2000ApJ...531L.119A

Using a collapsar progenitor model of MacFadyen & Woosley, we have simulated the propagation of an axisymmetric jet through a collapsing rotating massive star with the GENESIS multidimensional relativistic hydrodynamic code. The jet forms as a consequence of an assumed (constant or variable) energy deposition in the range of 10⁵⁰-10⁵¹ ergs.s^–1 within a 30° cone around the rotation axis. The jet flow is strongly beamed (approximately less than a few degrees), spatially inhomogeneous, and time dependent. The jet reaches the surface of the stellar progenitor (R_*=2.98x10¹⁰ cm) intact. At breakout, the maximum Lorentz factor of the jet flow is 33. After breakout, the jet accelerates into the circumstellar medium, whose density is assumed to decrease exponentially and then become constant, ρ_ext=10^–5 g.cm^–3. Outside the star, the flow begins to expand laterally also (v∼c), but the beam remains very well collimated. At a distance of 2.54 R_*, where the simulation ends, the Lorentz factor has increased to 44.