The 'Lively Stars' Group at the University of Graz aims to understand the activity and variability of solar-like stars. It uses advanced magnetohydrodynamic and radiative transfer codes, as well as data from a new generation of telescopes, to pinpoint the physical phenomena driving different manifestations of stellar activity, and to distinguish them from the exoplanetary signals.
The recent breakthroughs in the field of stellar magnetic activity have been brought about by observations whose primary goal was not studying stars per se, but discovering and characterizing exoplanets around them. Irrespective of whether stellar brightness is being monitored to characterize exoplanetary transits, radial velocities are being measured or precise stellar positions in the sky are being determined to detect stellar wobble around the star-planet barycenter, all these measurements are affected by manifestations of stellar activity. Such manifestations are both a blessing and a curse: on the one hand, they allow getting invaluable insights into the physics of stars, while on the other hand, they directly interfere with the detection and characterization of exoplanets.
The limiting role of stellar activity for studying exoplanets and their atmospheres became especially apparent over the last couple of years. We are now in possession of instrumentation that has the capacity to identify another Earth or even possible biosignatures in the atmosphere of another planet. Yet despite the sophistication of the instrumentation, stellar activity contaminates and overwhelms subtle signals from planets and their atmospheres.
At the heart of this endeavor are 3D radiative magnetohydrodynamics simulations with the MURaM code and radiative transfer calculations with the MPS-ATLAS code. This combination of codes allows describing the interactions between radiation, matter, and magnetic fields in highly turbulent environments of stellar atmospheres.