TITLE: GCN CIRCULAR NUMBER: 40756 SUBJECT: EP#01709178975: Swift-XRT counterpart detection DATE: 25/06/17 15:41:32 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 EP#01709178975, collecting 594 s of Photon Counting (PC) mode data between T0+2.1 ks and T0+2.8 ks after the trigger. A candidate counterpart has been found. The details of this source are: Source 1 (SWIFT J154403.9-331113): ================================== RA (J2000.0): 236.0166 = 15h 44m 03.98s Dec (J2000.0): -33.1871 = -33d 11' 13.6" Error: 3.6 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 52 arcsec from the Einstein Probe/WXT position. Mean rate: 1.079 +/- 0.065 ct s^-1 Mean flux: (3.14 +/- 0.19)e-11 erg cm^-2 s^-1 Peak rate: 1.49 +/- 0.24 ct s^-1 Peak flux: (4.32 +/- 0.70)e-11 erg cm^-2 s^-1 ECF: 2.91e-11 erg cm^-2 ct^-1, assuming NH=1.85e+21 cm^-2, gamma=2.42; determined from a spectral fit. This matches a catalogued X-ray source XMMSL3 J154404.2-331108 in the XMM-NEWTON/XMMSLEWCLN catalogue. Details: Separation: 3.0" from the XRT source Cat Rate: 5.9e-01 +/- 2.8e-01 ct s^-1 Cat Flux: 4.6e-12 +/- 2.2e-12 erg cm^-2 s^-1 (0.3-10 keV) so the source is 5.2-sigma above the catalogued flux. There is no evidence for fading. A SIMBAD object `CD-32 11039B' is 3.3" away. There is 1 2MASS object within the source's 3-sigma error radius. We have detected a total of 2 sources. These have been automatically classified as follows: * 0 likely counterparts * 1 candidate counterpart * 1 uncatalogued X-ray source * 0 known X-ray sources Uncatalogued X-ray sources -------------------------- Source 2 (SWIFT J154417.0-331013): ================================== RA (J2000.0): 236.0710 = 15h 44m 17.04s Dec (J2000.0): -33.1705 = -33d 10' 13.8" Error: 10.3 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 2.5 arcmin from the Einstein Probe/WXT position. Mean rate: 0.0122 [+0.0068, -0.0053] ct s^-1 Mean flux: (1.56 [+0.87, -0.67])e-11 erg cm^-2 s^-1 Peak rate: 0.0122 [+0.0068, -0.0053] ct s^-1 Peak flux: (1.56 [+0.87, -0.67])e-11 erg cm^-2 s^-1 ECF: 1.28e-09 erg cm^-2 ct^-1, assuming NH=3.49e+23 cm^-2, gamma=9.92; determined from a spectral fit. XMM UL: 1.8e-12 erg cm^-2 s^-1, (0.3-10 keV) so the source is 1.8-sigma above this 3-sigma upper limit. There is no evidence for fading. A SIMBAD object `UCAC4 285-083088' is 1.7" away. There are 10 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/EP. This circular is an officicial product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40756. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...