Postdoctoral positions in asteroseismology

The projects rely heavily on data from the Kepler/TESS and Gaia space missions, as well as from ground-based spectroscopic surveys characterising stellar surface properties. The assembled time series contain a tremendous amount of information, yet to be exploited jointly. As an overarching aim, the three postdocs will work together with a group of PhD students to extract optimal observables from data of non-radial pulsators assembled by the surveys and exploit them to improve the theory of stellar structure and evolution.

The three projects cover a multitude of concrete aims and tasks to be done, requiring various skills. Candidates wishing to apply for more than one position are requested to express their order of preference.

1.) Gravity-mode asteroseismology of open clusters

The applicant will develop customized methods to extract optimal lightcurves from TESS full-frame images of open clusters, by maximally eliminating instrumental effects in the Fourier domain and by treating crowded fields. Thorough time series analysis will be carried out for all cluster stars to identify and extract signatures of gravity-mode oscillations, rotational modulation and possible binarity. The applicant will perform mode identification and model the identified modes of all pulsators and all binaries per clusters jointly with their Gaia data, featuring the strongest set of constraints on each member’s properties. The pioneering goal is to evaluate current stellar evolution theory and to reveal empirical relations deduced from all observed properties of the cluster stars as new recipes for stellar evolution predictions.

2.) Dynamical asteroseismology of eclipsing binaries and tidal evolution 

The applicant will extract optimally defined observables from the survey data to perform joint modelling of photometric, spectroscopic, and astrometric time series of eclipsing binaries, with the aim to deduce accurate dynamical masses and radii. The latter quantities will be used to deduce the ages of the binaries for two large samples of intermediate- and high-mass stars, from stellar modelling based on the latest evolutionary models of stellar interiors and atmospheres. This will lead to an assessment of the so-called mass discrepancy of binary stars, pulsating and non-pulsating, in terms of their metallicities, evolutionary stages, and orbital characteristics. From the multitude of observational constraints, the theory of binary evolution will then be re-evaluated and improved with the aim to assess the effects of tides on internal rotation and mixing of stars, and of angular momentum of the systems. 

3.) Yield computations calibrated by asteroseismology and the chemical enrichment of galaxies 

The applicant will calibrate internal mixing profiles due to convection, rotation, magnetism, and possible binarity from gravity-mode pulsators in the mass range [3,25] Msun. This will be achieved from asteroseismic modelling based on TESS, Gaia, and spectroscopy data. The asteroseismically calibrated mixing profiles and the resulting He and C core masses during the main sequence (MS) and post-MS evolution will be used to calculate new stellar models up to the remnant phase. The corresponding chemical yield predictions will be computed with tools from the ChETEC INFRA (https://chetec-infra.eu/) EU infrastructure (2021- 2026). These chemical yields will then be used to assess the difference between asteroseismically calibrated yields and those for current models not calibrated by asteroseismology. The final aim is to evaluate how much these differences impact chemical evolution models of the galaxy and Magellanic Clouds.