TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3301 SUBJECT: GRB 050421: early Swift XRT analysis results DATE: 05/04/21 10:59:17 GMT FROM: David Burrows at PSU/Swift O. Godet, M. Goad, K. Page, J. Osborne (U. Leicester), D. N. Burrows (PSU), N. Gehrels (NASA/GSFC) report on behalf of the Swift XRT team: We have analyzed the Swift XRT data from the first orbit observation of GRB 050421. The refined coordinates are: RA(J2000) = 20h 29m 01.75s Dec(J2000) = +73d 39' 17.4" This position is 40 arcseconds from the BAT position given in GCN 3296 (Barbier et al 2005). We estimate a total uncertainty of 5 arcseconds radius (90% containment). We note that this refined position is 8.1 arcseconds from the XRT position reported in GCN 3296. Optical observers should re-check their images for sources in the new error circle. Our 0.2-10 keV light curve covers the interval 116-591 sec after the BAT trigger. It is well-fit with a broken powerlaw with initial slope of 0.9 +1.1/-1.6 breaking to a steeper slope of 3.3 +0.6/-0.3 after 147 +/-10 sec. All errors are 90% confidence. A single power law decline is not a good fit to the data. A preliminary spectral fit to the WT mode data gives a power law photon index of 1.23 +0.37/-0.34 (error at 90% confidence level) in the 0.3-10 keV band, assuming Galactic absorption (1.44 E21 cm^-2) and a possible excess in the absorption of 6 +4/-3 E21 cm^-2. The unabsorbed 0.3-10 keV flux is 8.5E-10 erg cm^-2 s^-1 in the interval 116-171 sec after the BAT trigger.