2003/05/08 by Rosalba Perna, Re'em Sari, Re’em Sari +1 · 2 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Cosmic Phenomena #Gamma-ray bursts and supernovae #astro-ph
paper · pdf · doi:10.1086/376772
published as Astrophys.J. 594 (2003) 379-384 · 14 pages, 3 figures; accepted to ApJ
arxiv created 2003/05/08 · openalex publication_date 2003/08/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
The two leading interpretations of achromatic breaks that are observed in the light curves of GRBs afterglow are (1) the manifestation of the edge of a jet, which has a roughly uniform energy profile and a sharp edge, and (2) a line-of-sight effect in jets with a variable energy profile. The first scenario requires the inner engine to produce a jet with a different opening angle each explosion, while the latter requires a standard engine. The physical structure of the jet is a crucial factor in understanding GRB progenitors, and therefore discriminating the two jet scenarios is particularly relevant. In the structured jet case, specific predictions can be made for the distribution of observed break angles θ br , while that distribution is arbitrary in the first scenario. We derive the theoretical distribution for the structured jet model. Specifically, we predict the most common angle to be about 0.12 rad, in rough agreement with the sample. If this agreement holds as the sample size increases, it would strengthen the case for the standard jet hypothesis. We show that a prediction of this model is that the average viewing angle is an increasing function of the survey sensitivity and in particular that a mission such as Swift will find the typical viewing angle to be about 0.3 rad. The local event rate predicted by this model is R GRB ( z = 0) ~ 0.5 Gpc -3 yr -1 .