Axion minicluster halo limits from wide binary disruption

Abstract

Axionic dark matter can form miniclusters and minicluster halos (MCHs) from inhomogeneities in the early Universe. If MCHs are sufficiently massive, then their existence can be revealed by small-scale gravitational tidal perturbation to halolike wide binary star systems in the Galaxy. The observed population of the Milky Way’s wide-separation binaries with a≳0.1 parsec offer a sensitive test to dynamic evaporation from MCHs. Considering data from recent GAIA observations, we derive significant constraints on the MCH fraction of the Galactic dark matter halo. For several scenarios including dense MCHs and isolated minicluster models, these limits will apply to axionlike particles in the mass range ma∼10−15–10−12 eV and ma∼10−19–10−16 eV, respectively. Published by the American Physical Society 2025