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

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.

Figure 1

Effective dimensionless tidal coefficient for DT effects (solid lines) and the adiabatic values (dashed lines) versus the orbital frequency $\mathrm{\Omega }$ and separation $r$.

Figure 2

Error budget for NS-BH NR simulations. We show for $q=2$ the phase differences $\delta \varphi$ (without alignment) with respect to the highest resolution simulation available using HO methods to quantify the sources of error due to finite resolution and mass escaping from the grid.

Figure 3

NS-BH coalescence. Upper panel: The (2,2) mode waveforms from the TEOB model of Eqs. (4) (red curve) and the NR simulation (blue curve) aligned in phase over the first five cycles. Lower panel: Phase differences between the NR simulation and tidal EOB models. The solid red curve corresponds to the TEOB waveform presented above. The blue shaded region indicates the NR error.

Figure 4

NS-NS coalescence. Same as Fig. 3, but considering a NR simulation [53] of a NS-NS binary with H4 EOS, $m_1=m_2=1.35M_{\odot }$ and $C_{\mathrm{N}\mathrm{S}}=0.1470$. The phase error on the NR waveform is $\sim 1\text{rad}$ at the peak in $|h_{22}|$ [53].