TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4066
SUBJECT: GRB 051006: XRT refined analysis
DATE:    05/10/07 18:04:32 GMT
FROM:    Milvia Capalbi at ISAC/ASDC  <capalbi@asdc.asi.it>

M. Capalbi, M. Perri (ASDC), J. Kennea, D.N. Burrows, D. Morris (PSU), 
L. Angelini (GSFC-JHU), J. Greiner (MPE) report on behalf of the Swift 
XRT team:

We have analyzed the first six orbits of the Swift XRT data for GRB 
051006 ((trigger #158593, Norris et al., GCN 4061). The refined 
coordinates of the X-ray afterglow are:

RA(J2000) = 07 23 13.7
Dec(J2000) = +09 30 20.3

with an estimated uncertainty of 8 arcseconds radius (90% containment).
This position is 16 arcseconds from the BAT refined position (Palmer et
al., GCN 4063), 3.7 arcseconds from the early XRT position (Morris et 
al., GCN 4062) and 3.7 arcseconds from the optical source reported by de 
Ugarte et al. (GCN 4064).

Data in  Windowed Timing (WT) mode starts at 20:32:26 UT, 113 seconds
after the BAT trigger, then the XRT switched to Photon Counting mode.

The light curve shows a flaring behaviour in the first orbit,and has a 
decay index of -1.7 +/- 0.05 obtained excluding the flare time interval.

A preliminary spectral fit (simple absorbed power-law) to the WT data
yields a photon index of 1.6 +/- 0.4 in the 0.7-10 keV band.
The derived NH is (7 +/- 3)E21 cm^-2, which is higher than the Galactic
value  (8.6E+20 cm-2; Dickey & Lockman 1990).