TITLE:   GCN CIRCULAR
NUMBER:  5054
SUBJECT: GRB060502: Swift-XRT refined analysis
DATE:    06/05/02 15:17:44 GMT
FROM:    Eleonora Troja at INAF-IASFPA  <nora@ifc.inaf.it>

V. La Parola, E. Troja, V. Mangano (INAF-IASFPA), S. 
Campana (INAF-OAB), K. L. Page (U Leicester), J. Kennea, 
D.N. Burrows (PSU), on behalf of the Swift-XRT team.

We have analyzed the first two orbit of data of GRB060502
(La Parola et al 2006, GCN 5047).
The XRT data set consists of 71 s exposure in Windowed
Timing (WT) mode followed by 355 s exposure in Photon
Counting (PC) mode in the first orbit and 2.4 ks in the 
second orbit.

The refined position of the source is

     RA  (2000) = 16h 03m 42.9s
     Dec (2000) = 66�� 35' 58.1"

with an uncertainty of 3.7 arcsec (90% confinement).
This position is only 1 arcsec from the one calculated 
from early downlinked data (La Parola et al 2006, GCN 5047), 
5.1 arcsec from the UVOT afterglow position and 17.6" from 
the BAT refined position (Parsons et al. GCN5053).

The 0.2-10 keV X-ray light curve shows an initial
fast decay with slope -2.87 +/- 0.11 and  a break at 252 
+/- 17 s from the trigger followed by a second decay slope
of -0.54 +/- 0.05.

The WT spectrum (collected during the pre-break phase)
can be fitted with a power law (photon index 2.3 +/-0.5)
plus a soft thermal component (which can be modelled with 
a blackbody at 0.13+/-0.02 keV), with intrinsic absorption 
(0.45+/-0.15)e22 cm-2, assuming a redshift of 1.51 
(Cucchiara et al. GCN5052).

The PC spectrum after the break is fitted with an absorbed 
power law with photon index 1.99 +/-0.15 and intrinsic absorption 
(0.6+/-0.2)e22 cm-2.
The Galactic absorption is 2.97e20 cm-2.

With the present decay slope, the 0.2-10 keV flux at 24h 
after the trigger is expected to be ~2e-12 erg/s/cm-2


This Circular is an official product of the Swift XRT 
Team.