Authenticating the Presence of a Relativistic Massive Black Hole Binary
  in OJ 287 Using its General Relativity Centenary Flare: Improved Orbital
  Parameters
  Results from regular monitoring of relativistic compact binaries like PSR
1913+16 are consistent with the dominant (quadrupole) order emission of
gravitational waves (GWs). We show that observations associated with the binary
black hole central engine of blazar OJ 287 demand the inclusion of
gravitational radiation reaction effects beyond the quadrupolar order. It turns
out that even the effects of certain hereditary contributions to GW emission
are required to predict impact flare timings of OJ 287. We develop an approach
that incorporates this effect into the binary black hole model for OJ~287. This
allows us to demonstrate an excellent agreement between the observed impact
flare timings and those predicted from ten orbital cycles of the binary black
hole central engine model. The deduced rate of orbital period decay is nine
orders of magnitude higher than the observed rate in PSR 1913+16, demonstrating
again the relativistic nature of OJ 287's central engine. Finally, we argue
that precise timing of the predicted 2019 impact flare should allow a test of
the celebrated black hole "no-hair theorem" at the 10% level.
