Tidal effects in binary neutron star coalescence

TL;DR

This study demonstrates that the tidal effective-one-body model accurately reproduces gravitational waveforms from binary neutron star coalescence up to contact, using analytical tidal corrections without additional calibration.

Contribution

It shows that the current tidal EOB model, with 2PN corrections, matches numerical relativity data without extra parameter tuning, confirming its effectiveness for neutron star mergers.

Findings

Tidal EOB model reproduces numerical data up to contact.

No additional calibration of tidal parameters needed.

2PN tidal corrections improve waveform accuracy.

Abstract

We compare dynamics and waveforms from binary neutron star coalescence as computed by new long-term ($\sim 10 $ orbits) numerical relativity simulations and by the tidal effective-one-body (EOB) model including analytical tidal corrections up to second post-Newtonian order (2PN). The current analytical knowledge encoded in the tidal EOB model is found to be sufficient to reproduce the numerical data up to contact and within their uncertainties. Remarkably, no calibration of any tidal EOB free parameters is required, beside those already fitted to binary black holes data. The inclusion of 2PN tidal corrections minimizes the differences with the numerical data, but it is not possible to significantly distinguish them from the leading-order tidal contribution. The presence of a relevant amplification of tidal effects is likely to be excluded, although it can appear as a consequence of numerical inaccuracies. We conclude that the tidally-completed effective-one-body model provides nowadays the most advanced and accurate tool for modelling gravitational waveforms from binary neutron star inspiral up to contact. This work also points out the importance of extensive tests to assess the uncertainties of the numerical data, and the potential need of new numerical strategies to perform accurate simulations.