Impact of high-order tidal terms on binary neutron-star waveforms

Abstract

GW170817, the milestone gravitational-wave event originated from a binary neutron star merger, has allowed scientific community to place a constraint on the equation of state of neutron stars by extracting the leading-order, tidal-deformability term from the gravitational waveform. Here we incorporate tidal corrections to the gravitational-wave phase at next-to-leading and next-to-next-to-leading order, including the magnetic tidal Love numbers, tail effects, and the spin-tidal couplings recently computed in Tiziano Abdelsalhin [Phys. Rev. D 98, 104046 (2018)]. These effects have not yet been included in the waveform approximants for the analysis of GW170817. We provide a qualitative and quantitative analysis of the impact of these new terms by studying the parameter bias induced on events compatible with GW170817 assuming second-generation (advanced LIGO) and third-generation (Einstein Telescope) ground-based gravitational-wave interferometers. We find that including the tidal-tail term deteriorates the convergence properties of the post-Newtonian expansion in the relevant frequency range. We also find that the effect of magnetic tidal Love numbers could be measurable for an optimal GW170817 event with signal-to-noise ratio $\rho \approx 1750$ detected with the Einstein Telescope. On the same line, spin-tidal couplings may be relevant if mildly high-spin $\chi \gtrsim 0.1$ neutron star binaries exist in nature.