MY TEACHING

Asteroseismology of the heartbeat star KIC 5006817
Result of ERASMUS+ summer school 2020
Contributions of the Astronomical Observatory Skalnaté Pleso, vol. 51, no. 1, p. 45-57.
Merc, J.; Kalup, Cs.; Rathour, R. S.; Sánchez Arias, J. P.; Beck, P.

This paper summarizes the project work on asteroseismology at the ERASMUS+ GATE 2020 Summer school on space satellite data. The aim was to do a global asteroseismic analysis of KIC 5006817, and quantify its stellar properties using the high-quality, state of the art space missions data. We employed the aperture photometry to analyze the data from the Kepler space telescope and the Transiting Exoplanet Survey Satellite (TESS). Using the lightkurve Python package, we have derived the asteroseismic parameters and calculated the stellar parameters using the scaling relations. Our analysis of KIC 5006817 confirmed its classification as a heartbeat binary. The rich oscillation spectrum facilitate estimating power excess (νmax) at 145.50±0.50 μHz and large frequency separation (Δν) to be 11.63±0.10 μHz. Our results showed that the primary component is a low-luminosity, red-giant branch star with a mass, radius, surface gravity and luminosity of 1.53±0.07 M⊙, 5.91±0.12 R⊙, 3.08±0.01 dex, and 19.66±0.73 L⊙, respectively. The orbital period of the system is 94.83±0.05 d.

KIC 9163796 - a benchmark binary for age determination
Student Poster contribution
Proceedings of the conference Stars and their Variability Observed from Space, held in Vienna on August 19-23, 2019. Eds.: C. Neiner, W. W. Weiss, D. Baade, R. E. Griffin, C. C. Lovekin, A. F. J. Moffat. University of Vienna, 2020, pp.351-352
Grossmann, D. H.; Beck, P. G.; Hanslmeier, A.

Binary systems constitute a valuable tool in astrophysics for gaining a deeper understanding of stellar evolution and determining stellar ages. That is particularly true for the double-lined binary KIC 9163796, which has a mass ratio of almost unity but varies significantly in temperature, luminosity and Lithium abundance. This paper outlined our approach to generate a combined stellar model for it using the MESA stellar-evolution code. By combining the available observational data with the models we derived, we aimed to find the best-fitting models for both components and to extrapolate the system's age from them.

Testing the asymptotic relation for period spacings from mixed modes of red giants observed with the Kepler mission
Published form of a diploma theses co-supervised by me
Astronomy & Astrophysics, Volume 588, id.A82, 14 pp (2016).
Buysschaert, B.; Beck, P. G.; Corsaro, E.; Christensen-Dalsgaard, J.; Aerts, C.; Arentoft, T.; Kjeldsen, H.; García, R. A.; Silva Aguirre, V.; Degroote, P.

Context. Dipole mixed pulsation modes of consecutive radial order have been detected for thousands of low-mass red-giant stars with the NASA space telescope Kepler. These modes have the potential to reveal information on the physics of the deep stellar interior.
Aims: Different methods have been proposed to derive an observed value for the gravity-mode period spacing, the most prominent one relying on a relation derived from asymptotic pulsation theory applied to the gravity-mode character of the mixed modes. Our aim is to compare results based on this asymptotic relation with those derived from an empirical approach for three pulsating red-giant stars.
Methods: We developed a data-driven method to perform frequency extraction and mode identification. Next, we used the identified dipole mixed modes to determine the gravity-mode period spacing by means of an empirical method and by means of the asymptotic relation. In our methodology we consider the phase offset, ɛg, of the asymptotic relation as a free parameter.
Results: Using the frequencies of the identified dipole mixed modes for each star in the sample, we derived a value for the gravity-mode period spacing using the two different methods. These values differ by less than 5%. The average precision we achieved for the period spacing derived from the asymptotic relation is better than 1%, while that of our data-driven approach is 3%.
Conclusions: Good agreement is found between values for the period spacing derived from the asymptotic relation and from the empirical method. The achieved uncertainties are small, but do not support the ultra-high precision claimed in the literature. The precision from our data-driven method is mostly affected by the differing number of observed dipole mixed modes. For the asymptotic relation, the phase offset, ɛg, remains ill defined, but enables a more robust analysis of both the asymptotic period spacing and the dimensionless coupling factor. However, its estimation might still offer a valuable observational diagnostic for future theoretical modeling.