Bound Debris Expulsion from Neutron Star Merger Remnants

TL;DR

This paper investigates the origin and dynamics of bound debris expelled during neutron star mergers, focusing on how the debris's initial location and escape pathways influence the resulting disk mass and structure.

Contribution

It introduces a method combining tracer particles and fluid data to analyze debris origin, escape paths, and orbital divergence in neutron star merger simulations.

Findings

Identifies debris origin within neutron stars.

Maps debris escape pathways and timing.

Analyzes factors influencing disk mass formation.

Abstract

Many studies have found that neutron star mergers leave a fraction of the stars' mass in bound orbits surrounding the resulting massive neutron star or black hole. This mass is a site of $r-$ process nucleosynthesis and can generate a wind that contributes to a kilonova. However, comparatively little is known about the dynamics determining its mass or initial structure. Here we begin to investigate these questions, starting with the origin of the disk mass. Using tracer particle as well as discretized fluid data from numerical simulations, we identify where in the neutron stars the debris came from, the paths it takes in order to escape from the neutron stars' interiors, and the times and locations at which its orbital properties diverge from those of neighboring fluid elements that end up remaining in the merged neutron star.