[vsnet-grb-info 3013] GRB 060306: Swift-XRT team refined analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4850
SUBJECT: GRB 060306: Swift-XRT team refined analysis 
DATE:    06/03/06 12:30:14 GMT
FROM:    Kim Page at U.of Leicester  <kpa at star.le.ac.uk>

K.L. Page, M.R. Goad (U. Leicester) and L. Angelini (GSFC) report on 
behalf of the Swift-XRT team:

The XRT began observing the field of GRB 060306 88 seconds after the BAT 
trigger. Analysing the first 5 orbits of data, the following refined 
position was obtained:

RA(J2000) =  02h 44m 23.0s
Dec(J2000)= -02d 08' 52.8"

with an estimated uncertainty of 3.9 arcsec (90% containment). This is 4.7 
arcsec from the XRT position given in GCN 4848 (Angelini et al.), and 
21.3 arcsec from the BAT position reported in the same circular.

The light-curve shows a steep initial decay, with alpha ~3.4, breaking to 
a slope of ~0.6 at ~210 seconds after the trigger time. 

The WT spectrum (96-173 seconds after the trigger) can be fitted with a
power-law of Gamma = 2.1 +/- 0.3, with NH ~4 x 10^21 cm^-2 (in addition to
the estimated Galactic value of 3.6 x 10^20 cm^-2). There is no evidence
for spectral evolution across the break in the light-curve. The observed
(unabsorbed) flux over 0.3-10 keV for the WT spectrum is 2.24 x 10^-10
(3.90 x 10^-10) erg cm^-2 s^-1.

Assuming the current decay of alpha ~0.6 continues, the estimated count 
rate at 24 hours is 0.02 ct s^-1, corresponding to an observed 
(unabsorbed) flux of 1.3 x 10^-12 (2.9 x 10^-12) erg cm^-2 s^-1.

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