The Efficiency of Using Accretion Power of Kerr Black Holes

Ioana Duţan1,3 and Peter L. Biermann2,3 1University of Bucharest, Faculty of Physics Str. Atomiştilor, 405, RO-76900, Bucureşti-Mǎgurele, România 2University of Bonn Regina-Pacis-Weg, 3, D-53113, Bonn, Germany 3Max-Planck-Institute for Radioastronomy Auf dem Hűgel, 69, D-53121, Bonn, Germany [email protected]; [email protected] Abstra t The e ien y of a rapidly spinning Kerr bla k hole to turn a retion power into observable power an attain 32 per ent for the photon emission from the disk, as is well known, following the work of Novikov-PageThorne. But many a retion disks are now understood to be underluminous (L < LEdd), while still putting large amounts of energy into the jet. In this ase, the apparent e ien y of jets driven by the innermost a retion disk of a highly rotating Kerr bla k hole (a∗ = 0.999999) an rea h 96 per ent.