Effects of Neutron-Star Dynamic Tides on Gravitational Waveforms within the Effective-One-Body Approach

Abstract

Extracting the unique information on ultradense nuclear matter from the gravitational waves emitted by merging neutron-star binaries requires robust theoretical models of the signal. We develop a novel effective-one-body waveform model that includes, for the first time, dynamic (instead of only adiabatic) tides of the neutron star as well as the merger signal for neutron-star-black-hole binaries. We demonstrate the importance of the dynamic tides by comparing our model against new numerical-relativity simulations of nonspinning neutron-star-black-hole binaries spanning more than 24 gravitational-wave cycles, and to other existing numerical simulations for double neutron-star systems. Furthermore, we derive an effective description that makes explicit the dependence of matter effects on two key parameters: tidal deformability and fundamental oscillation frequency. DOI: 10.1103/PhysRevLett.116.181101 Introduction.-Neutron stars (NSs) represent the strongest gravitational environment where matter can stably exist, with central densities several times higher than the density of an atomic nucleus (∼3 × 10 14 g cm −3 ). Under such great compression the ordinary structure of nuclear matter completely disintegrates; instead, novel phases of matter, new particles, or deconfined quarks may appear. The composition and equation of state (EOS) of ultradense NS matter remains a long-standing science frontier, despite recent constraints [1,2]. However, gravitational-wave (GW) observations of merging NS-NS or NS-black-hole (BH) binaries with ground-based interferometers (advanced LIGO [3], Virgo [4], and KAGRA [5]) will have a unique potential to probe the NS EOS, and possibly to combine this information with that from associated electromagnetic transients [6].Yet, the success of extracting the EOS information from the GW data requires highly accurate theoretical waveform models (templates) for matched filtering, where the data stream is cross-correlated with a template bank covering all physical parameter values. Building such templates requires a detailed understanding of the influence of NS

On the ambiguity in relativistic tidal deformability

“…The basic observation is that, when tidal deformabilities are included in a waveform model in a reasonable way, one can expect the ambiguity in relating back to the equation of state to be a single number that can be measured by fitting the model to a binary black hole waveform. More traditional semi-analytic methods (e.g., [33][34][35][36]) rely on numerical simulations of neutron star mergers for calibration. The method proposed here calibrates with vacuum (black hole) simulations, which are computationally cheaper and hence more practical to perform in the challenging early-inspiral regime.…”

Gravitational waves and mass ejecta from binary neutron star mergers: Effect of the mass ratio

“…In addition, the GW of BNS is almost entirely determined by the mass ratio q and the κ T 2 , because the binary total mass scales trivially in absence of tides and its de- pendency in the tidal waveform is hidden in the κ T 2 . Although other tidal polarizability parameters, corresponding to higher-than-quadrupole interactions, do play a role in the detailed modeling of the GW [69][70][71], the leading order κ T 2 encodes the main effect and it is the only tidal parameter measurable in GW searches. The coverage of the q-κ T 2 parameter space by our simulations is shown in Fig.…”

Impact of the tidal p−g instability on the gravitational wave signal from coalescing binary neutron stars

“…These include studies of the linear equilibrium tide [12,21,23,28,32,44] and the linear dynamical tide in non-rotating NSs [29,33,46,49,61] and rotating NSs [27,30,34]. The equilibrium and dynamical tide refer, respectively, to the quasi-static and resonant response of a star to a tidal field (see, e.g., [41]).…”