Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 13592

GRB 120805A: Swift-XRT refined Analysis
2012-08-06T09:57:04Z (12 years ago)
Phil Evans at U of Leicester <>
D.N. Burrows (PSU), C. Pagani (U. Leicester), A.P. Beardmore (U.
Leicester), P.A. Evans (U. Leicester), B. Sbarufatti (INAF-OAB/PSU), G.
Stratta (ASDC), P. D'Avanzo (INAF-OAB), J.A. Kennea (PSU), M.C. Stroh
(PSU) and E. Troja report on behalf of the Swift-XRT team:

We have analysed 6.1 ks of XRT data for GRB 120805A (Troja  et al. GCN
Circ. 13588), from 126 s to 13.6 ks after the  BAT trigger. The data
comprise 115 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The refined XRT position is RA, Dec =
216.5411, +5.82554 which is equivalent to:

RA (J2000): 14 26 09.86
Dec(J2000): +05 49 31.9

with an uncertainty of 3.6 arcsec (radius, 90% confidence).

The light curve can be modelled with a series of power-law decays. The
light curve initially rises, with an index alpha=-1.497 (+0.951,
-0.003). At T+191 s it breaks to an alpha of 2.33 (+0.14, -0.12) before
breaking again at T+2805 s to a final decay with index alpha=0.3

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.43 (+0.22, -0.20). The
best-fitting absorption column is  2.1 (+0.9, -0.8) x 10^21 cm^-2, in
excess of the Galactic value of 2.2 x 10^20 cm^-2 (Kalberla et al.
2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 5.1 x 10^-11 (6.0 x 10^-11) erg
cm^-2 count^-1. 

A summary of the WT-mode spectrum is thus:
Total column:	     2.1 (+0.9, -0.8) x 10^21 cm^-2
Galactic foreground: 2.2 x 10^20 cm^-2
Excess significance: 3.7 sigma
Photon index:	     1.43 (+0.22, -0.20)

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