SIMBAD references

The collapse of massive rotating stellar cores and the associated accretion on to the newborn compact object is thought to power long gamma-ray bursts (GRBs). The physical scale and dynamics of the accretion disc are initially set by the angular momentum distribution in the progenitor, and the physical conditions make neutrino emission the main cooling agent in the flow. The formation and evolution of structure in these discs are potentially very relevant for the energy release and its time variability, which ultimately imprint on the observed GRB properties. To begin to characterize these, taking into account the three-dimensional nature of the problem, we have carried out an initial set of calculations of the collapse of rotating polytropic cores in three dimensions, making use of a pseudo-relativistic potential and a simplified cooling prescription. We focus on the effects of self-gravity and cooling on the overall morphology and evolution of the flow for a given rotation rate in the context of the collapsar model. For the typical cooling times expected in such a scenario, we observe the appearance of strong instabilities on the cooling time-scale following disc formation, which modulate the properties of the flow. Such instabilities, and the interaction they produce between the disc and the central object, lead to significant variability in the obtained mass accretion and energy-loss rates, which will likely translate into variations in the power of the relativistic outflow that ultimately results in a GRB.