The X-ray spectra of accreting black holes, both in active galactic nuclei and stellar mass sources, often show a broad skewed iron emission line. The red wing of the line is predominantly due to gravitational redshift and in some cases indicates that the emission originates from only 2 - 3 gravitational radii. Large light bending effects at such small radii affect the variability in a manner consistent with observation. The data provide strong evidence for rapidly spinning, Kerr, black holes. Recent data and future prospects will also be discussed.
BIOGRAPHICAL: Andy Fabian is a Royal Society Research Professor at the University of Cambridge, and head of its X-ray astronomy group. He obtained his Ph.D. at the University of London in 1972, moving to the Institute of Astronomy in Cambridge in 1973 and taking up his current post there in 1982. He is Vice Master of Darwin College Cambridge, a Fellow of the Royal Society and is a member of NASA's Chandra satellite project. He was awarded the Bruno Rossi Prize of the American Astronomical Society in 2001 jointly with Y. Tanaka.
He has broad interests in X-ray astronomy, having worked on data from most orbiting X-ray satellites. Currently his main interests are in clusters of galaxies and accreting black holes, both in active galaxies and Galactic ones. He has co-authored more than 500 research papers in refereed journals.