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GCN Circular 33681

GRB 230423A: Swift-XRT refined Analysis
2023-04-25T04:27:05Z (a year ago)
Phil Evans at U of Leicester <>
J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), D.N. Burrows (PSU), P.A.
Evans (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester), M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR), V.
D'Elia (SSDC & INAF-OAR) and  report on behalf of the Swift-XRT team:

We have analysed 2.5 ks of XRT data for GRB 230423A, from 680 s to 57.3
ks after the  BAT trigger. The data comprise 22 s in Windowed Timing
(WT) mode with the remainder in Photon Counting (PC) mode. The refined
XRT position is RA, Dec = 122.5830, -21.9259 which is equivalent to:

RA (J2000): 08 10 19.91
Dec(J2000): -21 55 33.1

with an uncertainty of 3.7 arcsec (radius, 90% confidence).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.19 (+0.39, -0.28).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.6 (+/-0.8). The
best-fitting absorption column is  3.3 (+1.5, -1.3) x 10^22 cm^-2, in
excess of the Galactic value of 2.0 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 5.9 x 10^-11 (2.8 x 10^-10) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     3.3 (+1.5, -1.3) x 10^22 cm^-2
Galactic foreground: 2.0 x 10^21 cm^-2
Excess significance: 4.1 sigma
Photon index:	     2.6 (+/-0.8)

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

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

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