Determining the metallicity of the solar envelope using seismic inversion techniques

TL;DR

This paper develops a seismic inversion method to estimate the solar metallicity in the convective envelope, aiming to resolve discrepancies between spectroscopic and helioseismic measurements, but faces challenges due to model dependencies.

Contribution

The authors introduce a new seismic inversion technique and validate it through tests, providing a range of solar metallicity estimates despite model uncertainties.

Findings

Inversion method can estimate solar metallicity.

Model dependencies limit accuracy.

Estimated metallicity range: 0.008 to 0.014.

Abstract

The solar metallicity issue is a long-lasting problem of astrophysics, impacting multi- ple fields and still subject to debate and uncertainties. While spectroscopy has mostly been used to determine the solar heavy elements abundance, helioseismologists at- tempted providing a seismic determination of the metallicity in the solar convective enveloppe. However, the puzzle remains since two independent groups prodived two radically different values for this crucial astrophysical parameter. We aim at provid- ing an independent seismic measurement of the solar metallicity in the convective enveloppe. 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.