Periodic Fast Radio Bursts from Axion Emission by Cosmic Superstrings
  We propose that the periodic fast radio bursts of FRB 180916.J0158+65 are
sourced by axion emission (mass $m_{a} \sim 10^{-14}$ eV) from cosmic
superstrings. Some of the emitted axions are converted to photons by magnetic
fields as they travel along the line of sight to Earth. An impulsive burst of
axion emission generates a photon signal typically lasting for milliseconds and
varying with frequency in the observed manner. We find a range of parameters in
our cosmic string network model consistent with the properties of FRB
180916.J0158+65. We suggest followup gravitational wave observations to test
our model.
