Black hole X-ray binary jets

Relativistic jets powered by stellar mass black holes in X-ray binaries appear to come in two types: steady outflows associated with hard X-ray states and large scale discrete ejections associated with transient outbursts. We show that the broadband radio spectrum of a `quiescent' stellar mass black hole closely resembles that of canonical hard state sources emitting at four orders of magnitude higher X-ray levels, suggesting that a relativistic outflow is being formed down to at least a few 10^(-6) times the Eddington X-ray luminosity. We further report on the discovery of a low surface brightness radio nebula around the stellar black hole in Cyg X-1, and discuss how it can be used as an effective calorimeter for the jet kinetic power.