The evolution of black hole mass and angular momentum

We show that neither accretion nor angular momentum extraction is likely to lead to significant changes in the mass M1 or angular momentum parameter a* of a black hole in a binary system with realistic parameters. Current values of M1 and a* therefore probably reflect those at formation. We show further that sufficiently energetic jet ejection powered by the rotational energy of a black hole can stabilize mass transfer in systems with large adverse mass ratios, and even reduce the mass transfer rate to the point where the binary becomes transient.