Dr. Kevin Marshall

Widener University – Dept. of Physics

Title: “Exploring Active Galactic Nuclei Through High Energy Variability”

Abstract: Active galactic nuclei represent one of the most extreme environments in the universe. Harboring a million to billion solar mass black holes at their center, gas is drawn in towards the nucleus, where it is heated to temperatures approaching a million Kelvin. These objects are also extremely variable, in some cases changing brightness by a factor of 100 on timescales of years. This variability is most extreme at short wavelengths, where the emission arises from hot regions near the black hole. Despite decades of monitoring, little remains known about the exact mechanism of variability. Recent monitoring efforts spanning the entire electromagnetic spectrum have allowed new insight into emission mechanisms, and have allowed constraints to be placed on the geometry of the emitting region. In my talk, I will review results from these monitoring efforts, and what the future holds for understanding these extreme objects.