Gravitational Wave Signatures of Highly Compact Boson Star Binaries

TL;DR

This paper investigates the gravitational wave signals from merging highly compact boson star binaries, revealing how the post-merger waveforms depend on initial compactness and providing insights to distinguish these events from black hole or neutron star mergers.

Contribution

It extends previous studies by analyzing gravitational wave signatures of rotating boson star mergers and their dependence on initial compactness, offering new methods to identify such events.

Findings

Post-merger gravitational wave frequency depends on initial compactness.

Significant gravitational radiation emitted during the remnant's settling phase.

Analytical estimates of energy radiated after the merger.

Abstract

Solitonic boson stars are stable objects made of a complex scalar field with a compactness that can reach values comparable to that of neutron stars. A recent study of the collision of identical boson stars produced only non-rotating boson stars or black holes, suggesting that rotating boson stars may not form from binary mergers. Here we extend this study to include an analysis of the gravitational waves radiated during the coalescence of such a binary, which is crucial to distinguish these events from other binaries with LIGO and Virgo observations. Our studies reveal that the remnant's gravitational wave signature is mainly governed by its fundamental frequency as it settles down to a non-rotating boson star, emitting significant gravitational radiation during this post-merger state. We calculate how the waveforms and their post-merger frequencies depend on the compactness of the initial boson stars and estimate analytically the amount of energy radiated after the merger.