Fast radio bursts from axion stars moving through pulsar magnetospheres

We study the radio signals generated when an axion star enters the magnetosphere of a neutron star. As the axion star moves through the resonant region where the plasma-induced photon mass becomes equal to the axion mass, the axions can efficiently convert into photons, giving rise to an intense, transient radio signal. We show that a dense axion star with a mass ∼10-13 M composed of ∼10 μeV axions can account for most of the mysterious fast radio bursts.