GCN Circular 8470
Subject
GRB 081102: Swift-XRT refined analysis
Date
2008-11-03T15:16:22Z (16 years ago)
From
Boris Sbarufatti at INAF-IASF-Pa <sbarufatti@ifc.inaf.it>
V. Mangano, B. Sbarufatti, V. La Parola (INAF-IASF Pa), T. Ukwatta
(GSFC/GWU)
report on behalf of the Swift-XRT team:
Swift-XRT began observing the field of GRB 081102 (trigger 333427,
Ukwatta et
al., GCN circ.8462) at 17:46:11.5 UT, 92.0 seconds after the BAT
trigger.
We analysed data from the first 10 orbits, consisting of 151 s in
Windowed
Timing mode, from T+98 s to T+251s and 14 ks in Photon Counting mode,
from
T+251s to T+42.1 ks. The lightcurve is best fit by a broken powerlaw
model
with slopes alpha_1 = -2.35 +/- 0.15 and alpha_2= -1.22 (-0.11 +0.22)
and
break time T_break = T+560 (-160 +500)s. After the break, we observe
a strong
flare at T+960 (-11+21) s with decay time 157 +/-15 s.
The WT spectrum is best fit by a simple absorbed powerlaw with photon
index
2.7 +/- 0.1 and an absorbing column consistent with the Galactic
value of
4.9E21 cm^-2 (Kalberla et al. 2005). The observed (unabsorbed) flux
in the
0.3 - 10 keV band is 4.0E-10 (1.3E-9) erg cm^-2 s^-1. The PC spectrum
is best
fit by a simple absorbed powerlaw with photon index 1.97 +/- 0.1 and an
absorbing column consistent with the Galactic value. The observed
(unabsorbed)
flux in the 0.3 - 10 keV band is 1.1 (1.8)E-11 erg cm^-2 s^-1. The
countrate to flux
conversion factor is 7.1E-11.
The predicted countrate for November 3, 17:45 UT (T+ 24h) is 1.3E-3
counts/s
equivalent to a flux of 9.2E-14 erg cm^-2 s^-1.
All quoted errors are at 90% confidence level.
This circular is an official product of the Swift-XRT team.