TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3209 SUBJECT: GRB 050408: Swift XRT analysis DATE: 05/04/09 17:07:34 GMT FROM: David Burrows at PSU/Swift G. Chincharini, P. Romano, S. Campana, C. Pagani, G. Tagliaferri (INAF-OAB), M. Capalbi, P. Giommi (ASDC), J. Kennea, D. N. Burrows (PSU), A. Wells, O. Godet (U. Leicester), G. Cusumano, V. Mangano (IASF/Palermo), L. Cominsky (Sonoma State U.), K. Hurley (UCB), and N. Gehrels (GSFC), report on behalf of the Swift XRT team: We have analyzed the Swift XRT data from GRB 050408 (Sakamoto et al. 2005, GCN 3189; Wells et al. 2005, GCN 3191) using 8 orbits with a total exposure time of 6417 s in Photon Counting (PC) mode. The refined coordinates of the X-ray afterglow are: RA(J2000) = 12:02:17.5 Dec(J2000) = +10:51:06.5 We estimate an uncertainty of 5 arcseconds radius (90% containment). This position is 3.9 arcsec from the optical candidates (De Ugarte-Postigo et al., GCN 3192; Chen et al., GCN 3199). The [0.2-10] keV light curve in PC mode starts 2555 seconds after the HETE-II trigger (T0). The count rate is decaying following a power law with a slope of about 0.8 over a time interval of 40 ks. With the current data we do not see evidence of a break in the XRT light curve. A preliminary spectral fit to the PC data gives a power law photon index of 2.2 +/- 0.2 in the [0.5-10] keV band, with a column density of (2.5+/-0.6)E21 cm^-2 (the Galactic value is 1.8E20 cm^-2). The average unabsorbed 0.5-10 keV flux is about 6.2E-12 erg cm^-2 s^-1 (in the time range 2.5-43.5 ks from trigger).