ar X iv : a st ro - p h / 95 12 09 3 v 1 1 4 D ec 1 99 5 BLACK HOLE , JET , AND DISK : THE UNIVERSAL ENGINE

In this paper I review the results of our ongoing project to investigate the coupling between accretion disk and radio jet in galactic nuclei and stellar mass black holes. We find a good correlation between the UV bump luminosity and the radio luminosities of AGN, which improves upon the usual [OIII]/radio correlations. Taking mass and energy conservation in the jet/disk system into account we can successfully model the correlation for radio-loud and radio-weak quasars. We find that jets are comparable in power to the accretion disk luminosity, and the difference between radioloud and radio-weak may correspond to two natural stages of the relativistic electron distribution – assuming that radio weak quasars have jets as well. The distribution of flatand steep-spectrum sources is explained by bulk Lorentz factors γj ∼ 5 − 10. The absence of radio-loud quasars below a critical optical luminosity coincides with the FR I/FR II break and could be explained by a powerdependent, “closing” torus. This points towards a different type of obscuring torus in radio-loud host galaxies which might be a consequence of past mergers (e.g. by the temporary formation of a binary black-hole). Interaction of the jet with the closing torus might in principle also help to make a jet radio-loud. Turning to stellar-mass black holes we find that galactic jet sources can be described with the same coupled jet/disk model as AGN which is suggestive of some kind of universal coupling between jet and accretion disk around