The high-frequency quasi-periodic oscillations (HFQPOs) that punctuate the light curves of X-ray binary systems present a window onto the intrinsic properties of stellar-mass black holes and hence a testbed for general ...

Interactions between a supermassive black-hole binary and the surrounding accretion disc can both assist the binary inspiral and align the black-hole spins to the disc angular momentum. While binary migration is due to ...