Modeling Mergers of Known Galactic Systems of Binary Neutron Stars

TL;DR

This paper models the merger of six known galactic binary neutron star systems, analyzing their dynamics, gravitational wave signals, and outcomes using open-source simulation tools and various equations of state.

Contribution

It provides detailed numerical simulations of known BNS mergers with unequal masses, including effects of different EOSs, using open-source codes and real galactic systems.

Findings

Gravitational wave signals characterized for each system.

Post-merger outcomes include hyper-massive neutron stars or black holes.

Effects of different EOSs on merger dynamics and outcomes.

Abstract

We present a study of the merger of six different known galactic systems of binary neutron stars (BNS) of unequal mass with a mass ratio between $0.75$ and $0.99$. Specifically, these systems are J1756-2251, J0737-3039A, J1906+0746, B1534+12, J0453+1559 and B1913+16. We follow the dynamics of the merger from the late stage of the inspiral process up to $\sim$ 20 ms after the system has merged, either to form a hyper-massive neutron star (NS) or a rotating black hole (BH), using a semi-realistic equation of state (EOS), namely the seven-segment piece-wise polytropic SLy with a thermal component. For the most extreme of these systems ($q=0.75$, J0453+1559), we also investigate the effects of different EOSs: APR4, H4, and MS1. Our numerical simulations are performed using only publicly available open source code such as, the Einstein Toolkit code deployed for the dynamical evolution and the LORENE code for the generation of the initial models. We show results on the gravitational wave signals, spectrogram and frequencies of the BNS after the merger and the BH properties in the two cases in which the system collapse within the simulated time.