Data: 09.04.2024

Marzena Sniegowska (Tel Aviv Univ.)

The challenges of the modelling Changing Look Active Galactic Nuclei and nuclear transients phenomena

Streszczenie:
Apart from regular, low-level stochastic variability, some AGNs occasionally show exceptionally large changes in luminosity, spectral shape, and/or X-ray absorption that occur on surprisingly short timescales (even several weeks). The most notable are the changes of the spectral type when the source classified as a Seyfert 1 becomes a Seyfert 2 galaxy or vice versa. Thus a name was coined as 'Changing-Look AGN' (CL AGN). The origin of this phenomenon is still unknown, but for most of the sources, there are strong arguments in favor of intrinsic changes. Understanding the nature of such rapid changes is a challenge to the models of black hole accretion flows since the timescales of the changes are much shorter than the standard disk viscous timescale, related to changes in angular momentum distribution. I will present recent results regarding the model of the time-dependent evolution of a black hole accretion disk unstable due to the dominant radiation pressure as the CL AGN phenomenon scenario. I will discuss also poorly understood flaring AGN with broad Bowen fluorescence emission features, driven by extreme UV radiation that appears within weeks but lasts for well over a year. Those events observationally differ from the tidal disruption events known to date, however, the physics behind them may be interlinked.

Bio:

Bachelor Thesis at the University of Warsaw in 2016 (advisor prof. Lukasz Wyrzykowski). Master Thesis at the University of Warsaw in 2018 (advisor prof. Szymon Kozlowski). PhD CAMK, Warsaw (supervisor prof. Bozena Czerny). Currently (2024): postdoc at the Tel Aviv University in the group of prof. Benny Trakhtenbrot.