Probable detection of high-energy gamma-ray emission from OJ 287 during a major optical flare

We observed the BL Lac object OJ 287 with the CGRO/EGRET instrument as a target of opportunity triggered by an outburst in its visual intensity. OJ 287 is well known as a high-amplitude variable in the optical and radio domain, and recurrent outburst behavior at nominal 11.6-year intervals have led to speculation that there may be some deterministic mechanism underlying its activity cycle - in any case, it became active during late 1994, approximately 11.8 years subsequent to its previous outburst episode. OJ 287 had been considered an excellent candidate for detection at high-energy gamma-ray energies at earlier stages of the CGRO mission, but previous observations did not lead to a detection. We obtained a marginal detection of the source, which we argue is likely to be real given the precise coincidence with the peak of the optical flare. Temporal and spectral analysis are inconclusive due limited statistics. A broad-band spectral energy distribution for OJ 287 at the time of the flare is presented.