GCN Circular 8561
Subject
GRB 081126: Swift-XRT refined analysis
Date
2008-11-27T12:04:20Z (15 years ago)
From
Raffaella Margutti at U. di Milano Bicocca <raffaella.margutti@brera.inaf.it>
R. Margutti (Univ. Bicocca & INAF-OAB) reports on behalf of the Swift
XRT team:
We have analysed the first 5 orbits of Swift-XRT data obtained for GRB
081126
(Margutti et al., GCN Circ. 8554), covering 100 s of Windowed Timing
(WT) and 9.1 ks of Photon Counting (PC) mode data, respectively, between 77
and 24 ks after the trigger.
The UVOT-enhanced XRT position was given by Osborne et al. in GCN Circ.
8556.
The light-curve can be modelled by a double broken power-law,
with an initial decay of alpha_1= 1.2 +/- 0.2, a flat decay
of alpha_2= 0.6 +/- 0.1 and a final value of alpha_3= 2.1 +/- 0.2.
The two break times are around 200 and 9000 s, respectively.
A spectrum extracted from WT data can be modelled with an
absorbed power-law, with Gamma = 1.9 +/- 0.2 .
A spectrum extracted from PC data in the time interval 3-30 ks post
trigger
can be modelled with an absorbed power-law, with Gamma = 2.0 +/- 0.1 and
a column density of NH = (5.0 +/- 0.7)x10^21 cm^-2, which is compatible with
the Galactic value in this direction (4.1x10^21 cm^-2).
The observed (unabsorbed) 0.3 -10 keV flux over this time
interval is 7.1x10^-12 (1.2x10^-11) erg cm^-2 s^-1.
For both spectra there is no strong evidence for intrinsic NH.
Uncertainties are given at 90% confidence.
If the light-curve continues to decay with alpha ~ 2, the count rate 24
hours after the burst is estimated to be 2.7x10^-3 count s^-1, which
corresponds to an observed flux of 1.4x10^-13 erg cm^-2 s^-1.
The results of the xrt automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00335647.
This is an official product of the Swift-XRT team.