TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3805 SUBJECT: GRB 050814: XRT refined analysis DATE: 05/08/15 00:57:40 GMT FROM: David Morris at PSU/Swift-XRT D. C. Morris, D. N. Burrows, J. A. Kennea, J. L. Racusin (PSU), and N. Gehrels (GSFC) report on behalf of the Swift XRT team: We have analysed the first five orbits of data for GRB050814 (GCN 3799, Retter et al., 2005). Using xrtcentoid, the refined position is: RA(J2000) = 17h 36m 45.7s Dec(J2000) = +46d 20' 20.5" with an uncertainty of 8 arcsec. This is 5.4 arcsec from the original XRT position (GCN 3800, Morris et al., 2005). The initially distributed XRT position was based on the first orbit of PC data and may have been effected by a hot column at the position of the source. The refined position is calculated by analyzing several orbits of PC data, each taken at slightly different positions on the detector, so that the hot column in the first orbit of data is no longer a problem for the centroiding algorithm. The XRT began taking data at 11:41:15UT, 138 seconds after the BAT trigger. Both the windowed timing and photon counting data from the first orbit show a fading lightcurve consistent with a decay index of ~4. Photon counting data from subsequent orbits shows a flattening of the lightcurve near T+1000s to a decay index of ~0.1. The windowed timing spectrum (data from +165s to +383 after the BAT trigger) is well fit (reduced chi-sq of 1.22 for 72 dof) by a power law with neutral hydrogen somewhat larger than the galactic column density of 2.57e20: gamma=2.1 ± 0.1 NH=6.94e20 ± 2e18 The photon counting spectrum (from +383s through orbit 5) is well fit (reduced chi-sq of 0.61 for 31 dof) by a power law also with excess absorption: gamma=1.8 ± 0.2 NH=7.82e20 ± 7e18 The count rate at 20000s after the trigger is ~0.15 cts/s which converts to an unabsorbed flux of 4.76e-12 ergs cm^-2 s^-1. It should be noted that the early versions of the SDC data contained processing errors, likely due to earthlimb contamination, which may yet be contributing to some peculiarities in the PC lightcurve.