Diploma Thesis
Luminosity changes in active galactic nuclei on short timescales
Helligkeitsänderungen aktiver galaktischer Kerne auf kurzen Zeitskalen
Hannes Horst
Abstract:
In this diploma thesis we treat the phenomenon of luminosity variations in
active galactic nuclei on surprisingly short timescales. We believe the
underlying mechanism to be similar to a "freak wave" effect in the
circumnuclear accretion disk triggered by a radially strongly varying viscosity.
The basis for this idea is β-viscosity as introduced by Duschl et al. (2000).
The β-model predicts a viscosity which is enhanced in selfgravitating regions
of an accretion disk. As an implementation of a selfgravitating non-stationary
disk model turned out to be - due to fragmentation effects - too extensive, we
emulate the behaviour of β-viscosity in a simplified 2-viscosity-model.
We show that this model indeed produces "freak waves" which we then show to
induce a large magnitude luminosity increase in midinfrared on a short
timescale. Thus freak waves may very well be a source for dramatic
luminosity changes in active galactic nuclei.
Thesis: pdf file (508964 Bytes)
only available in German
