title: A dark jet dominates the power output of the stellar black hole Cygnus X-1.
abstract: Black holes undergoing accretion are thought to emit the bulk of their power in the X-ray band by releasing the gravitational potential energy of the infalling matter. At the same time, they are capable of producing highly collimated jets of energy and particles flowing out of the system with relativistic velocities. Here we show that the 10-solar-mass (10M(o)) black hole in the X-ray binary Cygnus X-1 (refs 3-5) is surrounded by a large-scale (approximately 5 pc in diameter) ring-like structure that appears to be inflated by the inner radio jet. We estimate that in order to sustain the observed emission of the ring, the jet of Cygnus X-1 has to carry a kinetic power that can be as high as the bolometric X-ray luminosity of the binary system. This result may imply that low-luminosity stellar-mass black holes as a whole dissipate the bulk of the liberated accretion power in the form of 'dark', radiatively inefficient relativistic outflows, rather than locally in the X-ray-emitting inflow.
authors.affiliation: Astronomical Institute Anton Pannekoek and Center for High Energy Astrophysics, University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands. egallo@science.uva.nl
authors.forename: Elena
authors.initials: E
authors.lastname: Gallo
authors.forename: Rob
authors.initials: R
authors.lastname: Fender
authors.forename: Christian
authors.initials: C
authors.lastname: Kaiser
authors.forename: David
authors.initials: D
authors.lastname: Russell
authors.forename: Raffaella
authors.initials: R
authors.lastname: Morganti
authors.forename: Tom
authors.initials: T
authors.lastname: Oosterloo
authors.forename: Sebastian
authors.initials: S
authors.lastname: Heinz