Although there [are]{} alternative explanations, such a periodicity is generally believed to [reveal]{} the binary’s orbital motion, which modulates accretion processes into the black holes, giving rise to periodic variations in disk emissions. To date systematic searches from large surveys have yielded more than one hundred quasar and AGN candidates with periodic variability, distributed over a wide redshift range up to $z\sim3$ (@Graham2015b [@Charisi2016; @Liu2016]). Due to the limited temporal baselines ($\lesssim$10 years), these detected rest-frame periods are confined to short timescales of several years or hundreds of days. There are also a number of quasars and nearby AGNs that were reported individually to exhibit periodicity based on long-term databases, including (but not limited to) OJ 287 ($z=0.31$; @Valtonen2008), NGC 4151 ($z=0.003$; @Guo2006 [@Bon2012]), and NGC 5548 ($z=0.017$; @Li2016 [@Bon2016]). OJ 287 is long-known to have strong radio emission while NGC 4151 and NGC 5548 [have relatively weak radio emission]{} (@Ho2002).

![image](ark120_lc_org.pdf){width="49.50000%"} ![image](ark120_lc.pdf){width="49.50000%"}

In this paper, we study the variability and analyze the possible periodicity in Ark 120 ($z=0.03271$[^1]), a nearby radio-quiet AGN with a radio-loudness $R\approx0.1$ (@Condon1998 [@Ho2002]). Ark 120 has been intensively observed and investigated in optical/UV (e.g., @Kollatschny1981a [@Kollatschny1981b; @Schulz1981; @Alloin1988; @Marziani1992; @Peterson1998; @Stanic2000; @Popovic2001; @Doroshenko2008; @Kuehn2008]) 