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 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.