Solar oxygen abundance

Maria Bergemann,Manuel Bautista,Svetlana A Yakovleva,Jorrit Leenaarts,Mats Carlsson,Ansgar Reiners,Ahmad Nemer,Andrey K Belyaev,Richard Hoppe,Lyudmila Mashonkina,Yaroslav V Voronov,Ekaterina Semenova,Monika Ellwarth

doi:10.1093/mnras/stab2160

Abstract

ABSTRACT Motivated by the controversy over the surface metallicity of the Sun, we present a re-analysis of the solar photospheric oxygen (O) abundance. New atomic models of O and Ni are used to perform non-local thermodynamic equilibrium (NLTE) calculations with 1D hydrostatic (MARCS) and 3D hydrodynamical (Stagger and Bifrost) models. The Bifrost 3D MHD simulations are used to quantify the influence of the chromosphere. We compare the 3D NLTE line profiles with new high-resolution, R$\approx 700\, 000$, spatially resolved spectra of the Sun obtained using the IAG FTS instrument. We find that the O i lines at 777 nm yield the abundance of log A(O) = 8.74 ± 0.03 dex, which depends on the choice of the H-impact collisional data and oscillator strengths. The forbidden [O i] line at 630 nm is less model dependent, as it forms nearly in LTE and is only weakly sensitive to convection. However, the oscillator strength for this transition is more uncertain than for the 777 nm lines. Modelled in 3D NLTE with the Ni i blend, the 630 nm line yields an abundance of log A(O) = 8.77 ± 0.05 dex. We compare our results with previous estimates in the literature and draw a conclusion on the most likely value of the solar photospheric O abundance, which we estimate at log A(O) = 8.75 ± 0.03 dex.

Highlights

Oxygen is the most abundant chemical element in the Universe and it is of major relevance in modern astrophysics, across difference fields, including precision stellar physics, extragalactic astronomy, planet formation, and galaxy evolution
Oxygen determines much of the opacity in the solar interior (e.g. Bahcall, Serenelli & Basu 2005; Pinsonneault & Delahaye 2009; Serenelli et al 2009), its abundance is critical to the calculation of Standard Solar Models (SSM), which describe the evolution of the Sun from the pre-main-sequence to
We find that the horizontal resolution of (x, y) = (30, 30) offers a reasonable compromise between the computational expense of 3D non-local thermodynamic equilibrium (NLTE) modelling and the physical realism, leading to a small (∼ 1–2 per cent) systematic error in the line strength compared to that obtained the full geometric setup

Summary

Introduction

Oxygen is (behind H and He) the most abundant chemical element in the Universe and it is of major relevance in modern astrophysics, across difference fields, including precision stellar physics, extragalactic astronomy, planet formation, and galaxy evolution. Bahcall, Serenelli & Basu 2005; Pinsonneault & Delahaye 2009; Serenelli et al 2009), its abundance is critical to the calculation of Standard Solar Models (SSM), which describe the evolution of the Sun from the pre-main-sequence to the present age of 4.5 Gyr. Oxygen is the key element in gasphase spectroscopic diagnostics on extragalactic scales, in particular to infer the metallicities from the H II regions This study focuses on the first problem – the chemical abundance of oxygen in the Sun. Over the past decades, several groups approached this problem from various angles.

Results

Discussion

Conclusion