Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 30520

GRB 210725B: Swift-XRT refined Analysis
2021-07-26T18:58:04Z (3 years ago)
Phil Evans at U of Leicester <>
V. D'Elia (SSDC & INAF-OAR), A. D'Ai (INAF-IASFPA), D.N. Burrows (PSU),
J. D. Gropp (PSU), J.A. Kennea (PSU), K.L. Page (U. Leicester), A.P.
Beardmore (U. Leicester), P.A. Evans (U. Leicester), A. Melandri
(INAF-OAB) and M.G. Bernardini report on behalf of the Swift-XRT team:

We have analysed 4.9 ks of XRT data for GRB 210725B (Bernardini et al.
GCN Circ. 30508), from 94 s to 107.1 ks after the  BAT trigger. The
data comprise 68 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Goad et al. (GCN Circ. 30510).

The light curve can be modelled with a power-law decay with a decay
index of alpha=3.43 (+0.20, -0.18).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.77 (+0.29, -0.27). The
best-fitting absorption column is  6.6 (+2.7, -2.1) x 10^21 cm^-2, in
excess of the Galactic value of 2.0 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 4.5 x 10^-11 (6.7 x 10^-11) erg
cm^-2 count^-1. 

A summary of the WT-mode spectrum is thus:
Total column:	     6.6 (+2.7, -2.1) x 10^21 cm^-2
Galactic foreground: 2.0 x 10^20 cm^-2
Excess significance: 5.2 sigma
Photon index:	     1.77 (+0.29, -0.27)

The results of the XRT-team automatic analysis are available at

This circular is an official product of the Swift-XRT team.
Looking for U.S. government information and services? Visit