GCN Circular 3209
Subject
GRB 050408: Swift XRT analysis
Event
Date
2005-04-09T17:07:34Z (21 years ago)
From
David Burrows at PSU/Swift <dxb15@psu.edu>
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; Wells et al. 2005, GCN 3191) 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; Chen et al., GCN 3199).
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).