r-Process Nucleosynthesis in Hot Accretion Disk Flows from Black Hole - Neutron Star Mergers

TL;DR

This study models the nucleosynthesis in outflows from black hole-neutron star mergers, showing that these environments can produce at least a weak r-process, with some cases generating a main r-process, driven by neutrino interactions.

Contribution

It provides a detailed numerical analysis of r-process element synthesis in merger-driven accretion disk outflows, highlighting the role of neutrino interactions in creating neutron-rich conditions.

Findings

At least a weak r-process is produced in the outflows.

Some cases exhibit a main r-process.

Neutrino interactions are crucial for neutron-rich conditions.

Abstract

We consider hot accretion disk outflows from black hole - neutron star mergers in the context of the nucleosynthesis they produce. We begin with a three dimensional numerical model of a black hole - neutron star merger and calculate the neutrino and antineutrino fluxes emitted from the resulting accretion disk. We then follow the element synthesis in material outflowing the disk along parameterized trajectories. We find that at least a weak r-process is produced, and in some cases a main r-process as well. The neutron-rich conditions required for this production of r-process nuclei stem directly from the interactions of the neutrinos emitted by the disk with the free neutrons and protons in the outflow.