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After the All-Sky Automated Survey for SuperNovae (ASAS-SN) discovered asignificant brightening of the inner region of NGC 2617, we began a ~70 dayphotometric and spectroscopic monitoring campaign from the X-ray throughnear-infrared (NIR) wavelengths. We report that NGC 2617 went through adramatic outburst, during which its X-ray flux increased by over an order ofmagnitude followed by an increase of its optical/ultraviolet (UV) continuumflux by almost an order of magnitude. NGC 2617, classified as a Seyfert 1.8galaxy in 2003, is now a Seyfert 1 due to the appearance of broad opticalemission lines and a continuum blue bump. Such "changing look Active GalacticNuclei (AGN)" are rare and provide us with important insights about AGNphysics. Based on the Hbeta line width and the radius-luminosity relation, weestimate the mass of central black hole to be (4 +/- 1) x 10^7 M_sun. When wecross-correlate the light curves, we find that the disk emission lags theX-rays, with the lag becoming longer as we move from the UV (2-3 days) to theNIR (6-9 days). Also, the NIR is more heavily temporally smoothed than the UV.This can largely be explained by a simple model of a thermally emitting thindisk around a black hole of the estimated mass that is illuminated by theobserved, variable X-ray fluxes.

The Man Behind the Curtain: X-rays Drive the UV through NIR Variability in the 2013 AGN Outburst in NGC 2617