Résumé:

The proliferation of wide-field multi-epoch imaging surveys has now opened a new window to the time-domain for discovery of new and rare time-variable phenomena. From these surveys, the recent discovery of changing-look quasars poses potential challenges to our understanding of accretion onto supermassive black holes. In this phenomenon, luminous quasars suddenly fade into quiescent galaxies over timescales of just a few years, a factor of 10000 faster than expected. I will examine different explanations for the origin of changing-look quasars, and discuss their incredible usefulness in probing accretion physics, supermassive black hole feedback, and galaxy evolution over cosmic time.