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 8244

GRB 080916A: Swift XRT refined analysis
2008-09-16T17:19:57Z (16 years ago)
Rhaana Starling at U of Leicester <>
R.L.C. Starling (U. Leicester) and H. Ziaeepour (MSSL-UCL) report on 
behalf of the Swift-XRT team:

We have analysed the first two orbits of Swift XRT data for GRB 080916A 
(Ziaeepour et al., GCN Circ. 8237) from T0+70 s to T0+7440 s with total 
exposure time 3.4 ks. The enhanced X-ray position is given in Evans et 
al., GCN Circ. 8241. 

The light curve can be represented by a 5-segment broken power law with an 
initial decay alpha1=1.3+0.4/-0.6 breaking at Tbk1=102+4/-6 s to a steep 
decay of alpha2=3.5+/-0.3 until Tbk2=190+25/-13 s. The light curve then 
flattens to alpha3=1.07+0.06/-0.3 and breaks at Tbk3=690+150/-140 s to a 
further steep decay of alpha4=2.9+2/-0.8. From Tbk4=1270+240/-220 s the 
decay becomes shallow again with alpha5=0.3+/-0.2. 

The spectrum from 3.2 ks of Photon Counting mode data can be fit with an 
absorbed power law with photon index Gamma=2.1+/-0.2 and intrinsic 
absorption (in excess of the Galactic value of 1.8e20 cm-2) of 
nH=(2.6+0.7/-0.6)e21 cm-2. This is consistent with the spectrum formed 
from the initial 170 s of Windowed Timing mode data. The observed 
(unabsorbed) count rate to flux conversion is 1 count/s = 4.0e-11 
(6.8e-11) erg/cm2/s. 

The predicted count rate at T+24hr would be approximately 0.1 count/s if 
the decay continues on the current plateau-like phase.

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