2D hydrodynamic simulations of relativistic jets from collapsars

Using a collapsar progenitor model of MacFadyen & Woosley we have simulated the propagation of an axisymmetric relativistic jet through a collapsing rotating massive star. The jet forms as a consequence of an assumed constant or variable energy deposition in the range 1050 erg s−1 to 1051 erg s−1 within a 30° cone around the rotation axis. The jet flow is strongly beamed (≲ few degrees), spatially inhomogeneous, and time dependent. The jet reaches the surface of the stellar progenitor (R*=2.98×1010 cm) intact with a maximum Lorentz factor Γmax=33. After break-out the jet accelerates into the circumstellar medium, whose density is assumed to decrease exponentially and then being constant. Outside the star the flow also expands laterally (v∼c), but the beam remains very well collimated. At a distance of 2.54×R*, where we had to stop the simulation, the Lorentz factor has increased to 44.