GCN Circular 9496
Subject
GRB 090607: XRT Team Refined Analysis
Date
2009-06-07T18:39:42Z (16 years ago)
From
Kim Page at U.of Leicester <kpa@star.le.ac.uk>
K.L. Page, A.P. Beardmore, P.A. Evans (U. Leicester) & F.E. Marshall
(NASA/GSFC) report on behalf of the Swift-XRT team:
We have analysed the four orbits of XRT data obtained for GRB 090607
(Marshall et al., GCN Circ. 9491), comprising 108 s of Windowed Timing
(WT) mode and 9.5 ks of Photon Counting (PC) mode. The refined XRT
position is RA, Dec = 191.16914, 44.10503, which is equivalent to
RA (J2000) = 12 44 40.59
Dec(J2000) = +44 06 18.10
with an uncertainty of 3.7 arcsec (radius, 90% containment).
The X-ray light-curve initially brightens slightly, with a power-law of
alpha = -0.8 +/- 0.5 until 150 +10/-8 s, at which point the afterglow
starts to decay with alpha = 5.6 +0.5/-0.3. Between ~200 and 400 s after
the trigger there is a deviation from the decay in the form of a flare.
The afterglow is no longer detected after the end of the first orbit of
data (~2365 s after the trigger).
The WT data show a softening trend with time. A spectrum formed from the
PC mode data from the first orbit can be fitted with a power-law of photon
index Gamma = 1.88 +/- 0.21, absorbed by the Galactic column of 1.8x10^20
cm^-2. The observed (unabsorbed) 0.3-10 keV flux over this time is
5.5x10^-12 (5.8x10^-12) erg cm^-2 s^-1, which corresponds to a counts to
observed (unabsorbed) flux conversion factor of 3.9x10^-11 (4.1x10^-11)
erg cm^-2 count^-1.
Because of the lack of detection after the first orbit of data, we cannot
sensibly predict the future count rate.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00354299.
This circular is an official product of the Swift-XRT team.