GCN Circular 3209

G. Chincharini, P. Romano, S. Campana, C. Pagani, G. Tagliaferri
(INAF-OAB), M. Capalbi, P. Giommi (ASDC), J. Kennea, D. N. Burrows (PSU),
A. Wells, O. Godet (U. Leicester), G. Cusumano, V. Mangano (IASF/Palermo),
L. Cominsky (Sonoma State U.), K. Hurley (UCB), and N. Gehrels (GSFC),
report on behalf of the Swift XRT team:

We have analyzed the Swift XRT data from GRB 050408 (Sakamoto et al. 2005, 
GCN 3189
Not found
 
 
; Wells et al. 2005, GCN 3191
Not found
 
 
) using 8 orbits with a total exposure 
time of 6417 s in Photon Counting (PC) mode. The refined coordinates of the 
X-ray afterglow are:

RA(J2000) = 12:02:17.5
Dec(J2000) = +10:51:06.5

We estimate an uncertainty of 5 arcseconds radius (90% containment).  This 
position is 3.9 arcsec from the optical candidates (De Ugarte-Postigo et 
al., GCN 3192
Not found
 
 
; Chen et al., GCN 3199
Not found
 
 
).

The [0.2-10] keV light curve in PC mode starts 2555 seconds after the 
HETE-II trigger (T0).  The count rate is decaying following a power law 
with a slope of about 0.8 over a time interval of 40 ks. With the current 
data we do not see evidence of a break in the XRT light curve.

A preliminary spectral fit to the PC data gives a power law photon index of 
2.2 +/- 0.2 in the [0.5-10] keV band, with a column density of 
(2.5+/-0.6)E21 cm^-2 (the Galactic value is 1.8E20 cm^-2).  The average 
unabsorbed 0.5-10 keV flux is about 6.2E-12 erg
cm^-2 s^-1 (in the time range 2.5-43.5 ks from trigger).