AX Per is a classical Symbiotic variable star. It's P_orb of 700d shows up well in the above light curve. The March/April 2009 'outburst' sees AX Per at it's brightest level since the 1988-1992 outburst. Previous outbursts occurred in 1888, 1925, 1950 & 1978.
Analysis with Peranso of 1294 observations shown in the light curve above (1990-2020) reveal a period of 685.4d +/- 6.3d, which is in good agreement with the 680.83d given in VSX.
The double peak (second peak at 645.6d after prewhitening) is a bit of a mystery though.