[vsnet-grb-info 1901] GRB 050802: early Swift XRT analysis results

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3740
SUBJECT: GRB 050802: early Swift XRT analysis results
DATE:    05/08/02 20:34:15 GMT
FROM:    Milvia Capalbi at ISAC/ASDC  <capalbi at asdc.asi.it>

M. Capalbi, M. Perri, P. Giommi (ASDC), J. Kennea, D.N. Burrows,
M.Chester (PSU), R. Fink (GSFC) report on behalf of the Swift XRT team:

We have analyzed the Swift XRT data from the first orbit observation of
GRB 050802 (Band et al., GCN 3734). The refined coordinates of the X-ray
afterglow are:

RA(J2000) = 14h 37m 06.1s
Dec(J2000) = +27d 47' 11"

This position is 80 arcseconds from the BAT refined position given in
GCN 3737 (Palmer et al.), 6.7 arcseconds from the early XRT position
reported in GCN 3735 (Kennea et al.) and 5.4 arcseconds from the UVOT
position (McGowan et al., GCN 3739). We estimate an uncertainty of 6
arcseconds radius in the derived position.

Data in Photon Counting (PC) mode starts at 10:15:57 UT, 475 seconds
from the BAT trigger. The 0.3-10 keV afterglow light curve shows a
fading which can be fitted with a power law of slope alpha=-0.7+/-0.1 up
to T+2875 s, when the first orbit ends.

A preliminary spectral fit in the 0.3-10.0 keV energy band to the first
orbit gives a spectral power law photon index of 1.9+/-0.1 with
nH=(6.6+/-2.5)E20 cm^-2. The Galactic nH along the line of sight is
1.8E20 cm^-2.

The unabsorbed 0.5-10.0 keV flux at 24 hours after the burst is
estimated to be 3.6E-12 erg cm^-2 s^-1.