Ferreira, Jonathan

JEDs and SADs in X-ray Binaries.

Author list: Jonathan Ferreira, Pierre-Olivier Petrucci, Quentin Garnier

As proposed in Ferreira et al (2006), the conjecture is made that the innermost regions of accretion discs in XrBs is threaded by a large scale magnetic field of bipolar topology. Such a field is assumed to be near equipartition with the thermal pressure up to an outer transition radius r_J, and much below beyond that radius. A Jet Emitting Disc (hereafter JED) would thus be established below r_J and a Standard Accretion Disc (SAD) beyond. A JED is actually a new class of accretion disc solution with dynamical properties quite different from those of a standard disc. It allows the production of magnetically confined jets that can carry away a sizable fraction of the released accretion power, leading to a missing disc luminosity. Moreover, as for ADAFs, it exhibits three different thermal equilibrium branches at a given radius: two stable (cold and hot) and one intermediate unstable. The hot solution can be naturally associated with the hot X-ray corona generally invoked at the base of the jet in the hard states of microquasars.  It will be shown that such a configuration can naturally account for many observational features of microquasars, while providing a possible scenario for their hysteresis. Finally, the power carried by these Blandford & Payne type jets will be compared to that of Blandford & Znajek type.