We report the initial results of our high-cadence monitoring program on the radio jet in the active galaxy M87 , obtained by the KVN and VERA Array ( KaVA ) at 22 GHz .
This is a pilot study that preceded a larger KaVA-M87 monitoring program , which is currently ongoing .
The pilot monitoring was mostly performed every two to three weeks from December 2013 to June 2014 , at a recording rate of 1 Gbps , obtaining the data for a total of 10 epochs .
We successfully obtained a sequence of good quality radio maps that revealed the rich structure of this jet from \lesssim 1 mas to 20 mas , corresponding to physical scales ( projected ) of \sim 0.1–2 pc ( or \sim 140–2800 Schwarzschild radii ) .
We detected superluminal motions at these scales , together with a trend of gradual acceleration .
The first evidence for such fast motions and acceleration near the jet base were obtained from recent VLBA studies at 43 GHz , and the fact that very similar kinematics are seen at a different frequency and time with a different instrument suggests these properties are fundamental characteristics of this jet .
This pilot program demonstrates that KaVA is a powerful VLBI array for studying the detailed structural evolution of the M87 jet and also other relativistic jets .