Skip to main content
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 16550

GRB 140709A: Swift-XRT refined Analysis
2014-07-09T15:28:03Z (10 years ago)
Phil Evans at U of Leicester <>
V. D'Elia (ASDC), M. de Pasquale (INAF-IASFPA), V. Mangano (PSU), M.C.
Stroh (PSU), D.N. Burrows (PSU), P.A. Evans (U. Leicester), B.P.
Gompertz (U. Leicester), J.P. Osborne (U. Leicester), A. Maselli 
(INAF-IASFPA) and L.M.Z. Hagen report on behalf of the Swift-XRT team:

We have analysed 7.1 ks of XRT data for GRB 140709A (Hagen  et al. GCN
Circ. 16546),  from 75 s to 30.7 ks after the  BAT trigger. The data
comprise 195 s in Windowed Timing (WT) mode (the first 6 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)

The late-time light curve (from T0+5.7 ks) can be modelled with  a
power-law decay with a decay index of alpha=0.89 (+0.08, -0.09).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 2.48 (+/-0.07). The
best-fitting absorption column is  9.9 (+/-0.5) x 10^21 cm^-2, in
excess of the Galactic value of 4.1 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.88 (+/-0.14) and a
best-fitting absorption column of 8.0 (+1.2, -1.1) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 4.9 x 10^-11 (8.0 x 10^-11) erg cm^-2

A summary of the PC-mode spectrum is thus:
Total column:	     8.0 (+1.2, -1.1) x 10^21 cm^-2
Galactic foreground: 4.1 x 10^21 cm^-2
Excess significance: 5.8 sigma
Photon index:	     1.88 (+/-0.14)

If the light curve continues to decay with a power-law decay index of
0.89, the count rate at T+24 hours will be 0.038 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.9 x
10^-12 (3.1 x 10^-12) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at

This circular is an official product of the Swift-XRT team.
Looking for U.S. government information and services? Visit