WhoSGlAd : A precise characterisation of the Kepler Legacy sample

The increasing number of spaceborne missions provides us with a wealth of exquisite data. Such data combined we the new techniques that are developed then provide us with a deeper understanding of stellar structure and evolution but also shed light on the uncertainties of the current stellar models (e.g. angular momentum transport mechanisms, extent of mixed regions, chemical composition,...). Asteroseimology is one of those techniques. It links stellar pulsation frequencies to the stellar structure and allows the probing of stellar interiors. In particular, the observation of acoustic glitches, which consist in oscillating features in spectra and are caused by sharp variations of the stellar structure, provides very stringent information. Namely, they inform us on the localisation of the transition between a radiative and a convective region or the envelope helium abundance. Thus, the analysis of the glitches signal allows us to provide constraints on several model uncertainties.
25We present here a new method to analyse the oscillation spectra of solar-like pulsators as a whole, i.e. both the acoustic glitches and the slowly varying trend (smooth component) are treated simultaneously. The method, WhoSGlAd (Farnir et al. 2019), takes advantage of linear algebra to compute seismic indicators that are as uncorrelated as possible. Namely, the glitches indicators are completely independent of those of the smoothcomponent. Moreover, the indicators we build are more precise than the ‘usual’ ones which are defined as a function of the radial order. Therefore, it allows to put more stringent constraints on the stellar structure. As an example, we may retrieve an estimation of the surface helium abundance (inaccessible by other means) or obtain constrains on the necessary amount of core overshooting to reproduce observations. Those are more accurate than what we may derive from ‘classical’ means. Such precise measurements are necessary to lift model uncertainties (such as the mass –helium degeneracy observed by Lebreton & Goupil 2014). After showing the advantages and necessity of the method, we will present the application of the method to most stars of the Kepler LEGACY sample (Lund et al. 2017) via the use of the AIMS algorithm. This will enable us to draw trends in the surface helium abundance as well as necessary amount of core overshooting for solar-like pulsators.