The Unique Blazar OJ 287 and its Massive Binary Black Hole Central
  Engine
  The bright blazar OJ 287 is the best-known candidate for hosting a nanohertz
gravitational wave (GW) emitting supermassive binary black hole (SMBBH) in the
present observable universe. The binary black hole (BBH) central engine model,
proposed by Lehto and Valtonen in 1996, was influenced by the two distinct
periodicities inferred from the optical light curve of OJ 287. The current
improved model employs an accurate general relativistic description to track
the trajectory of the secondary black hole (BH) which is crucial to predict the
inherent impact flares of OJ 287. The successful observations of three
predicted impact flares open up the possibility of using this BBH system to
test general relativity in a hitherto unexplored strong field regime.
Additionally, we briefly describe an on-going effort to interpret observations
of OJ 287 in a Bayesian framework.
