Multi-epoch, multi-frequency VLBI study of the parsec-scale jet in the blazar 3C 66A

TL;DR

This study uses multi-epoch, multi-frequency VLBI observations to analyze the complex kinematics of the parsec-scale jet in the blazar 3C 66A, revealing diverse motions and Doppler boosting effects.

Contribution

It provides the first detailed multi-frequency, multi-epoch VLBI analysis of 3C 66A's jet, uncovering complex motions and core non-stationarity.

Findings

Detection of inward and outward jet component motions.

Identification of the core based on spectral and compactness criteria.

Evidence of strong Doppler boosting in the jet.

Abstract

We present the observational results of the Gamma-ray blazar, 3C 66A, at 2.3, 8.4, and 22 GHz at 4 epochs during 2004-05 with the VLBA. The resulting images show an overall core-jet structure extending roughly to the south with two intermediate breaks occurring in the region near the core. By model-fitting to the visibility data, the northmost component, which is also the brightest, is identified as the core according to its relatively flat spectrum and its compactness. As combined with some previous results to investigate the proper motions of the jet components, it is found the kinematics of 3C 66A is quite complicated with components of inward and outward, subluminal and superluminal motions all detected in the radio structure. The superluminal motions indicate strong Doppler boosting exists in the jet. The apparent inward motions of the innermost components last for at least 10 years and could not be caused by new-born components. The possible reason could be non-stationarity of the core due to opacity change.