The Swift X-Ray Telescope

The Swift Gamma-Ray Explorer is designed to make prompt multiwavelength observations of Gamma-Ray Bursts (GRBs) and GRB Afterglows. The X-ray Telescope (XRT) provides key capabilities that permit Swift to determine GRB positions with a few arcseconds accuracy within 100 seconds of the burst onset. The <i>XRT</i> utilizes a superb mirror set built for <i>JET-X</i> and a state-of-the-art <i>XMM/EPIC MOS</i> CCD detector to provide a sensitive broad-band (0.2-10 keV) X-ray imager with effective area of 135 cm² at 1.5 keV, field of view of 23.6 x 23.6 arcminutes, and angular resolution of 18 arcseconds (HEW). The detection sensitivity is 2x10^-14 erg/cm²/s in 10⁴ seconds. The instrument is designed to provide automated source detection and position reporting within 5 seconds of target acquisition. It can also measure redshifts of GRBs for bursts with Fe line emission or other spectral features. The <i>XRT</i> will operate in an auto-exposure mode, adjusting the CCD readout mode automatically to optimize the science return for each frame as the source fades. The <i>XRT</i> will measure spectra and lightcurves of the GRB afterglow beginning about a minute after the burst and will follow each burst for days as it fades from view.