Fig. 2: Linear polarization measurements of the bursts from FRB 20220912A detected by FAST.
From: Detecting extragalactic axion-like dark matter with polarization measurements of fast radio bursts

The observed polarization angle (PA, ϕobs) of each burst is depicted by a yellow point, the purple points represent the daily medians, and the light purple shaded area encompasses the 1σ confidence range. The dashed line represents the mean background 〈ϕbkg〉 = − 24.98°.