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In February 2017 the blazar OJ287, one of the best super-massivebinary-black-hole-system candidates, was detected for the first time at veryhigh energies (VHEs; E>100GeV) with the ground-based gamma-ray observatoryVERITAS. Very high energy gamma rays are thought to be produced in the nearvicinity of the central engine in active galactic nuclei. For this reason, andwith the main goal of providing useful information for the characterization ofthe physical mechanisms connected with the observed teraelectronvolt flaringevent, we investigate the parsec-scale source properties by means ofhigh-resolution very long baseline interferometry observations. We use 86 GHzGlobal Millimeter-VLBI Array (GMVA) observations from 2015 to 2017 and combinethem with additional multiwavelength radio observations at differentfrequencies from other monitoring programs. We investigate the source structureby modeling the brightness distribution with two-dimensional Gaussiancomponents in the visibility plane. In the GMVA epoch following the source VHEactivity, we find a new jet feature (labeled K) at about 0.2 mas from the coreregion and located in between two quasi-stationary components (labeled S1 andS2). Multiple periods of enhanced activity are detected at different radiofrequencies before and during the VHE flaring state. Based on the findings ofthis work, we identify as a possible trigger for the VHE flaring emissionduring the early months of 2017 the passage of a new jet feature through arecollimation shock (represented by the model-fit component S1) in a region ofthe jet located at a de-projected distance of about 10 pc from the radio core.

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