GCN Circular 16490

J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Pagani (U.
Leicester), A. Maselli	(INAF-IASFPA), A. Melandri (INAF-OAB), B.
Sbarufatti (INAF-OAB/PSU), V. Mangano (PSU), M.C. Stroh (PSU), D.N.
Burrows (PSU) and A.Y. Lien report on behalf of the Swift-XRT team:

We have analysed 10 ks of XRT data for GRB 140629A (Lien  et al. GCN
Circ. 16477
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 ),  from 80 s to 34.9 ks after the  BAT trigger. The data
comprise 136 s in Windowed Timing (WT) mode (the first 10 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Evans et
al. (GCN Circ. 16479
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 ).

The late-time light curve (from T0+4.2 ks) can be modelled with  a
power-law decay with a decay index of alpha=1.37 (+/-0.09).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.82 (+0.17, -0.16). The
best-fitting absorption column is  4.5 (+3.8, -3.4) x 10^20 cm^-2, in
excess of the Galactic value of 9.3 x 10^19 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.98 (+/-0.10) and a
best-fitting absorption column of 5.2 (+2.2, -2.0) x 10^20 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.3 x 10^-11 (3.7 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     5.2 (+2.2, -2.0) x 10^20 cm^-2
Galactic foreground: 9.3 x 10^19 cm^-2
Excess significance: 3.5 sigma
Photon index:	     1.98 (+/-0.10)

If the light curve continues to decay with a power-law decay index of
1.37, the count rate at T+24 hours will be 7.4 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/00602884.

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