TITLE:   GCN CIRCULAR
NUMBER:  40928
SUBJECT: GRB 250702F: Swift-XRT refined Analysis
DATE:    25/07/04 00:28:33 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.ac.uk>

J.P. Osborne (U. Leicester), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti
(INAF-OAB), C. Salvaggio (INAF-OAB), D.N. Burrows (PSU), M.A. Williams
(PSU), S. Dichiara (PSU), K.L. Page (U. Leicester) and P.A. Evans
report on behalf of the Swift-XRT team:

We have analysed 5.2 ks of XRT data for GRB 250702F, from 94 s to 94.1
ks after the   trigger. The data comprise 420 s in Windowed Timing (WT)
mode with the remainder in Photon Counting (PC) mode. 

The late-time light curve (from T0+3.9 ks) can be modelled with a
power-law decay with a decay index of alpha=1.01 (+/-0.06).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 2.016 (+/-0.029). The
best-fitting absorption column is  3.5 (+/-0.5) x 10^21 cm^-2, at a
redshift of 1.52, in addition to the Galactic value of 1.3 x 10^20
cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index
of 1.95 (+/-0.13) and a best-fitting absorption column of 2.1 (+2.1,
-1.9) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV
flux conversion factor deduced from this spectrum  is 3.3 x 10^-11 (3.7
x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Galactic foreground: 1.3 x 10^20 cm^-2
Intrinsic column:    2.1 (+2.1, -1.9) x 10^21 cm^-2 at z=1.52
Photon index:	     1.95 (+/-0.13)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01329888.

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