X-ray signals converted from high-frequency gravitational waves emitted by spinning light primordial black hole dark matter

We investigate the detectability of high-frequency gravitational waves from the superradiance of light primordial black hole dark matter through photons converted in the Galactic magnetic field. We find that the signal is significantly enhanced in the X-ray frequency range around ${10}^{18}$Hz. For clustered initial conditions, future X-ray observations may detect the converted photons from primordial black holes in the mass range ${10}^{-15}{M}_{\odot }\sim {10}^{-13}{M}_{\odot }$. Our results indicate that future X-ray observations could provide a new probe of light primordial black hole dark matter through high-frequency gravitational waves.