[vsnet-grb-info 3589] GRB 060807: XRT Team refined analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  5423
SUBJECT: GRB 060807: XRT Team refined analysis  
DATE:    06/08/08 09:36:25 GMT
FROM:    Kim Page at U.of Leicester  <kpa at star.le.ac.uk>

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

We have analysed the first 4 orbits of Swift-XRT data obtained for GRB 
060807 (trigger number 223217). All useful data were collected in Photon 
Counting mode, starting 117 seconds after the BAT trigger. Using these 
first 8.6 ks of data, we obtain a refined position of:

RA(J2000) =   16 50 02.97
Dec(J2000) = +31 35 30.5

with an estimated uncertainty radius of 3.5 arcsec (90% containment).

Analysis of the light-curve implies that there was a steep decay at the 
start of the observation, followed by a period of almost constant 
emission until the end of the first orbit. The data obtained for orbits 
2-4 show a decline with alpha = 1.18 +/- 0.10. 

A spectrum formed from all the PC data for the first 4 orbits (117 s - 18
ks after the trigger), can be modelled with a power-law of photon index
Gamma = 2.15 +/- 0.12, with an excess absorbing column of NH = (1.3 +/-
0.3)e21 cm^-2 in addition to the Galactic value of 2.44e20 cm^-2. The mean
0.3-10 keV observed flux for this time period is 1.02e-11 erg cm^-2 
s^-1; the unabsorbed flux is 1.50e-11 erg cm^-2 s^-1.

Assuming the light-curve continues to decay with alpha ~ 1.18, the count 
rate at 24 hours is predicted to be 0.016 count s^-1. This corresponds to 
an observed (unabsorbed) flux of 6.81e-13 (1.00e-12) erg cm^-2 s^-1.

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