Accurate numerical simulations of inspiralling binary neutron stars and their comparison with effective-one-body analytical models

TL;DR

This paper compares high-accuracy numerical simulations of binary neutron star inspirals with an extended effective-one-body analytical model, demonstrating the importance of calibrating higher-order tidal effects for precise gravitational waveform predictions.

Contribution

It introduces a calibrated tidal EOB model that accurately reproduces numerical waveforms up to merger, improving gravitational wave modeling for neutron star binaries.

Findings

Calibrated the EOB model's higher-order tidal parameter to match numerical waveforms.

EOB model with calibration outperforms uncalibrated models in waveform accuracy.

Analytical models without higher-order tidal effects show significant dephasing.

Abstract

Binary neutron-star systems represent one of the most promising sources of gravitational waves. In order to be able to extract important information, notably about the equation of state of matter at nuclear density, it is necessary to have in hands an accurate analytical model of the expected waveforms. Following our recent work, we here analyze more in detail two general-relativistic simulations spanning about 20 gravitational-wave cycles of the inspiral of equal-mass binary neutron stars with different compactnesses, and compare them with a tidal extension of the effective-one-body (EOB) analytical model. The latter tidally extended EOB model is analytically complete up to the 1.5 post-Newtonian level, and contains an analytically undetermined parameter representing a higher-order amplification of tidal effects. We find that, by calibrating this single parameter, the EOB model can reproduce, within the numerical error, the two numerical waveforms essentially up to the merger. By contrast, analytical models (either EOB, or Taylor-T4) that do not incorporate such a higher-order amplification of tidal effects, build a dephasing with respect to the numerical waveforms of several radians.