The flaring activity of blazar AO 0235+164 during year 2021

TL;DR

This study investigates the 2021 flaring activity of blazar AO 0235+164, analyzing multi-wavelength data and jet dynamics to understand its origin, geometry, and relation to past flares.

Contribution

It provides new insights into the jet wobbling and precession, linking geometrical effects to the observed flaring behavior and jet component ejections.

Findings

Detection of two new jet components with different ejection directions

Confirmation of jet wobbling and precession consistent with observed flare patterns

Spectral energy distribution modeling supports geometrical explanations for flare differences

Abstract

Context. The blazar AO 0235+164, located at redshift $z=0.94$, has displayed interesting and repeating flaring activity in the past, the latest episodes occurring in 2008 and 2015. In 2020, the source brightened again, starting a new flaring episode that peaked in 2021. Aims. We study the origin and properties of the 2021 flare in relation to previous studies and the historical behavior of the source, in particular to the 2008 and 2015 flaring episodes. Methods. We analyze the multi-wavelength photo-polarimetric evolution of the source. From Very Long Baseline Array images, we derive the kinematic parameters of new components associated with the 2021 flare. We use this information to constrain a model for the spectral energy distribution of the emission during the flaring period. We propose an analytical geometric model to test whether the observed wobbling of the jet is consistent with precession. Results. We report the appearance of two new components that are ejected in a different direction than previously, confirming the wobbling of the jet. We find that the direction of ejection is consistent with that of a precessing jet.The derived period independently agrees with the values commonly found in the literature. Modeling of the spectral energy distribution further confirm that the differences between flares can be attributed to geometrical effects.