New jet feature in the parsec-scale jet of the blazar OJ287 connected to the 2017 teraelectronvolt flaring activity

Abstract

In February 2017 the blazar OJ287, one of the best super-massive binary-black-hole-system candidates, was detected for the first time at very high energies (VHEs; E>100GeV) with the ground-based gamma-ray observatory VERITAS. Very high energy gamma rays are thought to be produced in the near vicinity of the central engine in active galactic nuclei. For this reason, and with the main goal of providing useful information for the characterization of the physical mechanisms connected with the observed teraelectronvolt flaring event, we investigate the parsec-scale source properties by means of high-resolution very long baseline interferometry observations. We use 86 GHz Global Millimeter-VLBI Array (GMVA) observations from 2015 to 2017 and combine them with additional multiwavelength radio observations at different frequencies from other monitoring programs. We investigate the source structure by modeling the brightness distribution with two-dimensional Gaussian components in the visibility plane. In the GMVA epoch following the source VHE activity, we find a new jet feature (labeled K) at about 0.2 mas from the core region and located in between two quasi-stationary components (labeled S1 and S2). Multiple periods of enhanced activity are detected at different radio frequencies before and during the VHE flaring state. Based on the findings of this work, we identify as a possible trigger for the VHE flaring emission during the early months of 2017 the passage of a new jet feature through a recollimation shock (represented by the model-fit component S1) in a region of the jet located at a de-projected distance of about 10 pc from the radio core.

5 pages, 3 figure, 1 table

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Cited by in corpus (9)

• The Black Hole Explorer: Motivation and Vision
• Unravelling the Innermost Jet Structure of OJ 287 with the First GMVA+ALMA Observations
• Blazars at Very High Energies: Emission Modelling
• Flare echos from relaxation shocks in perturbed relativistic jets
• Revealing a ribbon-like jet in OJ 287 with RadioAstron
• Unveiling the Bent Jet Structure and Polarization of OJ 287 at 1.7 GHz with Space VLBI
• The polarisation behaviour of OJ 287 viewed through radio, millimetre and optical observations between 2015 and 2017
• A high-resolution radio morphology and polarization of the kpc-scale X-ray jet of PKS 1127-145
• The First VHE Activity of OJ 287 and the Extragalactic Background Light