Determining the metallicity of the solar envelope using seismic inversion techniques

• Published in: Monthly notices of the Royal Astronomical Society Vol. 472; no. 1; pp. 751 - 764
• Main Authors: Buldgen, G., Salmon, S. J. A. J., Noels, A., Scuflaire, R., Dupret, M. A., Reese, D. R.
• Format: Journal Article
• Language: English
• Published: Oxford University Press 01.11.2017; Oxford University Press (OUP): Policy P - Oxford Open Option A
• Subjects: Astrophysics; Aérospatiale, astronomie & astrophysique; Physical, chemical, mathematical & earth Sciences; Physics; Physique, chimie, mathématiques & sciences de la terre; Space science, astronomy & astrophysics; Sun: oscillations; Sun: fundamental parameters; Sun: abundances; Sun: interior; Sun: helioseismology
• ISSN: 0035-8711; 1365-2966; 1365-8711; 1365-2966
• DOI: 10.1093/mnras/stx2057

Abstract The solar metallicity issue is a long-lasting problem of astrophysics, impacting multiple fields and still subject to debate and uncertainties. While spectroscopy has mostly been used to determine the solar heavy elements abundance, helioseismologists attempted providing a seismic determination of the metallicity in the solar convective envelope. However, the puzzle remains since two independent groups provided two radically different values for this crucial astrophysical parameter. We aim at providing an independent seismic measurement of the solar metallicity in the convective envelope. Our main goal is to help provide new information to break the current stalemate amongst seismic determinations of the solar heavy element abundance. We start by presenting the kernels, the inversion technique and the target function of the inversion we have developed. We then test our approach in multiple hare-and-hounds exercises to assess its reliability and accuracy. We then apply our technique to solar data using calibrated solar models and determine an interval of seismic measurements for the solar metallicity. We show that our inversion can indeed be used to estimate the solar metallicity thanks to our hare-and-hounds exercises. However, we also show that further dependencies in the physical ingredients of solar models lead to a low accuracy. Nevertheless, using various physical ingredients for our solar models, we determine metallicity values between 0.008 and 0.014.