We present a numerical relativity study of eccentric mergers of equal-mass rotating mˉ=1 Proca stars, focusing on their gravitational-wave (GW) emission. By systematically varying key binary parameters, such as the initial orbital boost, which determines the orbital angular momentum, and the relative phase between the stars, we examine how the internal phase structure of the Proca field influences the merger dynamics and the properties of the emitted GWs. Our simulations demonstrate that the relative phase has paramount impact on the post-merger evolution, resulting in prompt black hole formation accompanied by a transient Proca remnant, the formation of a hypermassive mˉ=1 Proca star or even the emergence of a dynamically-unstable spinning mˉ=2 Proca star. Under certain conditions, the GW signal exhibits significant odd-modes (e.g., the ℓ=m=3 mode) that are absent in conventional black hole mergers, potentially serving as unique signatures of these exotic objects. Our findings offer new insights into the phenomenology of bosonic star mergers and the potential astrophysical role of ultralight bosonic fields.
Cite
@article{arxiv.2504.10235,
title = {Eccentric mergers of binary Proca stars},
author = {Gabriele Palloni and Nicolas Sanchis-Gual and José A. Font and Carlos Herdeiro and Eugen Radu},
journal= {arXiv preprint arXiv:2504.10235},
year = {2026}
}