New Limits on Axionic Dark Matter from the Magnetar PSR J1745-2900

Understand

Axions are a promising dark matter candidate that were motivated to solve the strong CP problem and that may also address the cosmological matter-antimatter asymmetry.

• Axion-photon conversion is possible in the presence of the strong magnetic fields, and the photon so produced will have energy equal to the axion mass.
• Here we report new limits on axionic dark matter obtained from radio spectra of the Galactic Center magnetar PSR J1745-2900.
• The magnetar has a magnetic field of $1.6\times10^{14}$ G that interacts with a dark matter density $2\times10^5$ to $2\times10^9$ times greater than the local dark matter encountered by terrestrial haloscopes, depending on the Galactic dark matter profile.