TITLE:   GCN CIRCULAR
NUMBER:  41831
SUBJECT: GRB 250912A: Swift-XRT observations
DATE:    25/09/14 14:45:17 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 250912A (Ducoin et al., GCN 41820; Wang et al., GCN 41826; see also Fermi GBM
team, GCN 41819), collecting 2.2 ks of Photon Counting (PC) mode data between T0+11
ks and T0+55 ks after the trigger. We have detected 1 source.  This has been
automatically classified as an uncatalogued X-ray source.

Uncatalogued X-ray sources
--------------------------

  Source 1 (SWIFT J010009.7+111047):
  ==================================
    RA (J2000.0):   15.0405  =	01 00 09.72
    Dec (J2000.0):  +11.1797  =  +11 10 46.9
    Error:	    7.3 (arcsec, radius, 90% confidence).
    Detect flag:    GOOD
    Distance:	    6.8 arcmin from the SVOM/ECLAIRs position.
    Mean rate:	    (3.6 [+2.0, -1.5])e-3 ct s^-1
    Mean flux:	    (2.7 [+1.5, -1.1])e-13 erg cm^-2 s^-1
    Peak rate:	    (3.6 [+2.0, -1.5])e-3 ct s^-1
    Peak flux:	    (2.7 [+1.5, -1.1])e-13 erg cm^-2 s^-1
    ECF:	    7.43e-11 erg cm^-2 ct^-1
		      assuming NH=5.11e+20 cm^-2, gamma=0.69
		      determined from a spectral fit.
    RASS UL:	    7.3e-02 ct s^-1 (converted to XRT; 0.3-10 keV)
		      so the source is not above this 3-sigma upper limit.
    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.

We note that source 1 lies outside the MXT error region reported by Ducoin et al.
(GCN 41820), so it is likely unrelated with the GRB.

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_FIELD00037.

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