Neutrino-cooled accretion disks can form in the aftermath of neutron-star mergers as well as during the collapse of rapidly rotating massive stars (collapsars) and the accretion-induced collapse of rapidly rotating white dwarfs. Due to Pauli blocking as electrons become degenerate at sufficiently high accretion rates Ṁ, the resulting 'self-neutronization' of the dissociated accreting plasma makes these astrophysical systems promising sources of rapid neutron capture nucleosynthesis (the r-process). We present a one-dimensional general-relativistic, viscous-hydrodynamic model of neutrino-cooled accretion disks around black holes. With collapsars, super-collapsars and very massive star collapse in mind, we chart the composition of the accretion flow and systematically explore different radiatively efficient and inefficient accretion regimes with increasing M, across a vast parameter space of Ṁ 10^-6-10⁶ M_ \, s^-1, black hole masses of M_ 1 - 10⁴ M_ and dimensionless spins of χ_ [0, 1), as well as α-viscosity values of α 10^-3-1. We show that these accretion regimes are separated by characteristic thresholds Ṁ ₂₇₀ₑ that follow power laws M ₂₇₀ₑ M_^αα^β and that can be understood based on analytic approximations we derive. We find that outflows from such disks are promising sites of r-process nucleosynthesis up to M_ 3000 M_. These give rise to lanthanide-bearing 'red' super-kilonovae transients mostly for M_ 200-500 M_ and lanthanide suppressed 'blue' super-kilonovae for larger M_. Proton-rich outflows can develop specifically for large black hole masses (M_ 100 M_) in certain accretion regimes, which may give rise to proton-rich isotopes via the νp-process.
Hernández-Morales et al. (Thu,) studied this question.