The multidimensional relativistic hydrodynamical code GENESIS has been used to obtain first results of 3D simulations of relativistic jets. We have studied the influence of a slight perturbation of the injection velocity field on the morphodynamics of otherwise axisymmetric relativistic jets.
We have studied the relativistic beamed outflow proposed to occur in the collapsar model of gamma-ray bursts. A jet forms as a consequence of an assumed energy deposition of ∼ 10 50 − 10 51 erg/s within a 30 • cone around the rotation axis of the progenitor star. The generated jet flow is strongly beamed ( < ∼ few degrees) and reaches the surface of the stellar progenitor (r ≈ 3 10 10 cm) intact. At break-out the maximum Lorentz factor of the jet flow is about 33. Simulations have been performed with the GENESIS multi-dimensional relativistic hydrodynamic code. Motivation and numerical setupVarious catastrophic collapse events have been proposed to explain the energies released in a gamma-ray burst (GRB) including compact binary system mergers [6,13], collapsars [18] and hypernovae [14]. These models all rely on a common engine, namely a stellar mass black hole (BH) which accretes several solar masses of matter from a disk (formed during a merger or by a non-spherical collapse). A fraction of the gravitational binding energy released by accretion is converted into a pair fireball. Provided the baryon load of the fireball is not too large, the baryons are accelerated together with the e + e − pairs to ultra-relativistic speeds (Lorentz factors > 10 2 ; [3]). The existence of such relativistic flows is supported by radio observations of GRB 980425 [8].The dynamics of spherically symmetric relativistic fireballs has been studied by several authors by means of 1D Lagrangian hydrodynamic simulations (e.g., [12]). It has been argued that the rapid temporal decay of several GRB afterglows is more consistent with the evolution of a relativistic jet after it slows down and spreads laterally than with a spherical blast wave [9]. The lack of a significant radio afterglow in GRB 990123 provides independent evidence for jet-like geometry [10]. Motivated by these observations and by the collapsar model of [11], we have simulated the propagation of jets from collapsars using relativistic hydrodynamics.In [11] the continued evolution of rotating helium stars, whose iron core collapse does not produce a successful outgoing shock but instead forms a BH surrounded 1
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