Nonspinning black hole-neutron star mergers: a model for the amplitude of gravitational waveforms

TL;DR

This paper introduces a phenomenological model for the amplitude of gravitational waveforms from nonspinning black hole-neutron star mergers, accounting for different tidal disruption scenarios, calibrated with numerical simulations, aiding future gravitational wave data analysis.

Contribution

The paper presents a new model for gravitational waveform amplitude in black hole-neutron star mergers that includes tidal disruption effects and is calibrated with numerical relativity simulations.

Findings

Model covers no, mild, and strong tidal disruption cases.

Calibrated with general relativistic numerical simulations.

Provides analytical fits for KAGRA noise spectral density.

Abstract

Black hole-neutron star binary mergers display a much richer phenomenology than black hole-black hole mergers, even in the relatively simple case - considered in this paper - in which both the black hole and the neutron star are nonspinning. When the neutron star is tidally disrupted, the gravitational wave emission is radically different from the black hole-black hole case and it can be broadly classified in two groups, depending on the spatial extent of the disrupted material. We present a phenomenological model for the gravitational waveform amplitude in the frequency domain that encompasses the three possible outcomes of the merger: no tidal disruption, "mild", and "strong" tidal disruption. The model is calibrated to general relativistic numerical simulations using piecewise polytropic neutron star equations of state. It should prove useful to extract information on the nuclear equation of state from future gravitational-wave observations, and also to obtain more accurate estimates of black hole-neutron star merger event rates in second- and third-generation interferometric gravitational-wave detectors. We plan to extend and improve the model as longer and more accurate gravitational waveforms become available, and we will make it publicly available online as a Mathematica package. We also present in appendix analytical fits of the projected KAGRA noise spectral density, that should be useful in data analysis applications.