  We are exploring the viability of the collapsar model for long-soft gamma-ray
bursts. For this we perform state-of-the-art general relativistic hydrodynamic
simulations in a dynamically evolving space-time with the CoCoNuT code. We
start from massive low metallicity stellar models evolved up to core
gravitational instability, and then follow the subsequent evolution until the
system collapses forming a compact remnant. A preliminary study of the collapse
outcome is performed by varying the typical parameters of the scenario, such as
the initial stellar mass, metallicity, and rotational profile of the stellar
progenitor. 1D models (without rotation) have been used to test our newly
developed neutrino leakage scheme. This is a fundamental piece of our approach
as it allows the central remnant (in all cases considered, a metastable
high-mass neutron star) to cool down, eventually collapsing to a black hole. In
two dimensions, we show that sufficiently fast rotating cores lead to the
formation of Kerr black holes, due to the fall-back of matter surrounding the
compact remnant, which has not been successfully unbounded by a precedent
supernova shock.
