Color Behavior Of BL Lacertae Object OJ 287 During Optical Outburst

TL;DR

This study analyzes the color behavior of BL Lac object OJ 287 during optical outbursts, confirming bluer-when-brighter chromatism and supporting the binary black hole model through observational data and simulations.

Contribution

It provides new observational evidence of color variation patterns and confirms the binary black hole model for OJ 287 using data analysis and simulations.

Findings

Bluer-when-brighter chromatism observed in OJ 287.

Amplitude of variation decreases with frequency.

Double-peaked outburst supports binary black hole model.

Abstract

This paper aims to study the color behavior of the BL Lac object OJ 287 during optical outburst. According to the revisit of the data from the OJ-94 monitoring project and the analysis the data obtained with the 60/90 cm Schmidt Telescope of NAOC, we found a bluer-when-brighter chromatism in this object. The amplitude of variation tends to decrease with the decrease of frequency. These results are consistent with the shock-in-jet model. We made some simulations and confirmed that both amplitude difference and time delay between variations at different wavelengths can result in the phenomenon of bluer-when-brighter. Our observations confirmed that OJ 287 underwent a double-peaked outburst after about 12 years from 1996, which provides further evidence for the binary black hole model in this object.