CORDIS - Forschungsergebnisse der EU

ASTERoseismic Investigations with SONG and Kepler

Final Report Summary - ASTERISK (ASTERoseismic Investigations with SONG and Kepler)

The prime focus of the present project was to improve our understanding of stellar evolution. This was done by combining advanced observations of stellar oscillations with state-of-the-art modelling of stars. This work has to a large extent been based on very extensive and precise data on stellar oscillations from the NASA Kepler mission which was launched in March 2009. Since the start of this project we have complemented our observational efforts by sophisticated modelling of stellar evolution, and by the development of so-called asteroseismic tools to use the observations to probe stellar interiors. This has involved further development for the accurate computation of stellar models and their oscillation frequencies, and theoretical developments better to understand the relation between the observed frequencies and other aspects of the oscillations and the results of the modelling. This has resulted in measurements of stellar internal rotation and reliable determination of stellar ages, and hence ages of other astrophysical objects. We have also used asteroseismology to characterize central stars in extra-solar planetary systems, determining the size and age of the star and hence constrain the evolution of the planetary systems. A key aspect is the determination of the inclination of the stellar rotation axis relative to the plane of the planetary system, which holds important information about the formation and evolution of planetary systems. The Kepler data have been analysed in a large international collaboration coordinated by our group. We have organized the international use of Kepler and TESS data via our research structures KASC/KASOC and TASC/TASOC and we plan the future access to PLATO (2025, ESA) and E-ELT (2024, ESO). We also assess possible future use of nanosatellites (in collaboration with the industry).

Although space photometry has provided outstanding data for asteroseismology, radial-velocity observations of solar-like pulsators have a huge advantage over space photometry in terms of the ratio between the stellar oscillation signal and background ‘noise’. Thus the ultimate potential for asteroseismology lies in radial-velocity observations of carefully selected bright and nearby stars, with the added advantage that the stars can be very well characterized by other observational techniques. This is the goal of the Stellar Observations Network Group (SONG) whose first telescope, the Hertzsprung SONG Telescope on Tenerife, entered operations in 2014. This has provided unique data on oscillations of several stars, which are now being analysed, and in addition has provided large sets of observations of specific targets addressing a range of scientific goals.