[vsnet-grb-info 3829] GRB060929: Swift-XRT refined analysis.

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  5663
SUBJECT: GRB060929: Swift-XRT refined analysis.
DATE:    06/09/30 03:40:42 GMT
FROM:    Andy Beardmore at U Leicester  <apb at star.le.ac.uk>

A. P. Beardmore (U. Leicester), D. N. Burrows (PSU), K. L. Page 
(U. Leicester) and C. B. Markwardt (GSFC/UMD) report on behalf of 
the Swift-XRT team:

We have analysed the first  orbit of Swift-XRT data of GRB 060929
(Markwardt et al., GCN 5654).

>From 1.9ks of Photon Counting mode data, we derive a refined XRT
position of:

RA(J2000)  =  17h 32m 29.0s
Dec(J2000) = +29d 50' 08.9"

with an error radius of 5.5 arcsec (90% confidence, including boresight
uncertainties). This is within 0.4 arcsec of the initial XRT position,
and 2.0 arcmin of the refined BAT position (Fenimore et al., GCN 5660).

The XRT light curve from the first orbit shows a giant flare from
T+410s to T+1180s, which peaks at a count rate of ~70 count s^-1 at
T+535s (where T is the trigger time). This flare is also seen in BAT
data (Palmer et al., GCN 5662).

The average Windowed Timing mode spectrum during the flare (from
T+476s to T+691s; count rate equal to 36.7 count s^-1) can be
described by a absorbed power-law, with a column density of
1.85+/-0.15 e21 cm^-2 and a photon index of 1.86+/-0.05. The 0.3-10.0
keV observed (unabsorbed) flux during this interval is 1.61E-09
(2.15E-09) ergs cm^-2 s^-1.

The underlying non-flare emission is weak (0.07 count s^-1), and can
be fit with a power-law of photon index 2.3+1.4-0.8 and an
unconstrained column density less than 3.6e21 cm^-2. The 0.3-10.0 keV
observed (unabsorbed) flux is 3.3E-12 (5.3E-12) ergs cm^-2 s^-1
The Galactic column in the direction of the source is 3.6e20 cm^-2.

We have insufficient data at this time to predict a later
time X-ray decay slope and  flux.

This circular is an official product of the Swift-XRT Team.