Temporal and Spectral Variability of OJ 287 before the April-June 2020 Outburst

We present the results of a temporal and spectral study of the BL Lacertae object OJ 287 in optical, UV, and X-ray bands with observations performed by <i>Swift</i> satellite during September 2019-March 2020. In this period, the source showed moderate variability characterized by variability amplitude of ∼22-31% in all the wavelengths on a short timescale, except the hard X-ray band which was variable by only ∼8%. We observed that the X-ray flux of the source was significantly dominated by the soft photons below 2 keV. Soft lags of ∼45 days were detected between the optical/UV and soft X-ray emissions, while there is no correlation between the hard X-rays and the lower energy bands indicating the presence of two emission components or electron populations. Although two components contribute to the X-ray emission, most of the 0.3-10 keV spectra were well fitted with an absorbed power-law model which outlines the dominance of synchrotron over inverse Compton (IC) mechanism. The X-ray spectra follow a weak “softer when brighter” trend.