Institute for Advanced Study Informal Astrophysics Seminar

A microquasar is a black hole X-ray binary with outflowing jets. Conventional theory predicts alignment between three axes of a microquasar system: the black hole spin axis, the jet axis, and the rotational axis of the inner disk regions. However, these axes need not be aligned to the binary orbital axis. Understanding the origin and degree of spin-orbit misalignments is important for predicting black hole merger statistics and interpreting variability in X-ray binaries. The first part of the talk will question the origin of the >60 degree spin-orbit misalignment in V4641 Sgr, which cannot be explained by the standard supernova kick model. The second part of the talk will present a measurement of the inner disk inclination in GRO J1655-40, confirming the 15 degree spin-orbit misalignment implied by the jet and supporting the picture of viscous torques aligning the inner disk regions with the equatorial plane of a spinning black hole.