Title: Now you see them, now you don't: the (dis)appearing central engines of changing-look quasars

Abstract: 

Changing-look quasars are high-luminosity active galactic nuclei where we observe dramatic transitions between "quasar-like" and "galaxy-like" spectral states on timescales of a decade or less.  These objects are a challenge to explain in the context of accretion physics and represent unique opportunities to study quasar unification, variability, lifetimes, and feedback.  To date, 13 changing-look quasars have been identified through a combination of serendipitous discovery and systematic searches of the Sloan Digital Sky Survey (SDSS) and Pan-STARRS.  The Time-Domain Spectroscopic Survey (TDSS) in particular offers a promising way of discovering substantial numbers of changing-look quasars because it will revisit several thousand objects with previous spectra from the SDSS, many of which are selected based on substantial photometric variability.  I will describe the results of initial case studies and discuss what we have learned from a growing sample of these objects as well as the prospects for finding and analyzing them in greater numbers with the TDSS and other surveys.