GCN Circular 9496

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
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 ), 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.