Relativistic Jets from Collapsars

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 $\sim {10}^{50}-{10}^{51}$ erg/s within a ${30}^{\circ }$ cone around the rotation axis of the progenitor star. The generated jet flow is strongly beamed ($\text{la}$ few degrees) and reaches the surface of the stellar progenitor (r $\approx {310}^{10}$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.