TITLE:   GCN CIRCULAR
NUMBER:  8738
SUBJECT: GRB 081226: Swift-XRT refined analysis
DATE:    08/12/26 22:40:57 GMT
FROM:    Olivier Godet at U.of Leicester  <og19@star.le.ac.uk>

O. Godet (U Leicester) on behalf the Swift-XRT team:
 
The Swift-XRT started observing the field of GRB 081226 (trigger number
338177, Godet et al., GCN Circ. 8729) at 2008-12-26 01:05:11.9 UT, 94.5
seconds after the trigger. Using 11.6 ks of photon counting (PC) mode data,
the best XRT position is located at RA, Dec 120.50152, -69.02924 which is
equivalent to:
RA(J2000) = 08h 02m 00.36s
Dec(J2000) = -46d 01' 45.2"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 2.8 arcseconds from the XRT position given in Godet et al. (GCN
Circ. 8729). It is also consistent with the position of the possible 
optical counterpart reported by Afonso et al. (GCN Circ. 8731).
 
The X-ray light curve presently spans 11.6 ks of PC mode data from T+109 s 
to T+42 ks. Due to poor statistics, it is difficult to properly model the
light-curve, which shows a decay (with a slope around 1.8) possibly followed 
by a flattening at later time.
 
The PC X-ray spectrum from the same interval can be well fit by an absorbed
power-law with a photon index of 2.60 +1.61/-0.98 and a column density of 
(6.4 +8.8/-4.6) x 10^21 cm^-2 (the Galactic value is 1.19 x 10^21 cm^-2 in 
the direction of the burst - Kalberla et al. 2005).  The observed 0.4-10.0 
keV flux is (1.8 +0.8/-1.3) x 10^-13 erg cm^-2 s^-1 which corresponds to 
an unabsorbed flux of (4.7 +1.4/-2.5) x 10^-13 erg cm^-2 s^-1.
 
No more Swift observations are planned for this burst.
 
This is an official product of the Swift-XRT team.