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arXiv · 2512.15242

Massive boson stars: Stability and GW emission in head-on mergers

Bo-Xuan Ge
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Abstract

We investigate quartically self-interacting massive boson stars by constructing equilibrium sequences and performing dynamical evolutions. The mass curve $M(|\phi_c|)$ along these sequences develops multiple extrema, yet stability changes only at the first maximum; configurations beyond it become highly compact and collapse under numerically induced perturbations, with near-critical models displaying a short-lived double-dive behaviour. Head-on collisions of equal-mass stars yield three distinct outcomes -- boson star remnants, black hole formation at contact, and collapse of each star to a black hole prior to contact. The associated gravitational-wave energies reflect a competition between increasing compactness, which enhances the efficiency of gravitational-wave emission, and decreasing tidal deformability, which suppresses merger asymmetries, and at large self-interaction strengths the collapse-before-contact branch exhibits a pronounced non-monotonic structure. The simulations reported here constitute a substantial catalogue of initial conditions and waveforms, providing a natural basis for constructing surrogate models capable of rapidly predicting gravitational-wave signals across an extended parameter space.

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Bo-Xuan Ge. 2025-12-17. Massive boson stars: Stability and GW emission in head-on mergers. https://doi.org/10.1103/y3t4-5t1q

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