In a white dwarf acreting binary we would make distinction between thsoe with weak magnetic field that make an acretion disc and those with strong magentic fields where the material from the larger star gets funneled along the field lines. But in a black hole binary all of the energy is released at the acretiion disc. But what does that mean for the magentic field of the balck hole. Does it have a magentic field? If so how does that affect the way the matieral would be chanelled?