[vsnet-grb-info 28434] GRB 210726A: Swift-XRT refined Analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30537
SUBJECT: GRB 210726A: Swift-XRT refined Analysis
DATE:    21/07/27 19:57:58 GMT
FROM:    Phil Evans at U of Leicester  <pae9 at leicester.ac.uk>

A. D'Ai (INAF-IASFPA), J. D. Gropp (PSU), J.A. Kennea (PSU), A.
Tohuvavohu (U. Toronto), A.P. Beardmore (U. Leicester), P.A. Evans (U.
Leicester), J.P. Osborne (U. Leicester), A. Melandri (INAF-OAB), T.
Sbarrato (INAF-OAB) and M.G. Bernardini report on behalf of the
Swift-XRT team:

We have analysed 5.9 ks of XRT data for GRB 210726A (Bernardini et al.
GCN Circ. 30523), from 79 s to 75.9 ks after the  BAT trigger. The data
are entirely in Photon Counting (PC) mode. The enhanced XRT position
for this burst was given by Osborne et al. (GCN Circ. 30524).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.49 (+0.22, -0.26).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.2 (+/-0.3). The
best-fitting absorption column is  3.3 (+1.3, -1.2) x 10^21 cm^-2, in
excess of the Galactic value of 1.7 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 3.3 x 10^-11 (5.7 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     3.3 (+1.3, -1.2) x 10^21 cm^-2
Galactic foreground: 1.7 x 10^20 cm^-2
Excess significance: 4.5 sigma
Photon index:	     2.2 (+/-0.3)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01061687.

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