Upcoming seminars
April 23, 2025 at 10:30 AM
Data driven exoplanet detection methods
Nikol Škvařilová
(Brno University of Technology, Faculty of Information Technologies)
The aim of this work is to design and implement an approach for analysing data from the transit method for exoplanet detection. The data comes from the Kepler and TESS space telescopes in the form of light curves, which record the observed brightness of a star over time. In this work, I focused on data-driven modelling and detection of exoplanets using Gaussian process regression. Both non-periodic and periodic kernel models were used to identify light curves suitable for detrending and to remove unwanted trends. Following this, models with periodic kernels were used to investigate the periodicity of the data. Finally, models with non-periodic kernels, trained on folded transits, were applied to detect transits in other light curves by correlation. The approaches described in this thesis provide an automated way to pre-process the data and identify possible transits.
Held seminars in 2024
April 1, 2025 at 13:00 PM
Observational evidence of a potential link between the short-term magnetic activity cycle and planet engulfment
Ján Šubjak
(ASU AV ČR)
The recent discovery of an increasing number of F-type stars displaying short-term magnetic cycles has sparked interest in understanding the cause behind this phenomenon. One hypothesis suggests that planet engulfment could be a potential explanation. A newly found mini-Neptune from the TESS space mission, TOI-2458 b, has been observed in a polar orbit around one of these stars. This finding not only supports the idea of planet engulfment but also indicates that the polar orientation of the planet could provide evidence that a hot Jupiter may have formed in situ. Additionally, our analysis suggests that the population of F-type stars with short magnetic cycles shows deviations within the framework of gyrochronology, further strengthening the case for the planet engulfment hypothesis.
February 4, 2025 at 10:30 AM
Probing the magnetospheres of chemically peculiar stars through the dips in their light curves
Zdeněk Mikulášek
(ÚTFA PřF MU Brno)
The advent of extensive photometric surveys such as Kepler or TESS missions has enabled the recent unexpected unveiling of short-term dips in the phase light curves of the majority of magnetic chemically peculiar stars of the upper main sequence. We explain this characteristic type of stellar variability caused by repeating transits of semi-transparent structures of stellar plasma trapped in the corotating magnetospheres of stars with a global magnetic field. In the light curves of such stars, we detect dips with a typical depth from fractions of mmag to several mmag, the configuration of which is persistent in the scale of decades. The occurrence of photometric dips, frequency, and prominence in the light curves of rotationally modulated objects allows us to judge magnetospheres’ dimension and strength, making this analysis a universally available instrument for diagnosing stellar magnetic fields. We will demonstrate dip analysis on notorious mCP stars such as V901 Ori, CU Vir, V545 Lyr, 56 Ari, or EE Dra.