Multiband optical variability of the blazar OJ 287 during its outbursts in 2015 -- 2016

TL;DR

This study presents extensive optical observations of the blazar OJ 287 during 2015-2016, capturing outbursts and analyzing flux, colour, and spectral variability to understand emission mechanisms.

Contribution

It provides a detailed multi-band optical monitoring campaign of OJ 287 during its outbursts, including the detection of a predicted large outburst and a secondary flare, with analysis of variability patterns.

Findings

Detected a large outburst in December 2015 predicted by models

Observed a second strong flare in March 2016

Analyzed flux, colour, and spectral variability across multiple timescales

Abstract

We present recent optical photometric observations of the blazar OJ 287 taken during September 2015 -- May 2016. Our intense observations of the blazar started in November 2015 and continued until May 2016 and included detection of the large optical outburst in December 2016 that was predicted using the binary black hole model for OJ 287. For our observing campaign, we used a total of 9 ground based optical telescopes of which one is in Japan, one is in India, three are in Bulgaria, one is in Serbia, one is in Georgia, and two are in the USA. These observations were carried out in 102 nights with a total of ~ 1000 image frames in BVRI bands, though the majority were in the R band. We detected a second comparably strong flare in March 2016. In addition, we investigated multi-band flux variations, colour variations, and spectral changes in the blazar on diverse timescales as they are useful in understanding the emission mechanisms. We briefly discuss the possible physical mechanisms most likely responsible for the observed flux, colour and spectral variability.