Imaging and Variability Studies of CTA 102 during the 2016 January γ-ray Flare
Journal article, 2018

The γ-ray-bright blazar CTA 102 is studied using imaging (new 15 GHz and archival 43 GHz Very Long Baseline Array, VLBA data) and time variable optical flux density, polarization degree, and electric vector position angle (EVPA) spanning between 2015 June 1 and 2016 October 1, covering a prominent γ-ray flare during 2016 January. The pc-scale jet indicates expansion with oscillatory features up to 17 mas. Component proper motions are in the range 0.04-0.33 mas yr -1 with acceleration up to 1.2 mas followed by a slowing down beyond 1.5 mas. A jet bulk Lorentz factor ≥17.5, position angle of 128.°3, inclination angle ≤6. °6 and intrinsic half opening angle ≤1. °8 are derived from the VLBA data. These inferences are employed in a helical jet model to infer long-term variability in flux density, polarization degree, EVPA, and a rotation of the Stokes Q and U parameters. A core distance of r core,43 GHz = 22.9 pc, and a magnetic field strength at 1 pc and the core location of 1.57 G and 0.07 G, respectively, are inferred using the core-shift method. The study is useful in the context of estimating jet parameters and in offering clues to distinguish mechanisms responsible for variability over different timescales.

galaxies: active

relativistic processes

galaxies: jets

quasars: individual (CTA 102)

techniques: high angular resolution

Author

X. F. Li

Shanghai Astronomical Observatory

Chinese Academy of Sciences

ShanghaiTech University

P. Mohan

Shanghai Astronomical Observatory

T. An

Chinese Academy of Sciences

Shanghai Astronomical Observatory

X. Y. Hong

Shanghai Astronomical Observatory

Chinese Academy of Sciences

ShanghaiTech University

X. P. Cheng

Chinese Academy of Sciences

Shanghai Astronomical Observatory

Jun Yang

Chalmers, Space, Earth and Environment, Onsala Space Observatory, Onsala Space Observatory, Observation Support

Y. K. Zhang

Shanghai Astronomical Observatory

Chinese Academy of Sciences

Z. L. Zhang

Chinese Academy of Sciences

Shanghai Astronomical Observatory

Wei Zhao

Shanghai Astronomical Observatory

Chinese Academy of Sciences

Astrophysical Journal

0004-637X (ISSN) 1538-4357 (eISSN)

Vol. 854 1 17

Subject Categories

Astronomy, Astrophysics and Cosmology

Fusion, Plasma and Space Physics

DOI

10.3847/1538-4357/aaa5ac

More information

Latest update

4/18/2018