COLLOQUIUM Dan Stern, California Institute of Technology

The Extremes of Quasar Variability:  Black Hole Mergers, Acquisitions, and Foreclosures

Variability is one of the key observational properties of quasars, recognized from their initial discovery in the 1960s. Variability probes of the fueling of their supermassive black hole engines, their physics, evolution, and environment. A new generation of synoptic sky surveys, in combination with the novel data analytics tools, offers unprecedented opportunities to study quasars in the time domain.  I will discuss quasars with extreme light curves, including quasars that likely host merging stellar mass black holes in their accretion disks; quasars that have gone through extreme brightening events, likely associated with the acquisition of stars that are torn apart as they wander too close to the black hole; and quasars that have turned off, or foreclosed, on surprisingly fast timescales.  The business of black holes is booming with existing surveys such as the Zwicky Transient Facility, eROSITA, and WISE -- and will expand yet further with surveys starting in the coming year and decade. 

Talk in presence and via Zoom:

https://uni-hamburg.zoom.us/j/66006535328?pwd=aGkrSjJIYmZjK0VpYlpGL0ZrdHg2UT09