2023/11/15 by Taya Govreen-Segal, Govreen-Segal, Taya, Ehud Nakar +1 · 3 citations
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #FOS: Physical sciences #Gamma-ray bursts and supernovae #High Energy Astrophysical Phenomena (astro-ph.HE) #Planetary Science and Exploration
paper · pdf · doi:10.48550/arxiv.2311.09297
openalex publication_date 2023/11/15 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We study, analytically and numerically, the structure and evolution of relativistic jetted blast waves that propagate in uniform media, such as those that generate afterglows of gamma-ray bursts. Similar to previous studies, we find that the evolution can be divided into two parts: (i) a pre-spreading phase, in which the jet core angle is roughly constant, θc,0, and the shock Lorentz factor along the axis, Γa, evolves as a part of the Blandford-Mckee solution, and (ii) a spreading phase, in which Γa drops exponentially with the radius and the core angle, θc, grows rapidly. Nevertheless, the jet remains collimated during the relativistic phase, where θc(Γaβa=1)≃ 0.4θc,01/3. The transition between the phases takes place when Γa≃ 0.2θc,0-1. We find that the "wings" of jets with initial "narrow" structure (\fracd log Eisodlog θ<-3 outside of the core, where Eiso is isotropic equivalent energy), start evolving during the pre-spreading phase. By the spreading phase these jets evolve to a self-similar profile, which is independent of the initial structure, where in the wings Γ(θ)∝θ-1.5 and Eiso(θ)∝ θ-2.6. Jets with initial "wide" structure roughly keep their initial profile during their entire evolution. We provide analytic description of the jet lateral profile evolution for a range of initial structures, as well as the evolution of Γa and θc. For off-axis GRBs, we present a relation between the initial jet structure and the light curve rising phase. Applying our model to GW170817, we find that initially the jet had θc,0=0.4-4.5~° and wings which are consistent with Eiso ∝ θ-3-θ-4.