Abstract:
We present the most extensive and well-sampled long-term multiband near-infrared (NIR) temporal and spectral
variability study of OJ 287, considered to be the best candidate binary supermassive black hole blazar. These
observations were made between 2007 December and 2021 November. The source underwent ∼2–2.5 mag
variations in the J, H, and Ks NIR bands. Over these long-term timescales there were no systematic trends in either
flux or spectral evolution with time or with the source’s flux states. However, on shorter timescales, there are
significant variations in flux and spectra indicative of strong changes during different activity states. The NIR
spectral energy distributions show diverse facets at each flux state, from the lowest to the highest. The spectra are,
in general, consistent with a power-law spectral profile (within 10%) and many of them indicate minor changes
(observationally insignificant) in the shift of the peak. The NIR spectra generally steepen during bright phases. We
briefly discuss these behaviors in the context of blazar emission scenarios/mechanisms, OJ 287ʼs well-known
traditional behavior, and implications for models of the source central engine invoked for its long-term optical
semiperiodic variations.
