Neutron tori and the origin of r-process elements

Neutrons released by dissociation of matter falling at high accretion rates into a black hole or neutron star accumulate in a dense 'neutron torus'. Matter in accretion disks around compact objects like those responsible for galactic X-ray sources may thus provide ideal conditions for classical rapid or r-process nucleosynthesis. Systems in which accretion powers an outflow from a region near the compact object might thereby enrich the interstellar medium in r-process elements. These elements are usually thought to originate in other stellar environments, such as helium shell-flash, supernovae and tidally dispersed neutron stars. The r-process mechanism considered in this paper was inspired by some ideas for manufacturing deuterium in pregalactic accretion disks. (author)