A New Amplitude Model for NSBH Coalescences

Abstract

[eng] Since their first detection in 2015, the field of gravitational-wave astronomy has experienced remarkable growth and shown a very promising potential as a new way of learning more about the cosmos. To date, about 100 gravitational-wave signals originating from compact binary coalescences have been detected. One particular type of these coalescences are mixed binary systems composed of a black hole and a neutron star, often referred to as NSBH mergers. These systems show a phenomenology that ranges from subtle deviations from the binary black hole case to complete tidal disruption of the neutron star, resulting in a sudden shut-off of the gravitational-wave signal and possible electromagnetic counterparts such as short gamma-ray bursts. The prospect of being associated to electromagnetic counterparts makes these systems very promising sources of multi-messenger astronomy, from which we could obtain relevant information about the states of matter inside neutron stars or even the fundamental nature of the cosmos. What is more, these mergers could provide such information even if no electromagnetic counterpart can be detected, because different values of tidal deformabilities can result in a remarkably different morphologies [1]. Furthermore, tidal corrections depend on source-frame masses, breaking the usual distance-redshift degeneracy affecting binary black hole mergers [2]: this makes binaries hosting neutron stars promising dark sirens for the determination of Hubble’s constant. An essential component of the current methods for gravitational-wave detection and analysis is the availability of accurate waveform models that allow matching the signal with its physical parameters. This thesis presents the first stage of development of a new computationally efficient phenomenological amplitude model for neutron star – black hole coalescences that improves upon its predecessors by updating the binary black hole baseline, including higher order tidal corrections, and using an increased number of simulations for its accurate calibration to numerical relativity. After further improvements, we expect that the model will be a useful tool in the analysis of future observations of NSBH.