The jet in M87 from EVN observations
  One of the most intriguing open questions of today's astrophysics is the jet
physical properties and the location and the mechanisms for the production of
MeV, GeV, and TeV gamma-rays in AGN jets. M87 is a privileged laboratory for a
detailed study of the properties of jets, owing to its proximity, its massive
black hole, and its conspicuous emission at radio wavelengths and above. We
started on November 2009 a monitoring program with the e-EVN at 5 GHz. We
present here results of these multi-epoch observations and discuss the two
episodes of activity at energy E>100 GeV that occured in this period. One of
these observations was obtained at the same day of the first high energy flare.
We added to our results literature data obtained with the VLBI and VLA. A clear
change in the proper motion velocity of HST-1 is present at the epoch ~ 2005.5.
In the time range 1998 -- 2005.5 the apparent velocity is subluminal, and
superluminal (~ 2.7c) after 2005.5.
