Speaker: Prof. David Burrows, Dept. of Astronomy & Astrophysics, Penn State niversity

 Time: 10:00AM, Thursday (June 19th)
 
 Location: 3rd floor, middle conf. room
 
　
 Abstract:  I will discuss some of the major accomplishments of the Swift X-ray Telescope in its first 3 years of operations, concentrating primarily on X-ray afterglows and the recent "naked-eye GRB", GRB 080319B. One of the major iscoveries of the Swift mission has been the discovery that X-ray flares are quite common in GRB afterglows. These flares have been widely interpreted as emission from late-time internal shocks, providing evidence for long-lived central engine activity, possibly from fall-back of material onto the accretion torus surrounding the central black hole. While this model provides a satisfactory explanation for most X-ray flares, it does not seem to explain all flares, and there is growing evidence pointing towards other mechanisms in some cases. At the same time, optical and X-ray afterglows do not always agree in their behavior, hinting that more complex models of the afterglows are needed. The recent "naked-eye" GRB 080319B provides strong evidence requiring a complex multi-jet model to explain the optical and X-ray afterglows, pointing towards one possible resolution of this problem. I will discuss our current understanding of this issue and will end with some possible future directions for research on gamma-ray burst afterglows.