Comprehensive stellar seismic analysis

Abstract

Aims. We develop a method that provides a comprehensive analysis of the oscillation spectra of solar-like pulsators. We define new seismic indicators that should be as uncorrelated and as precise as possible and should hold detailed information about stellar interiors. This is essential to improve the quality of the results obtained from asteroseismology as it will provide better stellar models which in turn can be used to refine inferences made in exoplanetology and galactic archaeology. Methods. The presented method – WhoSGlAd – relies on Gram-Schmidt’s orthogonalisation process. A Euclidean vector sub-space of functions is defined and the oscillation frequencies are projected over an orthonormal basis in a specific order. This allowed us to obtain independent coefficients that we combined to define independent seismic indicators. Results. The developed method has been shown to be stable and to converge efficiently for solar-like pulsators. Thus, detailed and precise inferences can be obtained on the mass, the age, the chemical composition and the undershooting in the interior of the studied stars. However, attention has to be paid when studying the helium glitch as there seems to be a degeneracy between the influence of the helium abundance and that of the heavy elements on the glitch amplitude. As an example, we analyse the 16CygA (HD 186408) oscillation spectrum to provide an illustration of the capabilities of the method.

Progress in Global Helioseismology: A New Light on the Solar Modeling Problem and Its Implications for Solar-Like Stars

“…Improving indicator inversions but also generalizing the use of non-linear inversions can be foreseen as the most promising way to fully exploit the data. However, new approaches to treat the seismic information in forward modelling methods also provide important insights in the limitations of seismic information and define the necessary reference models for seismic inversions (Farnir et al, 2019).…”

“…Consequently, efforts have recently been made to quantify the impact of physical ingredients on the determination of these fundamental parameters. In parallel, the wealth of seismic and non-seismic data led to the development of sophisticated modelling tools (Bazot et al, 2012;Gruberbauer et al, 2012;Rendle et al, 2019) and new analyses techniques (see for example Verma et al, 2014;Roxburgh, 2016;Farnir et al, 2019). Most notably, the advent of space-based photometric data allowed the extension of seismic inversion techniques to other targets than the Sun.…”

“…In our exercise, we computed different sets of models for the 16Cyg binary systems using the same initial conditions, summarized in table 5, but various physical ingredients. These values have been taken from a preliminary modelling of the 16Cyg binary system presented in Farnir et al (2019) 5 . The first set of models is composed of standard models of both stars built using the AGSS09 abundances, the FreeEOS equation of state, the OPAL opacities, following the diffusion formalism of Thoul et al (1994), the classical mixing-length theory of convection and using an Eddington grey atmosphere.…”

“…Namely, the results are only presented for the A component in table 2, second column ofFarnir et al (2019), but the modelling was carried out for both components.6 Buldgen et al (2016b) also investigated the use of the OPAS opacities in their modelling, but this should be done more thoroughly.…”

Relevance of the small frequency separation for asteroseismic stellar age, mass, and radius

“…The recent literature also includes other approaches to define seismic indicators to better constrain stellar parameters (see e.g. Farnir et al 2019).…”