Exploring tidal effects of coalescing binary neutron stars in numerical relativity

TL;DR

This paper analyzes gravitational waves from binary neutron star mergers using numerical relativity, comparing results with post-Newtonian and effective-one-body models, and highlights the importance of resolution extrapolation for accurate waveform phase predictions.

Contribution

It introduces a method for extrapolating numerical relativity waveforms to improve phase accuracy and compares these with analytical models during inspiral.

Findings

Numerical relativity phases agree with PN and EOB models during most of inspiral.

Extrapolation reduces phase discrepancies to within 1-3 radians in last 15 cycles.

Tidal effects are underestimated by PN and EOB in the final inspiral stage.

Abstract

We study gravitational waves emitted in the late inspiral stage of binary neutron stars by analyzing the waveform obtained in numerical-relativity simulations. For deriving the physical gravitational waveforms from the numerical results, the resolution extrapolation plays an essential role for our simulations. The extrapolated gravitational-wave phases are compared with those calculated in the post-Newtonian (PN) and effective-one-body (EOB) formalisms including corrections of tidal effects. We show that the extrapolated gravitational-wave phases in numerical relativity agree well with those by the PN and EOB calculations for most of the inspiral stage except for a tidally-dominated, final inspiral stage, in which the PN and EOB results underestimate the tidal effects. Nevertheless, the accumulated phase difference between our extrapolated results and the results by the PN/EOB calculations is at most 1--3 radian in the last 15 cycles.