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T.J. Maccarone (SISSA)
I will discuss possible explanations and implications of recent results showing that the relativistic jets in GRO J 1655-40, V4641 Sgr, and probably Cygnus X-3 are not aligned perpendicular to the plane of their binary orbits. I will show that given reasonable assumptions about the initial conditions under which these systems were formed, the timescale for a black hole's spin to become aligned with that of the binary orbit is typically longer than the inferred maximum ages of the mass-donating stars in these systems. In particular, no high mass X-ray binaries should have had time for the spin axis of the black hole to have become aligned unless the initial value of the spin is very low. As a result, the Bardeen-Petterson effect becomes a natural candidate for explaining the observed misalignment of the jets relative to the orbital planes.
I will then discuss some of the implications of these results. First, these results provide cause for caution when using jet inclination angles to measure the binary orbit's inclination (as has been done, for example, to measure the mass of GRS 1915+105) or using binary plane inclination angles to estimate the speeds of relativistic jets. Secondly, in the case of severe misalignment, such as that seen in V 4641 Sgr where the binary plane and jet seem to be at least 36 degrees offset from one another, more exotic effects may be important. The companion star may then provide a substantial source of seed photons for inverse Comptonization in the jet, enhanced Compton reflection off the mass donating star, and may even cause eclipses of the jet and jet-star collisions which could lead to nuclear reactions on the surface on the star.
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Bulletin of the American Astronomical Society,
© 2003. The American Astronomical Soceity.