GCN Circular 5681
Subject
GRB 061002: Swift-XRT Team Refined Analysis
Date
2006-10-02T08:02:37Z (18 years ago)
From
Kim Page at U.of Leicester <kpa@star.le.ac.uk>
K.L. Page (U. Leicester) and J.K. Cannizzo (NASA/UMBC) report on behalf of
the Swift-XRT team:
We have analysed the first 3 orbits of GRB 061002 data obtained by the
Swift-XRT. Using the 4.5 ks of Photon Counting data from the second and
third orbits (the first orbit of data was entirely in Windowed Timing
mode), we find a refined position of:
RA(J2000) = 14 41 23.29
Dec(J2000) = +48 44 30.5
with an estimated uncertainty of 7.5 arcsec (90% confidence, including
boresight uncertainties). This lies 7.8 arcsec from the initial XRT
position given by Cannizzo et al. in GCN Circ. 5675, and 60.7 arcsec from
the ground-calculated BAT position (GCN Circ. 5678; Hullinger et al.)
The X-ray light-curve shows a break from a steep decay slope of alpha_1 =
2.97 +/- 0.31 to alpha_2 = 1.25 +/- 0.12 at about 304 seconds after the
trigger.
The Windowed Timing spectrum can be modelled by a power-law with a column
density in excess of the Galactic value in that direction. The fit
parameters are: Gamma = 2.19 +0.36/-0.31 and NH_excess = (1.5
+0.8/-0.7)e21 cm^-2 (in addition to NH_Galactic = 2.07e20 cm^-2). The mean
observed (unabsorbed) flux over this first orbit (138-1345s after the
burst) was found to be 1.24e-11 (1.90e-11) erg cm^-2 s^-1.
If the decay continues at a rate of alpha = 1.25, the estimated count rate
at 24 hours will be 4.1e-4 count s^-1, corresponding to an observed
(unabsorbed) flux of 1.86e-14 (2.79e-14) erg cm^-2 s^-1.
This circular is an official product of the Swift-XRT team.