TITLE:   GCN CIRCULAR
NUMBER:  34117
SUBJECT: GRB 230628E: Swift-XRT refined Analysis
DATE:    23/06/29 06:42:28 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.ac.uk>

J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), K.L. Page (U.
Leicester), A.P. Beardmore (U. Leicester), M. Capalbi (INAF-IASFPA), M.
Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), D.N. Burrows
(PSU) and P.A. Evans report on behalf of the Swift-XRT team:

We have analysed 6.3 ks of XRT data for GRB 230628E, from 226 s to 22.6
ks after the  BAT trigger. The data are entirely in Photon Counting
(PC) mode. 

The light curve can be modelled with a power-law decay with a decay
index of alpha=0.85 (+/-0.05).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.94 (+/-0.18). The
best-fitting absorption column is  9.5 (+4.9, -4.3) x 10^20 cm^-2, in
excess of the Galactic value of 4.3 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 3.4 x 10^-11 (4.1 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     9.5 (+4.9, -4.3) x 10^20 cm^-2
Galactic foreground: 4.3 x 10^20 cm^-2
Excess significance: 2.0 sigma
Photon index:	     1.94 (+/-0.18)

If the light curve continues to decay with a power-law decay index of
0.85, the count rate at T+24 hours will be 8.1 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.8 x
10^-13 (3.3 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01177054.

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