Unequal mass binary neutron star mergers and multimessenger signals

TL;DR

This study investigates how unequal mass ratios in binary neutron star mergers affect gravitational wave signals, neutrino emissions, and ejecta properties, highlighting the importance of mass measurements for nuclear equation of state insights.

Contribution

It provides new insights into the impact of mass ratio and nuclear equations of state on merger outcomes, including ejecta and neutrino emissions, with implications for multimessenger astronomy.

Findings

Unequal mass mergers produce more neutron-rich ejecta.

Mass ratio influences gravitational wave signatures.

Ejecta properties depend on the nuclear equation of state.

Abstract

We study the merger of binary neutron stars with different mass ratios adopting three different realistic, microphysical nuclear equations of state, as well as incorporating neutrino cooling effects. In particular, we concentrate on the influence of the equation of state on the gravitational wave signature and also on its role, in combination with neutrino cooling, in determining the properties of the resulting hypermassive neutron star, of the neutrinos produced, and of the ejected material. The ejecta we find are consistent with other recent studies that find that small mass ratios produce more ejecta than equal mass cases (up to some limit) and this ejecta is more neutron rich. This trend indicates the importance with future kilonovae observations of measuring the individual masses of an associated binary neutron star system, presumably from concurrent gravitational wave observations, in order to be able to extract information about the nuclear equation of state