GCN Circular 33744

A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), J.P. Osborne
(U. Leicester), B. Sbarufatti (INAF-OAB), A. D'Ai (INAF-IASFPA), A.
Melandri (INAF-OAR), J. D. Gropp (PSU), S. Dichiara (PSU), J.A. Kennea
(PSU) report on behalf of the Swift-XRT team:

We have analysed 6.2 ks of XRT data for GRB 230506C, from 4.6 ks to
97.1 ks after the  BAT trigger. The data are entirely in Photon
Counting (PC) mode. Using 1929 s of PC mode data and 5 UVOT images, we
find an enhanced XRT position (using the XRT-UVOT alignment and
matching UVOT field sources to the USNO-B1 catalogue): RA, Dec =
134.36764, +45.13295 which is equivalent to:

RA (J2000): 08h 57m 28.23s
Dec(J2000): +45d 07' 58.6"

with an uncertainty of 2.1 arcsec (radius, 90% confidence).

The light curve can be modelled with a power-law decay with a decay
index of alpha=0.81 (+0.11, -0.10).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.09 (+0.25, -0.23). The
best-fitting absorption column is  9.1 (+6.2, -5.3) x 10^20 cm^-2, in
excess of the Galactic value of 2.2 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 3.1 x 10^-11 (3.9 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     9.1 (+6.2, -5.3) x 10^20 cm^-2
Galactic foreground: 2.2 x 10^20 cm^-2
Excess significance: 2.2 sigma
Photon index:	     2.09 (+0.25, -0.23)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01167288.

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