[vsnet-grb-info 3964] GRB 061102, XRT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  5783
SUBJECT: GRB 061102, XRT refined analysis
DATE:    06/11/02 13:59:45 GMT
FROM:    Rhaana Starling at GRACE/U of Amsterdam  <rlcs1 at star.le.ac.uk>

R. L. C. Starling, K. L. Page (U Leicester) and S. T. Holland (GSFC/USRA) 
report on behalf of the Swift XRT team:

We have analysed the first 3 orbits of Swift XRT data obtained for GRB 
061102 (trigger 236430, GCN 5776 Holland et al.). The data consist of 208 
s of WT mode data beginning at 112s since BAT trigger and 2560s of 
subsequent PC mode data.


Using the PC mode data we obtain a refined position of:
RA(J2000)  =  09 53 37.64
Dec(J2000) = -17 01 26.5

with an estimated uncertainty of 4.9 arcsec (90% containment) taking into 
account the new TELDEF files.
This location is 1.8 arcsec from the initial XRT position (GCN Circ. 5776) 
and 98.7 arcsec from the ground-calculated BAT position (GCN Circ. 5777;
Tueller et al.)


The lightcurve shows a steep decay over the first 400s with a slope of 
alpha = 4.0+/-0.1. At ~400s the lightcurve breaks to a slope of 
alpha~1.


The first orbit WT-mode spectrum can be well fitted with an absorbed power 
law with index Gamma = 3.6+/-0.2. The total column density required is 
1.6E21 cm^-2 which exceeds the Galactic value of 5.0E20 cm^-2 (Dickey & 
Lockman 1990). 
The total flux in the 0.3-10 keV band is 1.2E-10 erg cm^-2 s^-1.
All errors are quoted at the 90% confidence limit.
 
>From these data we predict a count rate of 3.3E-4 counts s^-1, 
corresponding to a flux of approximately 8E-15 erg cm^-2 s^-1 at T+24h.


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