A long hard look on multiwavelength properties of blazar OJ 287

Abstract

We examined the behaviour of blazar OJ 287 based on 12 year observation data in optic, UV, X-ray, and gamma ray. The optical, UV, and X-ray data of OJ 287 were obtained from Swift archive, which provide more or less simultaneous optical–X-ray observations, while gamma ray data were obtained from Fermi archive. The occurrence of outburst episode in 2007 can be confirmed in Swift/UVOT data. In addition, episodes of significant brightening (possibly the outburst(s) of this decade) can also be seen in 2015–2016 and 2016–2017. Long-term flux variability in gamma ray and X-ray data is not always concurrent with those of optical and UV. Interestingly, the high peaks appeared almost simultaneous in optic, UV and X-ray in the episode of brightening in 2016–2017. X-ray spectral fittings show that non-thermal process predominates most of the X-ray spectra. Simultaneous optical–X-ray spectral fittings show the spectral evolution and suggest the combination of thermal and non-thermal component before brightening episode in 2015–2016. We obtained gamma ray spectra with broader peak at rather high frequency compared to that expected from simple synchrotron self-Compton mechanism. During brightening 2016–2017, the optical–X-ray fluxes are higher compared to those other periods. The shape of the X-ray and gamma ray spectra also have inverted trend than those of other periods.