Emergent nucleosynthesis from a 1.2 second long simulation of a black-hole accretion disk

TL;DR

This study presents a 1.2-second simulation of a black-hole accretion disk post-neutron star merger, revealing significant differences in nucleosynthesis outcomes compared to shorter simulations, emphasizing the importance of longer simulation durations.

Contribution

It provides the first long-duration (1.2 seconds) general relativistic neutrino radiation magnetohydrodynamic simulation of a black-hole accretion disk, highlighting the impact on r-process nucleosynthesis predictions.

Findings

Longer simulations include additional ejected mass affecting nucleosynthesis.

Emergent viscous ejecta conditions influence element formation.

Short simulations underestimate nucleosynthetic yields.

Abstract

We simulate a black-hole accretion disk system with full-transport general relativistic neutrino radiation magnetohydrodynamics (GR$\nu$RMHD) for 1.2 seconds. This system is likely to form after the merger of two compact objects and is thought to be a robust site of $r$-process nucleosynthesis. We consider the case of a black-hole accretion disk arising from the merger of two neutron stars. Our simulation time coincides with the nucleosynthesis timescale of the $r$ process ($\sim$ 1 second). Because these simulations are time consuming, it is common practice to run for `short' duration of approximately 0.1 to 0.3 seconds. We analyze the nucleosynthetic outflow from this system and compare the results between stopping at 0.12 and 1.2 seconds respectively. We find that the addition of mass ejected in the longer simulation as well as more favorable thermodynamic conditions from emergent viscous ejecta greatly impacts the nucleosynthetic outcome. We quantify the error in nucleosynthetic outcomes between short and long cuts.