& 1935-1950 & 52 & & & &\
P83 & 8 & 42,392-44,226 & 1974-1979 & 36 & $15.0$ & & $0.687\pm0.087$ & $\phm{+}0.45\pm0.95$\
P89 & 2 & 43,426-47,414 & 1977-1988 & 74 & $7.0$ & & $0.607\pm0.297$ & $\phm{+}5.04\pm0.34$\
D99a1 & 9 & 43,963-50,818 & 1979-1998 & 25 & $14.3$ & & $1.132\pm0.070$ & $-5.04\pm0.90$\
D99a2 & 9 & 43,079-51,186 & 1976-1999 & 50 & $27.5$ & & $1.126\pm0.064$ & $-8.07\pm1.03$\
W92/97 & 10 & 47,534-52,282 & 1989-2002 & 37 & $20.0$ & & $0.719\pm0.017$ & $-0.79\pm0.28$\
R12 & 11 & 52,207-55,644 & 2001-2011 & 54 & & & $0.787\pm0.058$ & $-0.13\pm0.85$\
K14 & 12 & 52,237-54,319 & 2001-2007 & 67 & $8.3$ & & $0.903\pm0.030$ & $-0.34\pm0.40$\
C & 13 & 53,709-56,580 & 2005-2013 & 73 & & & $0.358\pm0.015$ & $\phm{+}6.51\pm0.22$\
H & 14 & 55,122-55,268 & 2009-2010 & 96 & 7.5 & & 1 & $-7.86\pm0.05$\
A & 15 & 55,949-58,345 & 2012-2018 & 476 & & & $0.808\pm0.005$ & $-2.97\pm0.07$ \[tab\_lc\]

Periodic brightness variability in long-term monitoring of active galactic nuclei (AGNs) is widely used to search for supermassive black hole (SMBH) binary candidates in modern time-domain surveys (e.g., @Graham2015a [@Graham2015b; @Liu2015; @Liu2016; @Charisi2016; @Zheng2016]). 