ASAS-SN (top and middle) and ZTF photometry (bottom) of TOI-521. The light curves are linearly detrended to remove the effect of the high proper motions of the star. The right panel of each plot shows the GLS periodogram, highlighting the 1% (dashed line) and 10% (dotted line) FAP levels. The most significant frequency is marked with a red vertical line. None of the ASAS-SN peaks is highly significant, while for ZTF many peaks and aliases are identified, probably due to the irregular sampling.