GCN Circular 4850

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
Not found
 
 
 (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.