Spitzer Observation of the Predicted Eddington Flare from Blazar OJ 287

The binary black hole (BH) central engine description for the unique blazar OJ 287 predicted the next secondary BH impact induced flare to peak in the morning of July 31, 2019, within a specified ± 4.4 hour interval. This prediction was based on detailed General Relativistic modelling of the secondary BH trajectory around the primary BH and its accretion disk. We report the multi-epoch Spitzer observations of the expected flare between July 31 and September 6, 2019. Except for the higher base level flux at 3.55 and 4.49 microns than in the optical R-band, the flux behavior displays a strong similarity with the observed periastron flare from OJ 287 during September 2007. Comparing the two light curves we find that the Eddington flare came 2.7 hours ahead of time, but well within the expected time interval. Present observations firmly establish the presence of a nano-Hertz gravitational wave (GW) emitting spinning massive binary BH inspiraling along a general relativistic eccentric orbit in OJ 287. These GWs should be detectable by the International Pulsar Timing Array consortium during the Square Kilometre Array era. Further, Spitzer observations of the Eddington flare demonstrate the importance of hereditary contributions to GW emission in OJ 287. Finally, the multi-epoch Spitzer observations also provide the first observational constraints on the celebrated Black Hole No-Hair Theorem.