TITLE:   GCN CIRCULAR
NUMBER:  40389
SUBJECT: GRB 250507A: Swift-XRT refined Analysis
DATE:    25/05/07 22:02:18 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.ac.uk>

J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore
(U. Leicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E.
Ambrosi  (INAF-IASFPA) , M. A. Williams (PSU), S. Dichiara (PSU), J.A.
Kennea (PSU) and P.A. Evans (U. Leicester) reports on behalf of the
Swift-XRT team:

We have analysed 1.8 ks of XRT data for GRB 250507A, from 7.4 ks to
12.5 ks after the  SVOM/ECLAIRs trigger. The data are entirely in
Photon Counting (PC) mode.  We detect an uncatalogued X-ray source
within the SVOM/ECLAIRs 90% C.L. error region (GCN #40374) at RA, Dec =
183.06416, -23.5888 which is equivalent to:

RA (J2000): 12h 12m 15.40s
Dec (J2000): -23d 35' 19.6"

with an uncertainty of 4.2 arcsec (radius, 90% confidence). This
position is 15.6 arcsec from the SVOM/MXT position (GCN #40381) and 2.5
arcsec from the source detected by EP-FXT (GCN #40385).

The source has a mean count rate of 2.6e-02 ct/sec and a flux of       
1.11 (+0.21, -0.20) × 10^-12 erg cm^-2 s^-1 (0.3-10 keV); we cannot
determine at the present time whether it is fading. However, the
decrease in flux compared to the SVOM/MXT observation suggests this
source is the afterglow. 

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00019769.

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