Burrows, David N.David N.BurrowsKennea, J. A.J. A.KenneaAbbey, A. F.A. F.AbbeyCapalbi, MilviaMilviaCapalbiGiommi, PaoloPaoloGiommiPerri, MatteoMatteoPerri2020-09-172020-09-172007-09-01https://hdl.handle.net/20.500.13025/929UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XV. Edited by Siegmund, Oswald H. Proceedings of the SPIE, Volume 6686, article id. 668607, (2007).We present science highlights and performance from the Swift X-ray Telescope (XRT), which was launched on November 20, 2004. The XRT covers the 0.2-10 keV band, and spends most of its time observing gamma-ray burst (GRB) afterglows, though it has also performed observations of many other objects. By mid-August 2007, the XRT had observed over 220 GRB afterglows, detecting about 96% of them. The XRT positions enable followup ground-based optical observations, with roughly 60% of the afterglows detected at optical or near IR wavelengths. Redshifts are measured for 33% of X-ray afterglows. Science highlights include the discovery of flaring behavior at quite late times, with implications for GRB central engines; localization of short GRBs, leading to observational support for compact merger progenitors for this class of bursts; a mysterious plateau phase to GRB afterglows; as well as many other interesting observations such as X-ray emission from comets, novae, galactic transients, and other objects.conference paper10.1117/12.735130http://adsabs.harvard.edu/abs/2007SPIE.6686E...7B2007SPIE.6686E...7B