TITLE: GCN CIRCULAR NUMBER: 40592 SUBJECT: EP#01709177494: Swift-XRT counterpart detection of known source DATE: 25/05/31 17:47:34 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-IASFPA), 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 EP#01709177494, collecting 2.0 ks of Photon Counting (PC) mode data between T0+388 s and T0+6.2 ks after the trigger. A candidate counterpart has been found. The details of this source are: Source 1 (SWIFT J170930.3-263917): ================================== RA (J2000.0): 257.3766 = 17h 09m 30.38s Dec (J2000.0): -26.6548 = -26d 39' 17.3" Error: 3.5 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 20 arcsec from the Einstein Probe/WXT position. Mean rate: 11.35 +/- 0.22 ct s^-1 Mean flux: (4.665 +/- 0.088)e-10 erg cm^-2 s^-1 Peak rate: 18.7 +/- 3.1 ct s^-1 Peak flux: (7.7 +/- 1.3)e-10 erg cm^-2 s^-1 ECF: 4.11e-11 erg cm^-2 ct^-1, assuming NH=4.40e+21 cm^-2, gamma=1.98; determined from a spectral fit. This matches a catalogued X-ray source LSXPS J170930.1-263918 in the LSXPS catalogue. Details: Separation: 3.2" from the XRT source Cat Rate: 1.2e+00 +/- 9.0e-03 ct s^-1 Cat Flux: 4.7e-11 +/- 3.7e-13 erg cm^-2 s^-1 (0.3-10 keV) so the source is 5.7-sigma above the catalogued flux. There is no evidence for fading. A SIMBAD object `RX J1709.5-2639' is 8.3" away. There is 1 2MASS object 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/EP. This circular is an officicial product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40592. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...