TITLE: GCN CIRCULAR NUMBER: 41401 SUBJECT: sb25081602: Swift-XRT observations DATE: 25/08/17 11:56:08 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 sb25081602, collecting 1.7 ks of Photon Counting (PC) mode data between T0+1.8 ks and T0+7.3 ks after the trigger. We have detected 2 sources. These have been automatically classified as follows: * 0 likely counterparts * 0 candidate counterparts * 0 uncatalogued X-ray sources * 2 known X-ray sources

Known X-ray sources -------------------

Source 1 (SWIFT J051406.2-400234): ================================== RA (J2000.0): 78.5261 = 05h 14m 06.26s Dec (J2000.0): -40.0430 = -40d 02' 34.8" Error: 3.5 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 3.7 arcmin from the SVOM/ECLAIRs position. Mean rate: 3.58 +/- 0.14 ct s^-1 Mean flux: (1.474 +/- 0.058)e-10 erg cm^-2 s^-1 Peak rate: 6.7 +/- 1.5 ct s^-1 Peak flux: (2.75 +/- 0.62)e-10 erg cm^-2 s^-1 ECF: 4.11e-11 erg cm^-2 ct^-1 assuming NH=9.61e+20 cm^-2, gamma=1.65 determined from a spectral fit. This matches a catalogued X-ray source LSXPS J051406.5-400237 in the LSXPS catalogue. Details: Separation: 4.4" from the XRT source Cat Rate: 5.0e+00 +/- 2.1e-02 ct s^-1 Cat Flux: 2.1e-10 +/- 8.6e-13 erg cm^-2 s^-1 (0.3-10 keV) so the source is 1.1-sigma above the catalogued flux. There is no evidence for fading. This is 3.05" from the SIMBAD position of 4U 0513-40, noted by Magnani et al. (GCN Circ. 41399). There are 10 2MASS objects within the source's 3-sigma error radius.

Source 2 (SWIFT J051413.9-395933): ================================== RA (J2000.0): 78.5583 = 05h 14m 13.99s Dec (J2000.0): -39.9927 = -39d 59' 33.7" Error: 5.8 (arcsec, radius, 90% confidence). Detect flag: REASONABLE Distance: 2.1 arcmin from the SVOM/ECLAIRs position. Mean rate: (-1.0 +/- -1.0)e0 ct s^-1 Mean flux: (-2.2 +/- -2.2)e-11 erg cm^-2 s^-1 Peak rate: (4.5 [+2.6, -2.1])e-3 ct s^-1 Peak flux: (9.6 [+5.6, -4.4])e-14 erg cm^-2 s^-1 ECF: 2.16e-11 erg cm^-2 ct^-1 assuming NH=1.21e+22 cm^-2, gamma=9.85 determined from a spectral fit. This matches a catalogued X-ray source LSXPS J051414.3-395936 in the LSXPS catalogue. Details: Separation: 4.6" from the XRT source Cat Rate: 0.0e+00 +/- 2.3e-04 ct s^-1 Cat Flux: 0.0e+00 +/- 5.1e-15 erg cm^-2 s^-1 (0.3-10 keV) so the source is 1.9-sigma above the catalogued flux. There is no evidence for fading.

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_FIELD00030.

This circular is an official product of the Swift-XRT team.

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