate: (3.8 [+1.4, -1.2])e-3 ct s^-1 Peak flux: (2.20 [+0.83, -0.67])e-13 erg cm^-2 s^-1 ECF: 5.78e-11 erg cm^-2 ct^-1 assuming NH=1.17e+20 cm^-2, gamma=1.15 determined from a spectral fit. XMM UL: 1.9e-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 2 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 position of Source 2 is consistent with the optical counterpart detected by LCO (GCN 41680) and SVOM/VT (GCN 41683). 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/EP/EP_FIELD00068. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41698. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...