Talk detail

Participant	Granot, Jonathan
Institution	Open University of Israel (and Hebrew University) - 1 University Road - Raanana - - Israel

Session	GRB4	Accepted	Yes	Order	7	Time	16:30 - 17:05
Talk	Oral abstract	Title	Magnetized relativistic outflows: effects of strong time dependence
Co-authors
Abstract	Once GRB jets transfer most of their energy to the shocked external medium their dynamics become relatively simpler, since the original outflow composition and radial profile are forgotten. Nevertheless, memory of the original jet angular profile persists for a long time. The non-spherical nature of the flow makes the dynamics non-trivial. These dynamics have important implications for inferring key physical parameters such as the energy, external density and shock microphysics parameters from afterglow observations. I will discuss recent progress in our understanding of the jet dynamics and the resulting afterglow lightcurves. In particular, the very modest jet lateral expansion seen in numerical simulations can be attributed to the modest jet initial half-opening angle, $\theta_0$, and is reproduced by simple analytic models if they are generalized so that they remain valid also for wide and sub-relativistic jets. Such analytic models predict an early phase of exponential lateral expansion only for jets that are initially extremely narrow ($\theta_0 \ll 0.05$). Finally, I will present recent hydrodynamics simulations of an afterglow jet propagating into a power-law external density profile, and discuss the implications for the jet break, off-axis lightcurves and the signature of the counter-jet in the late time radio lightcurves.

Session	GRB5	Accepted	Yes	Order	1	Time	14:00 - 14:30
Talk	Oral abstract	Title	GRB jet dynamics and afterglow lightcurves
Co-authors
Abstract	Once GRB jets transfer most of their energy to the shocked external medium their dynamics become relatively simpler, since the original outflow composition and radial profile are forgotten. Nevertheless, memory of the original jet angular profile persists for a long time. The non-spherical nature of the flow makes the dynamics non-trivial. These dynamics have important implications for inferring key physical parameters such as the energy, external density and shock microphysics parameters from afterglow observations. I will discuss recent progress in our understanding of the jet dynamics and the resulting afterglow lightcurves. In particular, the very modest jet lateral expansion seen in numerical simulations can be attributed to the modest jet initial half-opening angle, $\theta_0$, and is reproduced by simple analytic models if they are generalized so that they remain valid also for wide and sub-relativistic jets. Such analytic models predict an early phase of exponential lateral expansion only for jets that are initially extremely narrow ($\theta_0 \ll 0.05$). Finally, I will present recent hydrodynamics simulations of an afterglow jet propagating into a power-law external density profile, and discuss the implications for the jet break, off-axis lightcurves and the signature of the counter-jet in the late time radio lightcurves.