Jet breaks and Energetics of Swift GRB X-ray Afterglows

Understand

We present a systematic temporal and spectral study of all Swift-XRT observations of GRB afterglows discovered between 2005 January and 2007 December.

• After constructing and fitting all light curves and spectra to power-law models, we classify the components of each afterglow in terms of the canonical X-ray afterglow and test them against the closure relations of the forward shock models for a variety of parameter combinations.
• The closure relations are used to identify potential jet breaks with characteristics including the uniform jet model with and without lateral spreading and energy injection, and a power-law structured jet model, all with a range of parameters.
• With this technique, we survey the X-ray afterglows with strong evidence for jet breaks (~12% of our sample), and reveal cases of potential jet breaks that do not appear plainly from the light curve alone (another ~30%), leading to insight into the missing jet break problem.