TITLE:   GCN CIRCULAR
NUMBER:  8385
SUBJECT: GRB 081011: Swift XRT refined analysis
DATE:    08/10/17 14:10:54 GMT
FROM:    Dirk Grupe at PSU/Swift-XRT  <grupe@astro.psu.edu>

Dirk Grupe (PSU)  reports on behalf of the Swift-XRT team:


The XRT began observing the field of GRB 081011 (trigger=331332; Grupe 
et al.,
GCN Circ 8355) on 2008 October 11 00:30:24.4 UT, 93.9 s after
the BAT trigger.

The enhanced XRT position given in GCN Circ 8380 (Goad et al.)
is 59.3" away from the ground-processed BAT position given in GCN Circ. 
8357
(Sakamoto et al.),  consistent with that position. This position was
outside the central 200x200 pixel XRT window which is telemetered as 
SPER data,
hence the non-detection reported in GCN 8357.


The 0.3-10 keV X-ray light curve starts at a level of 7e-11 ergs/s/cm2 (1.8
counts/s) in the XRT with a steep decay slope at these early times of
alpha1 = 1.10+/-0.23 The light curve breaks at about 4+/-2 ks after the 
burst
and flattens to alpha2 = 0.24+/-0.17. Due to the proximity to the sun
constraint, it was decided to cancel the observations after the
first day. No further observations are planned and possible due the sun
constraint.


The spectrum of the Photon Counting mode data
can be fitted by an absorbed single powerlaw with a photon
index Gamma = 2.04 +/- 0.13 and column density fixed to the Galactic 
value of
1.04e20 cm-2 in the direction of the burst. The count rate to observed flux
conversion factor is 2.2e-11 (ergs/s/cm2)/(counts/s) in the 0.3-10 keV 
band.


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