1995A&A...297L...9R

Nuclei of superluminal radio sources and of extragalactic γ-ray sources associated with compact beamed radio sources are characterized by relativistic ejections of ultrarelativistic particles. Assuming for the Hubble constant, Ho∼100km/s/Mpc, one finds from the apparent motion-redshift diagram that the bulk Lorentz factor γ is 3=<γ=<10. The spectrum of the source GRO J0516-609 is characterized by a strong peak in the 1-10MeV range, which can be explained as the signature of a broad blue shifted e± annihilation line amplified by the Doppler beaming effect. The typical densities of the e± are n±∼4.4x10⁸cm^–3. The high energy e± which escape after few light weeks will give rise to a new VLBI component. From COMPTEL and VLBI observations we show how it will be possible to determine the dynamical and geometrical characteristics of the relativistic e± beam when the apparent speed of the VLBI components of the associated compact radio source will be measured. Properties of powerful extragalactic radio sources can be understood if their nuclei eject two fluids, i.e. a relativistic e± beam responsible for superluminal radio sources and their γ-ray emission and a non-relativistic e- p jet responsible for the formation of kpc jets, hot spots and extended lobes.