Wednesday Colloquium


"Modeling radiative accretion disks in general relativity"

Aleksander Sądowski (Harvard, CfA)


"Gauss and the Supermassive Black Holes"

Douglas Heggie (School of Mathematics and Maxwell Institute for Mathematical Sciences, University of Edinburgh)

In Gauss's time, theoretical astronomy was largely celestial mechanics, in which Gauss excelled. A hundred years ago this was the one part of astronomy which was left almost untouched by the spectacular growth of astrophysics, and the two areas went their separate way. But with the discovery of extrasolar planets, celestial mechanics is once again at centre stage. "In this talk I trace the modern history of an old idea in celestial mechanics due to Gauss. It has proved to be a fertile idea, which sheds light on much besides extrasolar planets, including the evolution of nuclear star clusters around supermassive black holes, the death of comets, and even the evolution of the Moon.


"Stochastic Modeling of the Fermi/LAT Gamma-Ray Blazar Variability"

Małgorzata Sobolewska (NCAC, Warsaw)

Properties of the blazar gamma-ray variability have a potential to constrain the location and geometry of the blazar gamma-ray emitting region. However, these properties are still largely unknown, and the origin of the blazar variability remains under debate. We study 13 blazars with the most complete light curves collected during the first 4 years of the Fermi Large Area Telescope sky survey. We model them with stochastic processes characterized with power-law power spectral densities (PSD) with one or two bends. We constrain the model parameters such as characteristic gamma-ray variability time scales and PSD slopes, and discuss the implications of our results for theoretical models of blazar variability.


"Symbiotic stars: challenges to the binary evolution theory"

Joanna Mikołajewska (NCAC, Warsaw)