2026/07/23 by Carlos H. Coimbra-Araujo, Rita C. Anjos, Jonas P. Pereira +1
#astro-ph.HE #astro-ph.CO #gr-qc #hep-ph #hep-th
We study the production of ultra-high-energy particles via the Bañados--Silk--West (BSW) mechanism in the pre-merger phase of binary systems detected by LIGO-Virgo-KAGRA. By solving the geodesic equations for charged particles in magnetized Kerr spacetime with fields of B ∼ 1012--1014~G, we demonstrate that collisions near the horizon can achieve center-of-mass energies Ecm ∼ 1018-- 1020~eV, placing them firmly in the ultra-high-energy cosmic-ray (UHECR) range. We systematically explore the parameter space of merger remnants, varying black hole mass (M ∼ 20--150 M_\odot, characteristic of the binary black hole population), dimensionless spin (χf ∼ 0.7--0.9), magnetic field strength, and particle angular momenta. Our analysis reveals three distinct acceleration regimes: a gravity-dominated regime (B < 1012~G) with negligible magnetic enhancement; a transition regime (1012~G \lesssim B \lesssim 1013~G) where gravitational and magnetic effects compete; and a magnetic-dominated regime (B > 1013~G) where fields amplify collision energies by nearly an order of magnitude. For the 34 gravitational-wave events with high remnant spins (χf > 0.7), we compute the maximum achievable energies, finding that systems with χf \gtrsim 0.85 and M \gtrsim 100 M_\odot can reach Emax ∼ 1020~eV. Our results establish magnetized binary mergers, particularly black hole--neutron star systems and postmerger black hole remnants formed in binary neutron star coalescences, as promising sources of UHECRs and provide quantitative predictions linking gravitational-wave observables to particle acceleration efficiency.