GCN Circular 42665

S. Lanava (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne (U.
Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A.
Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB) and
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:

We have analysed 847 s of XRT data for GRB 251112A, from 90 s to 939 s
after the  Swift trigger. The data comprise 64 s in Windowed Timing
(WT) mode with the remainder in Photon Counting (PC) mode. The refined
XRT position is RA, Dec = 274.0697, +24.1535 which is equivalent to:

RA (J2000): 18h 16m 16.72s
Dec(J2000): +24d 09' 12.5"

with an uncertainty of 4.1 arcsec (radius, 90% confidence).

The light curve can be modelled with a power-law decay with a decay
index of alpha=3.14 (+0.34, -0.30).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 3.3 (+/-0.4). The
best-fitting absorption column is  4.9 (+1.3, -1.1) x 10^21 cm^-2, in
excess of the Galactic value of 1.8 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 2.2 x 10^-11 (1.1 x 10^-10) erg
cm^-2 count^-1. 

A summary of the WT-mode spectrum is thus:
Total column:	     4.9 (+1.3, -1.1) x 10^21 cm^-2
Galactic foreground: 1.8 x 10^21 cm^-2
Excess significance: 4.6 sigma
Photon index:	     3.3 (+/-0.4)

If the light curve continues to decay with a power-law decay index of
3.14, the count rate at T+24 hours will be 7.8 x 10^-9 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.7 x
10^-19 (8.4 x 10^-19) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
https://www.swift.ac.uk/xrt_products/01413695.

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