GCN Circular 16197

M.C. Stroh (PSU), D.N. Burrows (PSU), K.L. Page (U. Leicester), C.
Pagani (U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri
(INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), P. D'Avanzo (INAF-OAB), J.A.
Kennea (PSU) and M.H. Siegel report on behalf of the Swift-XRT team:

We have analysed 7.0 ks of XRT data for GRB 140430A (Siegel  et al. GCN
Circ. 16190
Not found
 
 
),  from 132 s to 23.5 ks after the	BAT trigger. The data
comprise 382 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Evans et al. (GCN Circ. 16195
Not found
 
 
).

The late-time light curve (from T0+3.8 ks) can be modelled with  a
power-law decay with a decay index of alpha=0.68 (+0.12, -0.13).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 2.05 (+/-0.04). The
best-fitting absorption column is  3.7 (+1.4, -1.3) x 10^21 cm^-2, at a
redshift of 1.6, in addition to the Galactic value of 2.1 x 10^21 cm^-2
(Willingale et al. 2013). The PC mode spectrum has a photon index of
2.21 (+0.20, -0.19) and a best-fitting absorption column of 5.3 (+6.5,
-5.3) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV
flux conversion factor deduced from this spectrum  is 3.3 x 10^-11 (5.2
x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Galactic foreground: 2.1 x 10^21 cm^-2
Intrinsic column:    5.3 (+6.5, -5.3) x 10^21 cm^-2 at z=1.6
Photon index:	     2.21 (+0.20, -0.19)

If the light curve continues to decay with a power-law decay index of
0.68, the count rate at T+24 hours will be 0.018 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.0 x
10^-13 (9.6 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/00597722.

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