2005/09/26 by Hideyuki Umeda, Nozomu Tominaga, Keiichi Maeda +2 · 2 citations
Physics and Astronomy · #Astro and Planetary Science #Gamma-ray bursts and supernovae #Pulsars and Gravitational Waves Research #astro-ph
paper · pdf · doi:10.1086/498136
published as Astrophys.J.633:L17-L20,2005 · 8 pages, 2 figures. Accepted for publication in the Astrophysical Journal (Letters)
arxiv created 2005/09/26 · openalex publication_date 2005/10/19 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
We investigate a "hypernova" model for gamma-ray bursts (GRBs), i.e., a massive C+O star model with relativistic jets. In this model, nonthermal precursors can be produced by the "first" relativistic shell ejected from the star. Main GRBs are produced behind the first shell by the collisions of several relativistic shells. They become visible to distant observers after the colliding region becomes optically thin. We examine six selected conditions using relativistic hydrodynamical simulations and simple analyses. Interestingly, our simulations show that subrelativistic ( v ~ 0.8 c ) jets from the central engine are sufficient to produce highly relativistic (Γ > 100) shells. We find that the relativistic shells from such a star can reproduce observed GRBs with certain conditions. Two conditions are especially important. One is the sufficiently long duration of the central engine, ≳100 s. The other is the existence of a dense shell somewhere behind the first shell. Under these conditions, both the existence and nonexistence of precursors, and the long delay between precursors and main GRBs, can be explained.