Long Term Multi-band Near Infra-Red Variability of the Blazar OJ 287 during 2007--2021

TL;DR

This extensive study of OJ 287 over 14 years reveals complex near-infrared variability with no long-term trends but significant short-term flux and spectral changes, providing insights into blazar emission mechanisms and the source's central engine.

Contribution

It provides the most comprehensive long-term multi-band NIR variability analysis of OJ 287, highlighting short-term activity and spectral behaviors relevant to blazar models.

Findings

No systematic long-term flux or spectral trends.

Significant short-term flux and spectral variations.

NIR spectra mostly follow a power-law profile with minor shifts.

Abstract

We present the most extensive and well-sampled long-term multi-band 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 December 2007 and November 2021. The source underwent ~ 2 -- 2.5 magnitude 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 steepens during bright phases. We briefly discuss these behaviors in the context of blazar emission scenarios/mechanisms, OJ 287's well-known traditional behavior, and implications for models of the source central engine invoked for its long-term optical semi-periodic variations.