High-accuracy simulations of highly spinning binary neutron star systems

TL;DR

This paper presents high-accuracy numerical-relativity simulations of binary neutron star systems with high spins, revealing limitations of current waveform models and emphasizing the need for improved models for future gravitational-wave observations.

Contribution

The study provides a new set of high-resolution numerical-relativity simulations for highly spinning binary neutron stars, highlighting the inadequacy of existing models for such systems.

Findings

Current models fail to accurately describe high-spin neutron star mergers.

Biases in parameter estimation are evident when using existing models.

Simulations demonstrate convergence and reliability for testing waveform approximants.

Abstract

With an increasing number of expected gravitational-wave detections of binary neutron star mergers, it is essential that gravitational-wave models employed for the analysis of observational data are able to describe generic compact binary systems. This includes systems in which the individual neutron stars are millisecond pulsars for which spin effects become essential. In this work, we perform numerical-relativity simulations of binary neutron stars with aligned and anti-aligned spins within a range of dimensionless spins of $\chi \sim [-0.28,0.58]$. The simulations are performed with multiple resolutions, show a clear convergence order and, consequently, can be used to test existing waveform approximants. We find that for very high spins gravitational-wave models that have been employed for the interpretation of GW170817 and GW190425 are not capable of describing our numerical-relativity dataset. We verify through a full parameter estimation study in which clear biases in the estimate of the tidal deformability and effective spin are present. We hope that in preparation of the next gravitational-wave observing run of the Advanced LIGO and Advanced Virgo detectors our new set of numerical-relativity data can be used to support future developments of new gravitational-wave models.