TITLE:   GCN CIRCULAR
NUMBER:  34470
SUBJECT: GRB 230816A: Swift-XRT refined Analysis
DATE:    23/08/17 21:21:12 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.ac.uk>

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

We have analysed 3.9 ks of XRT data for GRB 230816A, from 97 s to 91.3
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=1.44 (+0.27, -0.43).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.66 (+0.31, -0.14). The
best-fitting absorption column is  consistent with the Galactic value
of 2.9 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 4.4 x 10^-11 (5.6 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     2.9 (+/-1.2) x 10^21 cm^-2
Galactic foreground: 2.9 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.66 (+0.31, -0.14)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01185673.

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