Three-dimensional numerical simulations of structured GRB jets

Abstract

After the detection of GRB 170817A, the first unambiguous off-axis gamma-ray burst (GRB), several studies tried to understand the structure of GRB jets. The initial jet structure (directly produced by the central engine) can be partially preserved, or can be completely modified by the interaction with the environment. In this study, we perform three-dimensional, special relativistic hydrodynamics simulations of long GRB jets evolving through a massive progenitor star. Different jet scenarios were considered: Top-hat, Gaussian jets dominated by pressure or by kinetic energy, as well as a model of a supernova (SN) plus a jet both propagating through the progenitor. We found that, while propagating inside the progenitor star, jets with different initial structures are nearly indistinguishable. Kinetic dominated jets are faster and more collimated than pressure dominated jets. The dynamics of jets inside the progenitor star strongly depends on the presence of an associated SN, which can strongly decelerate the jet propagation. We show that the initial structure of GRB jets is preserved, or not, mainly depending on the jet duration (𝑡 𝑗 ) and on the jet break-out time (𝑡 bo ) from the dense environment. The initial structure is preserved in long-lasting jets (𝑡 𝑗 𝑡 bo ), while the interaction with the medium shapes short duration jets (𝑡 𝑗 𝑡 bo ). Future observations of a large sample of off-axis GRB will constrain the density stratification of the environment, the initial structure of the jet, and the physics of the central engine itself.

DeepGlow: An efficient neural network emulator of physical afterglow models for gamma-ray bursts and gravitational-wave events

“…In these cases, emulating a structured jet would be appropriate. These could be based on the numerical hydrodynamical simulations of relativistic jets with Gaussian profiles (Kumar & Granot 2003;Urrutia, De Colle, & López-Cámara 2022).…”