2008/12/31 by J. L. Racusin, E. W. Liang, En‐Wei Liang +11 · 308 citations
Physics and Astronomy · #Afterglow #Astro and Planetary Science #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Gamma-ray burst #Gamma-ray bursts and supernovae #Jet (fluid) #Light curve #Mechanics #Physics #Power law #Spectral line #Swift #astro-ph
paper · pdf · doi:10.1088/0004-637x/698/1/43
published in The Astrophysical Journal 698(1), 43-74 (IOP Publishing) · 75 pages, 19 figures, 8 tables, accepted for publication in ApJ
arxiv created 2009/03/19 · openalex publication_date 2009/05/19 · arxiv updated 2010/03/19 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present a systematic temporal and spectral study of all Swift-X-ray Telescope observations of gamma-ray burst (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. Those X-ray light curves that do not show breaks or have breaks that are not consistent with one of the jet models are explored to place limits on the times of unseen jet breaks. The distribution of jet break times ranges from a few hours to a few weeks with a median of ~1 day, similar to what was found pre-Swift. On average, Swift GRBs have lower isotropic equivalent γ-ray energies, which in turn result in lower collimation corrected γ-ray energies than those of pre-Swift GRBs. Finally, we explore the implications for GRB jet geometry and energetics.