  The Swift XRT has been observing GRB afterglows since December 23, 2004.
Three-quarters of these observations begin within 300 s of the burst onset,
providing an unprecendented look at the behavior of X-ray emission from GRB
afterglows in the first few hours after the burst. While most of the early
afterglows have smoothly declining lightcurves, a substantial fraction has
large X-ray flares on short time-scales. We suggest that these flares provide
support for models with extended central engine activity producing late-time
internal shocks.
