A note on polarized light from Magnetars

Understand

In a recent paper it is claimed that vacuum birefringence has been experimentally observed for the first time by measuring the degree of polarization of visible light from a Magnetar candidate, a neutron star with a magnetic field presumably as large as $B\sim 10^{13}$~G.

• The role of such a strong magnetic field is twofold.
• First, the surface of the star emits, at each point, polarized light with linear polarization correlated with the orientation of the magnetic field.
• Depending on the relative orientation of the magnetic axis of the star with the direction to the distant observer, a certain degree of polarization should be visible.