TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3889
SUBJECT: GRB 050826: Swift XRT preliminary analysis results
DATE:    05/08/26 21:31:23 GMT
FROM:    Milvia Capalbi at ISAC/ASDC  <capalbi@asdc.asi.it>

V. Mangano (INAF-IASF), D. Morris  (PSU), D. Burrows (PSU),
J. Kennea (PSU), L. Angelini (GSFC-JHU), N. White (GSFC)
report on behalf of the Swift XRT team:

We have analyzed the Swift XRT data from the first
observation  of GRB 050826 (four orbits).
The new refined coordinates are:

RA(J2000) = 05h 51m 01.3s  Dec(J2000) = -02:38:41.9

with an uncertainty of 6 arcseconds radius (90% containment).
This position is 2.6 arcmin from the BAT position given
in GCN 3384 (Mangano et al 2005a) and consistent with
the previously distributed coodinates given in GCN 3385
(Mangano et al 2005b).

The 0.2-10 keV light curve in Photon Counting (PC) mode
starts 114.97 seconds from the BAT trigger.
The light curve shows a single power law decay with slope
-1.16 +/- 0.07 (90% confidence level).

A preliminary spectral fit to the first orbit PC data
gives a spectral power law photon index of 2.0 +/- 0.4
in the [0.2-10] keV band, with an absorption column
of 8e21 cm^2, in excess of the Galactic value (2e21 cm^2).

The average (in the time range 100-700 seconds from trigger)
estimated unabsorbed 0.5-10 keV flux is then
6.9E-11 erg cm-2 s-1.

The predicted flux at T=24 h after the trigger is
at the level of 7.0e-14 erg cm-2 s-1 (or 1.0e-3 counts/s).