Observations of Relativistically Broadened Iron K-Alpha Lines from AGNs

Relativistic X-ray reflection is commonly seen in many unobscured AGN. The iron K-alpha line is usually its most prominent feature. Observations of broad iron lines from ASCA to NUSTAR will be reviewed and their use in measuring the location and shape of the coronaoutlined. They also provide a measure of the spin of the black hole, which is often found to be high. Selection effects involved here will be discussed.