GCN Circular 43017

S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U.
Leicester), A.P. Beardmore (U. Leicester), C. Salvaggio (INAF-OAB), M.
Ferro (INAF-OAB), R. Brivio (INAF-OAB) and P.A. Evans report on behalf
of the Swift-XRT team:

We have analysed 6.3 ks of XRT data for GRB 251205A, from 129 s to 94.1
ks after the   trigger. The data comprise 352 s in Windowed Timing (WT)
mode (the first 9 s were taken while Swift was slewing) with the
remainder in Photon Counting (PC) mode. 

The late-time light curve (from T0+9.7 ks) can be modelled with a
power-law decay with a decay index of alpha=0.77 (+0.12, -0.11).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 2.14 (+/-0.06). The
best-fitting absorption column is  5.6 (+1.3, -1.2) x 10^20 cm^-2, in
excess of the Galactic value of 1.2 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.95 (+0.16, -0.15)
and a best-fitting absorption column of 3.8 (+3.5, -2.6) x 10^20 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.4 x 10^-11 (3.7 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     3.8 (+3.5, -2.6) x 10^20 cm^-2
Galactic foreground: 1.2 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.95 (+0.16, -0.15)

The results of the XRT-team automatic analysis are available at
https://www.swift.ac.uk/xrt_products/01420873.

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