2014/06/30 by O. Just, Oliver Just, A. Bauswein +8 · 607 citations
Physics and Astronomy · #Accretion (finance) #Astrophysical Phenomena and Observations #Astrophysics #Ejecta #Gamma-ray bursts and supernovae #Kilonova #Neutrino #Neutron star #Nuclear physics #Nucleosynthesis #Physics #Pulsars and Gravitational Waves Research #Supernova #Torus #astro-ph.SR
paper · pdf · doi:10.1093/mnras/stv009
published in Monthly Notices of the Royal Astronomical Society 448(1), 541-567 (Oxford University Press) · 30 pages, 22 figures; revised version, accepted by MNRAS; appendix added with test results for neutrino transport
arxiv created 2015/01/07 · openalex publication_date 2015/02/05 · arxiv updated 2015/06/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present the first comprehensive study of r-process element nucleosynthesis in the ejecta of compact binary mergers (CBMs) and their relic black hole (BH)–torus systems. The evolution of the BH–accretion tori is simulated for seconds with a Newtonian hydrodynamics code including viscosity effects, pseudo-Newtonian gravity for rotating BHs, and an energy-dependent two-moment closure scheme for the transport of electron neutrinos and antineutrinos. The investigated cases are guided by relativistic double neutron star (NS–NS) and NS–BH merger models, producing ∼3–6 M⊙ BHs with rotation parameters of ABH ∼ 0.8 and tori of 0.03–0.3 M⊙. Our nucleosynthesis analysis includes the dynamical (prompt) ejecta expelled during the CBM phase and the neutrino and viscously driven outflows of the relic BH–torus systems. While typically ∼20–25 per cent of the initial accretion-torus mass are lost by viscously driven outflows, neutrino-powered winds contribute at most another ∼1 per cent, but neutrino heating enhances the viscous ejecta significantly. Since BH–torus ejecta possess a wide distribution of electron fractions (0.1–0.6) and entropies, they produce heavy elements from A ∼ 80 up to the actinides, with relative contributions of A ≳ 130 nuclei being subdominant and sensitively dependent on BH and torus masses and the exact treatment of shear viscosity. The combined ejecta of CBM and BH–torus phases can reproduce the solar abundances amazingly well for A ≳ 90. Varying contributions of the torus ejecta might account for observed variations of lighter elements with 40 ≤ Z ≤ 56 relative to heavier ones, and a considerable reduction of the prompt ejecta compared to the torus ejecta, e.g. in highly asymmetric NS–BH mergers, might explain the composition of heavy-element deficient stars.