Spin and Relativistic Phenomena Around Black Holes
  Since the seminal work of Penrose (1969) and Blandford & Znajek (1977), it
has been realized that black hole spin may be an important energy source in
astrophysics. The radio-loud/radio-quiet dichotomy in the AGN population is
usually attributed to differences in black hole spin, with correlations between
black hole spin and host galaxy morphology being hypothesized in order to
explain why radio-loud AGN occur in early-type galaxies. X-ray observations are
uniquely able to answer: Does black hole spin play a crucial role in powering
relativistic jets such as those seen from radio-loud active galactic nuclei
(AGN), Galactic microquasars, and Gamma-Ray Bursts? Indeed, the importance of
black hole spin goes beyond its role as a possible power source: the spin of a
supermassive black hole is a fossil record of its formation and subsequent
growth history.
