2006/11/09 by G. Sato, Ryo Yamazaki, R. Yamazaki +23 · 5 citations
Physics and Astronomy · #Gamma-ray bursts and supernovae #astro-ph
paper · pdf · doi:10.1086/510610
published as Astrophys.J.657:359-366,2007 · 24 pages, 6 figures, accepted for publication in ApJ; minor revision
arxiv created 2006/11/09 · openalex publication_date 2007/03/01 · arxiv updated 2010/03/19 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We analyze Swift gamma-ray bursts (GRBs) and X-ray afterglows for three GRBs with spectroscopic redshift determinations: GRB 050401, XRF 050416a, and GRB 050525a. We find that the relation between spectral peak energy and isotropic energy of prompt emissions (the Amati relation) is consistent with that for the bursts observed in the pre- Swift era. However, we find that the X-ray afterglow light curves, which extend up to 10-70 days, show no sign of the jet break that is expected in the standard framework of collimated outflows. We do so by showing that none of the X-ray afterglow light curves in our sample satisfy the relation between the spectral and temporal indices that is predicted for the phase after jet break. The jet break time can be predicted by inverting the tight empirical relation between the peak energy of the spectrum and the collimation-corrected energy of the prompt emission (the Ghirlanda relation). We find that there are no temporal breaks within the predicted time intervals in X-ray band. This requires either that the Ghirlanda relation has a larger scatter than previously thought, that the temporal break in X-rays is masked by some additional source of X-ray emission, or that it does not happen for some unknown reason.