Lessons from binary dynamics of inspiralling equal-mass boson-star mergers

TL;DR

This study uses numerical relativity to analyze gravitational waves from equal-mass boson-star mergers, highlighting waveform differences from black-hole systems and potential for improved detection and analysis methods.

Contribution

It characterizes waveform differences during inspiral, merger, and ringdown phases, and identifies unique features like subdominant modes in boson-star mergers.

Findings

Boson-star binaries show largest waveform deviations during late inspiral and merger.

Certain phase offsets excite subdominant odd m-multipoles absent in black-hole binaries.

Injections of boson-star signals can mimic black-hole signals, but consistency tests can distinguish them.

Abstract

We explore the gravitational-wave phenomenology of equal-mass inspiralling boson-star binaries using numerical relativity simulations. In particular, we characterise the waveform differences between binary boson-star and black-hole systems across (i) the early inspiral, by matching our waveforms to post-Newtonian expressions, (ii) merger, and (iii) late ringdown, by extracting the quasi-normal mode frequencies of the remnants. We find that boson-star binaries exhibit the largest deviations from comparable binary black-hole systems during the late inspiral and merger phases. Remarkably, for a subset of these equal-mass boson-star binaries (with certain phase offsets in the scalar-field profiles) we identify the excitation of subdominant odd $m$-multipoles in the gravitational-wave emission, absent in equal-mass nonspinning black-hole binaries. Despite differences in the phenomenology of binary boson-star and black-hole signals, injections of some boson-star signals into detector noise exhibit degeneracy with current waveform approximants. Building on these results, we demonstrate how inspiral-merger-ringdown consistency tests can overcome these degeneracies.