The recent discovery of X-ray reverberation in AGN has opened up a new path to probing the innermost regions around black holes in AGN. Lags due to light travel time between the reflected and direct emission components are of the order of a few tens of seconds, corresponding to a size scale of the order of just a few gravitational radii. Since the initial discovery in 2009, over a dozen more lags have now been seen, with the size of the lag scaling with black hole mass. While the initial discoveries involved time lags between two continuum bands, an exciting development has been the detections of lags between the direct continuum and the broad Fe Kalpha line, which has been seen in a handful of objects. Here, I will present a look at X-ray reverberation lags and the implications and prospects for probing the geometry of the inner emitting region around supermassive black holes.
There will be refreshments beforehand in 302 West Hall.