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Dynamics and gravitational radiation of stable and unstable boson-star mergers

Bo-Xuan Ge1,*, Eugene A. Lim1,†, Ulrich Sperhake2,3,4, Tamara Evstafyeva2,5,‡, Daniela Cors2,§, Eloy de Jong1,∥, Robin Croft6,¶, and Thomas Helfer7,**

  • *Contact author: bo-xuan.ge@kcl.ac.uk
  • †Contact author: eugene.a.lim@gmail.com
  • ‡Contact author: te307@cam.ac.uk
  • §Contact author: dc889@cam.ac.uk
  • ∥Contact author: eloydejong93@gmail.com
  • Contact author: robin.croft@uniroma1.it
  • **Contact author: thomashelfer@live.de
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Phys. Rev. D 112, 124080 – Published 26 December, 2025

DOI: https://doi.org/10.1103/2dhs-phl4

Abstract

We explore the gravitational-wave emission from head-on collisions of equal-mass solitonic boson-star binaries from simulations spanning a two-dimensional parameter space, consisting of the central scalar-field amplitude of the stars and the solitonic potential parameter. We report the gravitational-wave energies emitted by boson-star binaries which, due to their combination of moderately high compactness with significant deformability, we often find to be louder by up to an order of magnitude than analogous black-hole collisions. The dependence of the radiated energy on the boson-star parameters exhibits striking needle-sharp features and discontinuous jumps to the value emitted by black-hole binaries. We explain these features in terms of the solitonic potential and the stability properties of the respective individual stars.

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Phys. Rev. D 112, 124080– Published 26 December, 2025
  • Received 28 February 2025
  • Accepted 13 November 2025
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