Description
Changing-Look AGN (CL-AGN) are AGN which transition between Seyfert types, challenging AGN unification models. The cause of CL-AGN transitions is unknown, but popular theories include tidal disruption events in AGN disks, disk instabilities, transitions between radiatively efficient and inefficient accretion flows. Most CL-AGN have been identified via repeat spectroscopy, making it difficult to determine the duration and magnitude of the CL-AGN transition, challenging efforts to observationally constrain CL-AGN origins. I use synthetic photometry in combination with light curve data to develop a new criterion to photometrically identify CL-AGN transitions based on changes in $g$-band magnitude and $g-r$ color. I find that our criterion recovers a photometric transition in five known CL-AGN over the six-year ZTF survey, including a candidate repeating changing-look event in SDSS J084957.78+274728.9. Using simulated AGN light curves, I estimate the false positive rate among the simulated Seyferts to be <2%, and the rate of similar flares among Type 1 Seyferts is ~1% over six years. Photometric CL-AGN transitions last between 21 and 560 days, with a median duration of 360 days, consistent with the thermal or orbital timescales for AGN disks. I use spectroscopy taken throughout the CL-AGN transition in SDSS J084957.78+274728.9 to further test CL-AGN theories. Finally, I discuss how the timing of CL-AGN transitions can be used for AGN disk demographic studies with LSST.