Radio Signals from Axion Dark Matter Conversion in Neutron Star Magnetospheres

Understand

We show that axion dark matter (DM) may be detectable through narrow radio lines emitted from neutron stars.

• The neutron star magnetosphere hosts a strong magnetic field and a plasma frequency that increases towards the neutron star surface.
• As the axions pass through the magnetosphere, they can resonantly convert into radio photons in a narrow region around the radius at which the plasma frequency equals the axion mass.
• The bandwidth of the signal is set by the small DM velocity dispersion far away from the neutron star.