Francesco L. Villante^1,2, Aldo M. Serenelli³, Franck Delahaye⁴, and Marc H. Pinsonneault⁵

¹Dipartimento di Scienze Fisiche e Chimiche, Università dell’Aquila, I-67100 L’Aquila, Italy
²Istituto Nazionale di Fisica Nucleare (INFN), Laboratori Nazionali del Gran Sasso (LNGS), I-67100 Assergi (AQ), Italy
³Instituto de Ciencias del Espacio (CSIC-IEEC), Facultad de Ciencias, E-08193 Bellaterra, Spain
⁴LERMA, Observatoire de Paris, ENS, UPMC, UCP, CNRS, F-92190 Meudon, France
⁵Astronomy Department, Ohio State University, Columbus, OH 43210, USA

We perform a quantitative analysis of the solar composition problem by using a statistical approach that allows us to combine the information provided by helioseismic and solar neutrino data in an effective way. We include in our analysis the helioseismic determinations of the surface helium abundance and of the depth of the convective envelope, the measurements of the ⁷Be and ⁸B neutrino fluxes, and the sound speed profile inferred from helioseismic frequencies. We provide all the ingredients to describe how these quantities depend on the solar surface composition, different from the initial and internal composition due to the effects of diffusion and nuclear reactions, and to evaluate the (correlated) uncertainties in solar model predictions. We include error sources that are not traditionally considered such as those from inversion of helioseismic data. We, then, apply the proposed approach to infer the chemical composition of the Sun. Our result is that the opacity profile of the Sun is well constrained by the solar observational properties. In the context of a two-parameter analysis in which elements are grouped as volatiles (i.e., C, N, O, and Ne) and refractories (i.e., Mg, Si, S, and Fe), the optimal surface composition is found by increasing the abundance of volatiles by (45 ± 4)% and that of refractories by (19 ± 3)% with respect to the values provided by Asplund et al. (2009, ARA&A, 47, 481). This corresponds to the abundances ε_O = 8.85 ± 0.01 and ε_Fe = 7.52 ± 0.01, which are consistent at the ~1σ level with those provided by Grevesse & Sauval (1998, SSRv, 85, 161). As an additional result of our analysis, we show that the best fit to the observational data is obtained with values of input parameters of the standard solar models (radiative opacities, gravitational settling rate, and the astrophysical factors S₃₄ and S₁₇) that differ at the ~1σ level from those presently adopted.

Reference
Villante FL, Serenelli AM, Delahaye F and Pinsonneault MH (2014) The Chemical Composition of the Sun from Helioseismic and Solar Neutrino Data. The Astrophysical Journal 787:13.
[doi:10.1088/0004-637X/787/1/13]

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