TITLE:   GCN CIRCULAR
NUMBER:  40987
SUBJECT: GRB 250704B: Swift-XRT refined Analysis
DATE:    25/07/06 11:00:24 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.ac.uk>

C. Salvaggio (INAF-OAB), M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), S.
Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U.
Leicester), A.P. Beardmore (U. Leicester), 
E. Ambrosi (INAF-IASF PA) and P.A. Evans (U. Leicester) reports on
behalf of the Swift-XRT team:

We have analysed 3.3 ks of XRT data for GRB 250704B, from 2.0 ks to
97.7 ks after the  Einstein Probe/WXT trigger. The data are entirely in
Photon Counting (PC) mode. Using 1717 s of PC mode data and 1 UVOT
image, we find an enhanced XRT position (using the XRT-UVOT alignment
and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec =
300.87238, +12.02301 which is equivalent to:

RA (J2000): 20h 03m 29.37s
Dec(J2000): +12d 01' 22.9"

with an uncertainty of 2.7 arcsec (radius, 90% confidence).

The light curve can be modelled with a power-law decay with a decay
index of alpha=0.9 (+0.4, -0.3).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.96 (+0.16, -0.13). The
best-fitting absorption column is  consistent with the Galactic value
of 1.5 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed
(unabsorbed) 0.3-10 keV flux conversion factor deduced from this
spectrum  is 3.6 x 10^-11 (4.3 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.47 (+/-0.25) x 10^21 cm^-2
Galactic foreground: 1.5 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.96 (+0.16, -0.13)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00019908.

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