Probing high frequency gravitational waves with pulsars

We study graviton-photon conversion in the magnetosphere of a pulsar and explore the possibility of detecting high frequency gravitational waves with pulsar observations. It is shown that conversion of one polarization mode of photons to that of gravitons can be enhanced significantly due to strong magnetic fields around a pulsar. We also derive the conservative upper bound on stochastic gravitational waves in a frequency range of 10⁸--10⁹ Hz and 10¹³--10²⁷ Hz by using data of observations of the Crab pulsar and the Geminga pulsar, respectively. Our method widely fills the gap among existing high frequency gravitational wave experiments and boosts the frequency frontier in gravitational wave observations.