Aligned spin neutron star-black hole mergers: a gravitational waveform amplitude model

TL;DR

This paper develops a phenomenological amplitude model for gravitational waveforms from black hole-neutron star mergers, accounting for different tidal disruption scenarios, calibrated with extensive numerical simulations.

Contribution

It introduces a new amplitude model that captures various tidal disruption outcomes in black hole-neutron star mergers, calibrated with 134 numerical simulations.

Findings

Model accurately describes waveform amplitudes across disruption scenarios

Enables improved gravitational-wave detection and parameter estimation

Assists in understanding astrophysical phenomena like gamma-ray bursts

Abstract

The gravitational radiation emitted during the merger of a black hole with a neutron star is rather similar to the radiation from the merger of two black holes when the neutron star is not tidally disrupted. When tidal disruption occurs, gravitational waveforms can be broadly classified in two groups, depending on the spatial extent of the disrupted material. Extending previous work by some of us, here we present a phenomenological model for the gravitational waveform amplitude in the frequency domain encompassing the three possible outcomes of the merger: no tidal disruption, "mild" and "strong" tidal disruption. The model is calibrated to 134 general-relativistic numerical simulations of binaries where the black hole spin is either aligned or antialigned with the orbital angular momentum. All simulations were produced using the SACRA code and piecewise polytropic neutron star equations of state. The present model can be used to determine when black-hole binary waveforms are sufficient for gravitational-wave detection, to extract information on the equation of state from future gravitational-wave observations, to obtain more accurate estimates of black hole-neutron star merger event rates, and to determine the conditions under which these systems are plausible candidates as central engines of gamma-ray bursts, macronovae and kilonovae.