Dark Matter-Independent Orbital Decay Bounds on Ultralight Bosons from OJ287

Ultralight bosons, predicted in scenarios beyond the Standard Model and viable dark matter (DM) candidates, can form superradiant clouds around spinning black holes influencing their dynamics. Using century-long monitored OJ287 supermassive black hole binary we set first DM-independent, dynamical constraints on their masses $\mu =(8.5-22)\times {10}^{-22}$ eV. These dynamical constraints, driven by boson cloud friction, are robust against DM-model uncertainties and offer a novel ultralight boson probe. We show that analogous superradiant dynamics across the cosmic population of supermassive black hole systems could help resolve final-parsec evolution stalling problem and imprint a detectable suppression and break in the gravitational wave background.