[vsnet-grb-info 3570] GRB 060805: XRT Team Refined Analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  5404
SUBJECT: GRB 060805: XRT Team Refined Analysis 
DATE:    06/08/05 16:59:13 GMT
FROM:    Kim Page at U.of Leicester  <kpa at star.le.ac.uk>

K.L. Page, O. Godet (U Leicester) & H.Z. Ziaeepour (UCL-MSSL) report on
behalf of the Swift-XRT team:

We have analysed the first 4 orbits of the XRT data obtained for GRB
060805 (trigger 222683), comprising 8.4 ks of Photon Counting mode data
between 101 s - 18.3 ks after the BAT trigger. Using these data, we obtain
a refined position of:

RA(J2000)  =  14 43 43.59
Dec(J2000) = +12 35 13.2

with an uncertainty of 3.9 arcsec (90% containment). This is 47.9 and 1.4
arcsec from the initial BAT and XRT positions respectively (GCN Circ 5398;
Ziaeepour et al).

The X-ray afterglow is faint, with a count rate of ~0.1 count s^-1 at 100
seconds after the trigger. After the first orbit, during which the count
rate was close to constant, the afterglow decays with a slope of alpha =
1.06 +/- 0.35.

The spectrum (using the combined data from all 4 orbits) can be well
fitted by a simple power-law, of Gamma = 2.39 +0.64/-0.51, with a total
absorbing column of about 1e21 cm^-2 (compared to the Galactic column
density of 1.57e20 cm^-2). During the first orbit (between 101 and 935
seconds after the trigger), the 0.3-10 keV unabsorbed flux was 4.72e-12
erg cm^-2 s^-1.

If the afterglow continues to fade with alpha ~ 1.06, the count rate at 24 
hours is predicted to be 1.6e-3 count s^-1, corresponding to an observed 
(unabsorbed) flux of 5.92e-14 (8.92e-14) erg cm^-2 s^-1.

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