Flare Activity of Blazar AO 0235+164

Abstract

Data analysis of long-term multi-frequency monitoring of active galactic nucleus (AGN) AO 0235+164 in the millimeter wavelength range are presented. Using the harmonic analysis of observational data, the presence of orbital and precession periods in the binary system from supermassive black holes (SBHs) is determined: T_orb ≈ 2 years and T_pr ≈ 8 years. The indicated periods are in agreement with similar periods found for other bright AGNs. In the AO 0235+164 system, other combinations of periodic components are also determined, which are possibly related to the nutation period. According to observational data of the development of flare phenomena at different frequencies, a cross-correlation analysis was performed and the shift delays of the flare times occurring at different wavelengths were determined. It was confirmed, by analogy with other AGNs, an empirical relation, to which the delays of flux variations with a frequency are obeyed having the form of the inverse logarithmic dependence. The nature of the delays can indicate the internal character of the variability of AGN emission fluxes obtained at frequencies of the centimeter and millimeter wavelength ranges. The hypothesis of jet activity of AGNs is confirmed, in which plasma formation, moving from the sources of ejection, becomes optically thin consistently on ever longer waves. Decreasing delays between frequencies for the flare in 2015 compared to the previous flare in 2008–2009 indicates a possible configuration variation in AO 0235+164 associated with decreasing in the angle between ejections and the direction to the observer.