Asteroseismic grid-modeling of red giants: precise age constraints for galactic-archeology
Precise stellar ages are crucial for understanding the Galaxy’s dynamical and chemical evolution. Stellar evolution and asteroseismic modeling, combined with precise spectroscopic and asteroseismic observables, can significantly reduce age uncertainties. This is particularly evident when adding additional constraints, such as binarity or individual oscillation frequencies, to the modeling. In this talk, I will discuss how different asteroseismic modeling approaches constrain red giant ages, contribute to the reduction of the uncertainties, and affect systematic offsets between methods.
The project builds on a study of a benchmark red-giant binary, in which combining grid-based modeling with binarity, spectroscopy, and asteroseismology yielded an age precision of 9%, a significant improvement over classical single-star global seismic modeling for red-giant stars. Extending this methodology, I developed an individual-frequency grid-modeling pipeline for red giant stars. Applied to approximately 100 Kepler red giants, close to solar mass and metallicity, this approach achieves mean-age uncertainties of 13% across a significant range of galactic ages, representing a factor-of-two improvement over global seismic modeling. Furthermore, the stellar ages derived from individual-frequency modeling are consistently larger than those derived from global seismic modeling. Given fixed input physics in the models, this indicates a systematic offset between methods even in the solar-parameter regime.
This modeling framework is now being extended to Galactic halo stars, targets poor in metals and enriched in alpha elements that are crucial for understanding the Milky Way’s evolution. Determining precise parameters for these populations will place them into a broader context of Galactic formation and chemical history.