[vsnet-grb-info 15270] GRB 140709B: Swift-XRT refined Analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16562
SUBJECT: GRB 140709B: Swift-XRT refined Analysis
DATE:    14/07/10 04:29:04 GMT
FROM:    Phil Evans at U of Leicester  <pae9 at leicester.ac.uk>

M. de Pasquale (INAF-IASFPA), M.C. Stroh (PSU), D.N. Burrows (PSU),
J.A. Kennea (PSU), B.P. Gompertz (U. Leicester), J.P. Osborne (U.
Leicester), K.L. Page (U. Leicester), A. Maselli  (INAF-IASFPA), A.
Melandri (INAF-OAB) and C.A. Swenson report on behalf of the Swift-XRT
team:

We have analysed 10.0 ks of XRT data for GRB 140709B (Swenson  et al.
GCN Circ. 16551),  from 85 s to 28.9 ks after the  BAT trigger. The
data comprise 207 s in Windowed Timing (WT) mode (the first 4 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 Goad
et al. (GCN Circ. 16556).

The late-time light curve (from T0+4.8 ks) can be modelled with  a
power-law decay with a decay index of alpha=0.99 (+0.13, -0.12).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.14 (+/-0.07). The
best-fitting absorption column is  2.2 (+0.5, -0.4) x 10^21 cm^-2, in
excess of the Galactic value of 4.3 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.05 (+0.14, -0.13)
and a best-fitting absorption column of 1.9 (+/-0.4) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.4 x 10^-11 (4.7 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.9 (+/-0.4) x 10^21 cm^-2
Galactic foreground: 4.3 x 10^20 cm^-2
Excess significance: 5.7 sigma
Photon index:	     2.05 (+0.14, -0.13)

If the light curve continues to decay with a power-law decay index of
0.99, the count rate at T+24 hours will be 0.010 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.5 x
10^-13 (4.9 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/00603866.

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