ANGULAR MOMENTUM ROLE IN THE HYPERCRITICAL ACCRETION OF BINARY-DRIVEN HYPERNOVAE

Abstract

Here, the induced gravitational collapse paradigm explains a class of energetic, ${E}_{{\\rm{iso}}}\\gtrsim {10}^{52}$ erg, long-duration gamma-ray bursts (GRBs) associated with Ic supernovae, recently named binary-driven hypernovae. The progenitor is a tight binary system formed of a carbon–oxygen (CO) core and a neutron star (NS) companion. The supernova ejecta of the exploding CO core trigger a hypercritical accretion process onto the NS, which reaches the critical mass in a few seconds, and gravitationally collapses to a black hole, emitting a GRB. In our previous simulations of this process, we adopted a spherically symmetric approximation to compute the features of the hypercritical accretion process. We here present the first estimates of the angular momentum transported by the supernova ejecta, ${L}_{{\\rm{acc}}},$ and perform numerical simulations of the angular momentum transfer to the NS during the hyperaccretion process in full general relativity. We show that the NS (1) reaches either the mass-shedding limit or the secular axisymmetric instability in a few seconds depending on its initial mass, (2) reaches a maximum dimensionless angular momentum value, ${[{cJ}/({{GM}}^{2})]}_{{\\rm{max}}}\\approx 0.7$, and (3) can support less angular momentum than the one transported by supernova ejecta, ${L}_{{\\rm{acc}}}\\gt {J}_{{\\rm{NS,max}}},$ hence there is an angular momentum excess that necessarily leads to jetted emission.