TITLE:   GCN CIRCULAR
NUMBER:  40423
SUBJECT: GRB 250510A: Swift-XRT observations
DATE:    25/05/10 16:54:51 GMT
FROM:    Simone Dichiara at Pennsylvania State University <sbd5667@psu.edu>

S. Dichiara (PSU), K.L. Page (U. Leicester), J.A. Kennea (PSU), 
P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E. Ambrosi  
(INAF-IASFPA) , M. A. Williams (PSU), J.P. Osborne (U. Leicester), 
A.P. Beardmore (U. Leicester) 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 250510A, from 10.2 ks to
20.8 ks after the  SVOM/ECLAIRs trigger. The data are entirely in
Photon Counting (PC) mode.  

Within the SVOM/ECLAIRs 90% C.L. error region (GCN #40415) we detect 
the EP-FXT source EPF_J185624.8+181937 (GCN#40420) at RA, Dec =
284.10364, +18.3267 which is equivalent to:

RA (J2000): 18h 56m 24.87s
Dec (J2000): +18d 19′ 36.0″

with an uncertainty of 5.7 arcsec (radius, 90% confidence).
The source has a mean count rate of 7.3e-03 ct/sec and a flux of 3.2 
(+1.3, -1.1) ×  10^-13 erg cm^-2 s^-1 (0.3-10 keV); we note that this 
position is also consistent with a known 2MASS source, 
2MASS J18562485+1819380. 

No other X-ray sources have been detected. The 3-sigma upper limit in 
the field ranges  from ~4.4e-03 to ~1.0e-02 ct s^-1, corresponding to a 
0.3-10 keV observed flux of 1.9e-13 to 4.4e-13 erg cm^-2 s^-1 (assuming 
a typical GRB spectrum).

The results of the XRT-team automatic analysis are available at
https://www.swift.ac.uk/SVOM/SVOM_FIELD00016/.

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