GCN Circular 5695
Subject
GRB 061004: Swift-XRT Team Refined Analysis
Event
Date
2006-10-05T01:32:12Z (19 years ago)
From
Kim Page at U.of Leicester <kpa@star.le.ac.uk>
K.L. Page, A.P. Beardmore (U. Leicester) & H. Ziaeepour (UCL-MSSL) report
on behalf of the Swift-XRT Team:
We have analysed the first 2 orbits of Swift-XRT data obtained for GRB
061004 (GCN Circ. 5691; Ziaeepour et al.). Using 3.8 ks of Photon Counting
mode data, we derive a refined position of:
RA(J2000) = 06 31 10.48
Dec(J2000) = -45 54 24.6
with an estimated error radius of 5.5 arcsec (90% confidence, including
boresight uncertainties). This lies 0.7 arcsec from the original XRT
position given in GCN Circ. 5691 and 14.2 arcsec from the
ground-calculated BAT position in GCN Circ. 5694 (Krimm et al).
The X-ray light-curve shows an initial decay of alpha = 1.62 +/- 0.14,
breaking around 375 seconds after the burst to a flatter decay slope of
0.61 +/- 0.10.
The WT spectrum can be modelled using a power-law of Gamma = 1.53 +/-
0.48, absorbed by the Galactic column of 5.7e20 cm^-2. There is no
evidence for any excess NH. The mean observed (unabsorbed) flux over
0.3-10 keV for this spectrum (spanning a time of 68-86 seconds after the
trigger) is 2.83e-10 (3.07e-10) erg cm^-2 s^-1.
If the decay continues with a slope of alpha ~ 0.61, the count rate at 24
hours after the burst is predicted to be 0.012 count s^-1. Using a
conversion factor of 1 count s^-1 being approximately equivalent to
4.6e-11 erg cm^-2 s^-1 (observed flux), this corresponds to a flux of
2.8e-11 erg cm^-2 s^-1 (over 0.3-10 keV). The predicted unabsorbed flux at
24 hours is 3.2e-11 erg cm^-2 s^-1.
This circular is an official product of the Swift-XRT team.