Mass ejection in neutron star mergers

TL;DR

This study uses 3D Newtonian SPH simulations with realistic equations of state to analyze mass ejection during neutron star mergers, revealing that significant amounts of matter can be unbound, potentially explaining galactic r-process element abundance.

Contribution

First to demonstrate mass ejection in neutron star mergers using realistic LS-EOS in 3D Newtonian simulations, assessing sensitivity to model parameters.

Findings

Unbound mass ranges from 4e-3 to 4e-2 solar masses depending on initial spin.

Mass ejection could explain the entire galactic r-process material.

Results are robust across different model approximations.

Abstract

We present the results of 3D Newtonian SPH simulations of the merger of a neutron star binary. The microscopic properties of matter are described by the physical equation of state of Lattimer and Swesty (LS-EOS). To test for the robustness of our results we check the sensitivity to the approximations of our model as well as to the binary system parameters. The main and new result is that for the realistic LS-EOS, depending on the initial spin, between 4e-3 and 4e-2 solar masses of material become unbound. If, as suggested, large parts of this matter consist of r-process nuclei, neutron star mergers could account for the whole observed r-process material in the Galaxy.