TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3952 SUBJECT: GRB050908 : Swift-XRT refined analysis DATE: 05/09/08 17:41:45 GMT FROM: Michael Goad at U Leicester M. Goad (UL), K. Page (UL), D. Burrows (PSU) report on behalf of the Swift XRT team: We have analysed the XRT data for GRB050908 (BAT trigger 154112), between 118s and 24000 s after the trigger. As previously reported by Goad et al. (GCN3946), there is an uncatalogued fading X-ray source in the field of view. The refined coordinates for this burst are RA(J2000) : 01 21 50.38 Dec(J2000): -12 57 19.89 with an uncertainty of 6 arcseconds (90% containment). This is 43 arcseconds from the refined BAT position (GCN3951) and 6 arcseconds from the position of the candidate optical counterpart (GCN3943). The initial lightcurve displays 2 large flares with approximately equal amplitude peaking at T0+145 s and T0+397 s. The spectrum of the burst in the first orbit of data is well fit by a single powerlaw with photon index 3.9 +1.1/-0.5 (0.3-10 keV), with evidence for excess column above the Galactic value of 2.1e20 cm^-2 of NH~3e20 cm^-2. The spectrum of the burst from T0+4200 to T0+24000 s appears to be harder with a powerlaw slope of 2.0 +/-0.6. After the flares the light-curve declines with a slope of -1.33. If the light-curve continues to decline at this rate the predicted count-rate at 24 hours after the burst is 5.3e-4 ct s^-1, corresponding to a 0.3-10 keV unabsorbed flux of 3.3e-14 erg cm^-2 s^-1.