Asteroseismic analyses of the physics red-giant interiors

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The study of stars is of paramount importance in astrophysics: almost all investigations of our Galaxy and other galaxies are done through the observation of starlight. Properties of stars in our Galaxy — their chemical abundances, ages, and dynamics — are used to study its chemical and dynamical evolution. While chemical abundances can be obtained from spectroscopy and dynamical properties can be measured by specialized observations such as those provided by satellites like Gaia, ages are much more complicated, because they are model dependent. Using a cutting-edge technique called asteroseismology, the study of the seismic behavior of stars, and combining both observational and theoretical methods, this project will significantly improve and enhance the basic theory of stellar structure and evolution by clarifying some of the most important physical processes that take place deep within stars. In turn, this will make stellar properties, including age estimates, more precise. The results will also allow better calibration of the relation between stellar ages and the abundance of various elements. The project is enriched by an ambitious outreach program based on public lectures, workshops, and summer internships, three components of a scaffolded approach aimed at increasing participation in STEMS for young students and supporting their transition to college. The plan is supported by, and is part of, the well-established and successful “Yale Pathways to Science” program. The project will focus on evolved stars, subgiants and red giants, the ages of which are vital in studying the chemo-dynamical evolution of the Galaxy. The primary goal is to examine the mixing processes, such as overshoot and turbulent mixing, that affect red giant structures, using the individual asteroseismic frequencies and period spacings of these stars. The first part of the project is a theoretical study of the observable seismic signatures produced by different mixing processes; the second is a seismic study of evolved stars with asteroseismic data from Kepler to examine what are the processes that actually take place in stars.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.