GCN Circular 42119

J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore
(U. Leicester), E. Ambrosi  (INAF-IASFPA) , M. Capalbi (INAF-OAR), M.
Perri (SSDC & INAF-OAR), S. Lanava (PSU), S. Dichiara (PSU), J.A.
Kennea (PSU) and P.A. Evans report on behalf of the Swift-XRT team:

We have analysed 7.6 ks of XRT data for GRB 251005C, from 129 s to 29.0
ks after the   trigger. The data are entirely in Photon Counting (PC)
mode. 

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.34 (+/-0.06).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.41 (+0.27, -0.25). The
best-fitting absorption column is  7.1 (+2.8, -2.2) x 10^21 cm^-2, in
excess of the Galactic value of 3.2 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 6.4 x 10^-11 (8.2 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     7.1 (+2.8, -2.2) x 10^21 cm^-2
Galactic foreground: 3.2 x 10^21 cm^-2
Excess significance: 2.9 sigma
Photon index:	     1.41 (+0.27, -0.25)

If the light curve continues to decay with a power-law decay index of
1.34, the count rate at T+24 hours will be 4.2 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.7 x
10^-14 (3.5 x 10^-14) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01401726.

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