GCN Circular 38945

S. Dichiara (PSU), J.A. Kennea (PSU), K.L. Page (U. Leicester), A.P.
Beardmore (U. Leicester), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti
(INAF-OAB), C. Salvaggio (INAF-OAB), D.N. Burrows (PSU) and P.A. Evans
report on behalf of the Swift-XRT team:

We have analysed 8.6 ks of XRT data for GRB 250114A, from 117 s to 28.1
ks after the  BAT trigger. The data comprise 317 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+4.6 ks) can be modelled with an
initial rise, with a power-law index of alpha=-0.94 (+1.18, -0.25),
followed by a break at T+8035 s  to an alpha of 1.32 (+0.31, -0.29).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.09 (+/-0.03). The
best-fitting absorption column is  1.8 (+/-0.9) x 10^22 cm^-2, at a
redshift of 4.732, in addition to the Galactic value of 5.1 x 10^20
cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index
of 1.87 (+0.14, -0.13) and a best-fitting absorption column of 1.0
(+2.2, -1.0) x 10^22 cm^-2. The counts to observed (unabsorbed) 0.3-10
keV flux conversion factor deduced from this spectrum  is 3.6 x 10^-11
(4.1 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Galactic foreground: 5.1 x 10^20 cm^-2
Intrinsic column:    1.0 (+2.2, -1.0) x 10^22 cm^-2 at z=4.732
Photon index:	     1.87 (+0.14, -0.13)

If the light curve continues to decay with a power-law decay index of
1.32, the count rate at T+24 hours will be 6.8 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.4 x
10^-13 (2.8 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01281241.

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