TITLE: GCN CIRCULAR NUMBER: 42232 SUBJECT: GRB 251013C: Swift-XRT counterpart detection DATE: 25/10/13 22:23:39 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 251013C (Rakotondrainibe et al., GCN 42222), collecting 1.8 ks of Photon Counting (PC) mode data between T0+344 s and T0+5.5 ks after the trigger. A bright, fading counterpart has been found, coincident with the VT optical, fading source reported by Palmerio et al. (GCN 42223), which has a redshift of 0.572 (Martin-Carrillo et al., GCN 42227). Thus, we can conclude that this is the XRT counterpart of GRB 251013C. The details of this source are:
Source 1 (SWIFT J230320.5-001235): ================================== RA (J2000.0): 345.8358 = 23 03 20.59 Dec (J2000.0): -0.2100 = -00 12 36.0 Error: 3.5 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 3.6 arcmin from the SVOM/ECLAIRs position. Mean rate: 2.356 +/- 0.081 ct s^-1 Mean flux: (8.71 +/- 0.30)e-11 erg cm^-2 s^-1 Peak rate: 10.2 +/- 1.9 ct s^-1 Peak flux: (3.76 +/- 0.69)e-10 erg cm^-2 s^-1 ECF: 3.70e-11 erg cm^-2 ct^-1 assuming NH=6.48e+20 cm^-2, gamma=1.78 determined from a spectral fit. XMM UL: 6.3e-13 erg cm^-2 s^-1, (0.3-10 keV) so the source is 5.4-sigma above this 3-sigma upper limit.
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_FIELD00041.
This circular is an official product of the Swift-XRT team.
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