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AGN Accretion Disk Reverberation Mapping

February 16, 2017

When: February 16, 2017 3:30AM

Rick Edelson

University of Maryland

Because active galactic nuclei (AGN) are too distant to image, their variability provides perhaps our most powerful probe of their central engines. The technique of "reverberation mapping" was originally developed to study the ionized gas surrounding the nucleus, and decades of trying to adapt this approach to study the smaller but physically more important central engines have yielded marginal results at best. However, recent high cadence monitoring across the X-ray, UV and optical regimes with Swift and ground-based observatories such as LCO has allowed a breakthrough: interband lags have now clearly been detected both within the UV/optical and between the X-rays and UV in NGC 5548 and NGC 4151. These results are not compatible with the standard thin accretion disk/reprocessing model.  I will discuss these results and give some initial ideas about what new picture of AGN central engines may emerge. I will also touch upon just-completed or upcoming campaigns on three more AGN (NGC 4593, Mrk 509 and Mrk 110) and more generally on the critical role that LCO is playing in this research.

This work is dedicated to Neil Gehrels, the recently deceased director of Swift, without whose support this experiment would have never been possible.

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