Searching for axions with time resolved pulsar polarimetry

Abstract

Pulsars possess strong dipole magnetic fields that can source axion fields through the axion-photon interaction. Pulsars may therefore be surrounded by axion field configurations oscillating with the pulsar's rotational period. These axions could be detected by observing their effect on the polarization of the pular's emission. In this paper, we use time resolved observations of the optical polarization of the Crab pulsar to place bounds on the axion-photon coupling, demonstrating the potential of time resolved pulsar birefringence in the search for axions.

Figures (2)

• Figure 1: Schematic geometry of the pulsar as seen from Earth. The rotation axis of the pulsar is denoted by ${\bf \Omega}$, the magnetic dipole moment by ${\bm \mu}$ and $\theta_v$ denotes the viewing angle, defined as the angle between the pulsar rotation axis and the observer’s line of sight.
• Figure 2: Oscillating linear polarization angle of the crab pulsar (blue) due to the axion field sourced by the pulsar's magnetic field $g_{a \gamma \gamma} = 1.5 \times 10^{-10}~{\rm GeV}$. The yellow curve shows the linear polarization angle of an identical pulsar with viewing angle $\theta_v = 10^{\circ}$.