de Pasquale, M and Oates, S and Evans, P and Schady, P and Page, M and Still, M and Breeveld, A and Zane, S (2008) Can a double component outflow explain the X-ray and Optical lightcurves of GRBs? In: 37th COSPAR Scientific Assembly. Held 13-20 July 2008, in Montreal, Canada. (pp. 667 - ?).
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There is an increasing sample of Swift GRBs that manifest evidence of "chromatic breaks", i.e. breaks that are present in the X-ray but absent in the optical. Modeling the X-ray and optical data, we find that in a significant fraction of these GRB afterglows the component producing the X-ray emission cannot be the same component that is responsible for the optical emission. We propose that these afterglow lightcurves are the result of a two-component jet, in which both components are energy-injected for the whole duration of the observation and the X-ray break is due to a jet break in the narrow outflow. This study has important consequences for the GRB community, since bursts with chromatic breaks provide us with an explanation for another surprising finding, the paucity of achromatic breaks at late times. We show that our model may explain the behaviour of GRB emission in both X-ray and optical bands. Therefore, it can be a radical and noteworthy alternative to the current interpretation for the "canonical" XRT and UVOT lightcurves, bearing fundamental implications for GRB physics.
|Title:||Can a double component outflow explain the X-ray and Optical lightcurves of GRBs?|
|UCL classification:||UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Space and Climate Physics|
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