Marc-Antoine Dupret, Daniel Roy Reese

Constraining additional mixing processes is a central problem in stellar physics. Indeed, their impact on determined stellar ages is non-negligible and thus strongly affects our studies of stellar evolution, galactic history, and exoplanetary systems. However, the quality of the Kepler data allows us to use new seismic tools to constrain these processes. In this talk, we will show a particularly efficient method for constraining chemical mixing in stellar interiors using custommade structural integrated quantities. These quantities are designed to probe particular regions of the stellar interior and are estimated via the SOLA inversion method (Pijpers and Thompson 1994). They help us determine the values of parameters describing extra mixing processes. Inversions of such quantities have been originally described for the mean density in Reese et al. (2012) and have been extended to the acoustic radius and a first indicator of core conditions in Buldgen et al. (2015). A more efficient indicator for core conditions has now been derived and successfully tested using test cases similar to the 16Cyg binary system (Buldgen et al. in prep.). In this talk, we will show how our technique applies to the system 16Cyg and constrains additional mixing processes using the above structural indicators. Additional indicators and further studies will lead to seismically constrained chemical profiles for stars observed by Kepler, thereby helping us to disentangle the problem of additional mixing processes and ultimately to provide better stellar ages.

Daniel Reese, Marc-Antoine Dupret

In the past few years, the CoRoT and Kepler missions have carried out what is now called the space photometry revolution. This revolution is still ongoing thanks to K2 and will be continued by the Tess and Plato2.0 missions. However, the photometry revolution must also be followed by progress in stellar modelling, in order to lead to more precise and accurate determinations of fundamental stellar parameters such as masses, radii and ages. In this context, the long-lasting problems related to mixing processes in stellar interior is the main obstacle to further improvements of stellar modelling. In this talk, we will apply structural asteroseismic inversion techniques to targets from the Kepler LEGACY sample and analyse how these can help us constrain the fundamental parameters and mixing processes in these stars. Our approach is based on previous studies using the SOLA inversion technique (Pijpers & Thompson 1994) to determine integrated quantities such as the mean density (Reese et al. 2012), the acoustic radius, and core conditions indicators (Buldgen et al. 2015a, Buldgen et al. 2015b), and has already been successfully applied to the 16Cyg binary system (Buldgen et al. 2016, Buldgen et al. in prep). We will show how this technique can be applied to the Kepler LEGACY sample and how new indicators can help us to further constrain the chemical composition profiles of stars as well as provide stringent constraints on stellar ages.