Now you see them, now you don‘t: the disappearing central engines of changing-look quasars

Changing-look quasars are quasars, deriving their luminosity from gas falling onto supermassive black holes in the centers of distant galaxies, which turn off in less than a decade. They are a new discovery, first observed early last year, and their behavior is astounding because it is a challenge to explain how such massive systems can simply fade in just a few years. There are two scenarios that can explain the dramatic changes between quasar and galaxy-like states. The first is that the quasar, which initially outshone all the stars in its host galaxy, has intrinsically dimmed. Alternatively, a dusty cloud may have moved into our line of sight and blocked our view. The observational tests that distinguish  between these scenarios are often inconclusive leaving the changing-look phenomenon largely unexplained. We have been awarded time on one of the 6.5-meter Magellan telescopes in order to make new observations of 9 changing-look quasars. With the new data, we will find out whether they have turned back on, constraining the duration of the on/off states and telling us whether these quasars are truly off or if they are “flickering.” Additionally, we will be able to distinguish between the intrinsic dimming and dust obscuration scenarios and get a new handle on what causes the changing look of changing-look quasars. This request is to allow the PI to travel to the telescope in Chile, in order to make the observations on the nights of Oct 30 and 31, 2016.