The jet in M87 from EVN observations

TL;DR

This study uses multi-epoch EVN observations of M87 to analyze jet activity and gamma-ray emission, revealing changes in jet velocity and linking radio activity to high-energy flares.

Contribution

It provides new multi-epoch radio observations of M87's jet, correlates jet velocity changes with gamma-ray activity, and enhances understanding of jet dynamics and high-energy emission mechanisms.

Findings

Change in jet proper motion velocity around 2005.5

Detection of superluminal motion (~2.7c) after 2005.5

Correlation between radio jet activity and gamma-ray flares

Abstract

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.