Researchers have explored a mechanism for the production of ultra-high-energy particles in the pre-merger phases of binary systems detected by LIGO-Virgo-KAGRA. Using the Bañados-Silk-West (BSW) mechanism in the environment of magnetized Kerr black holes, they have shown that particle collisions near the event horizon can achieve center-of-mass energies of up to $10^{18}$–$10^{20}$ eV. These energies fall firmly within the range of ultra-high-energy cosmic rays (UHECRs), suggesting a new class of sources for these enigmatic phenomena.

The study modeled the geodesic trajectories of charged particles in a Kerr spacetime with magnetic fields of $B \sim 10^{12}$–$10^{14}$ G. The parameter space of merger remnants was systematically explored, varying black hole mass ($M \sim 20$–$150\,M_\odot$), dimensionless spin ($\chi_f \sim 0.7$–$0.9$), magnetic field strength, and particle angular momenta. Three distinct acceleration regimes were identified: a gravity-dominated regime (for $B < 10^{12}$ G), a transition regime where gravitational and magnetic effects compete ($10^{12} \text{ G} \lesssim B \lesssim 10^{13} \text{ G}$), and a magnetically dominated regime ($B > 10^{13}$ G) where fields amplify collision energies by nearly an order of magnitude.

For 34 gravitational-wave events with high remnant spins ($\chi_f > 0.7$), the maximum achievable energies were calculated. The results indicate that systems with $\chi_f \gtrsim 0.85$ and $M \gtrsim 100\,M_\odot$ can reach maximum energies of $E_{\mathrm{max}} \sim 10^{20}$ eV. These findings establish magnetized binary mergers, particularly black hole-neutron star systems and post-merger black hole remnants formed in binary neutron star coalescences, as promising sources of UHECRs. The study provides quantitative predictions linking gravitational-wave observables to particle acceleration efficiency, opening new avenues for understanding the origin of UHECRs.