Swift XRT Observations of X-ray Flares in GRB Afterglows

David N. Burrows, P. Romano, O. Godet, A. Falcone, C. Pagani, G. Cusumano, S. Campana, G. Chincarini, J. E. Hill, P. Giommi, M. R. Goad, J. A. Kennea, S. Kobayashi, P. Meszaros, J. A. Nousek, J. P. Osborne, P. T. O'Brien, K. L. Page, G. Tagliaferri, B. Zhang, the Swift XRT team

Published 2005-11-01Version 2

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.