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.