Investigating stellar convective cores with inversions of frequency separation ratios

In the past decades, the advent of space-based photometry missions such as CoRoT, Kepler, and TESS enabled the rapid development of asteroseismology. The field will further grow with the future PLATO mission. In this context, using inversion techniques can offer quasi-model-independent constraints on the stellar properties from a given stellar oscillation spectrum, such as mean density or core properties for example. However, the linear inversion techniques are limited by the so-called surface effects. Therefore, we developed an inversion based on frequency separation ratios instead of individual frequencies to damp their impact and constrain convective cores (Bétrisey & Buldgen 2022).

We verified our inversion technique by conducting tests in a controlled environment and conducted an extensive hare and hounds exercise to test the behavior of our technique in conditions close to an actual application on an observed target.

We found that the inversion is not affected by surface effects. In addition, we also found that with the construction of an extensive set of models, favored and forbidden regions can be highlighted in the parameter space. This inversion based on frequency separation ratios seems promising at probing the properties of convective cores, especially for F-type stars exhibiting solar-like oscillations. In this context, the quasi-model-independent constraints can be used to improve the physical ingredients of the models of such targets, especially the mixing close to the convective boundary.