Uncertainties in the solar photospheric oxygen abundance

Armas, Melania Cubas; Ramos, A. Asensio; Socas‐Navarro, H.

doi:10.1051/0004-6361/201629446

Cited by 6 publications

(5 citation statements)

References 31 publications

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“…In summary, our currently recommended value for the oxygen abundance based on the results of this work is that from the hierarchical model in which both granules and lanes are considered together, which gives log( O ) = 8.80 ± 0.03. This value is compatible with the results obtained by Grevesse & Sauval (1998) and the results that we achieved in a previous work (see Cubas Armas et al 2017). Therefore, we infer an oxygen abundance comparable with the old high-Z abundances (see e.g., Grevesse & Sauval 1998).…”

Section: Hierarchical Partial Pooling Modelsupporting

confidence: 93%

“…Cubas Armas et al 2017). Therefore, we infer an oxygen abundance comparable with the old high-Z abundances (see e.g., Grevesse & Sauval 1998).…”

Section: Hierarchical Partial Pooling Modelsupporting

confidence: 58%

“…Random errors arising from uncertainties in the observations, the atomic parameters, radiative transfer, and calibration (especially wavelength grid and continuum level) are relatively straightforward to estimate. A full Bayesian treatment of these errors was provided in Cubas Armas et al (2017). However, the most important challenge is in finding a way to estimate the systematic errors, particularly those introduced by the (prescribed) atmosphere.…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Spatially resolved measurements of the solar photospheric oxygen abundance

Armas

Ramos

Socas‐Navarro

2020

A&A

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Aims. We report the results of a novel determination of the solar oxygen abundance using spatially resolved observations and inversions. We seek to derive the photospheric solar oxygen abundance with a method that is robust against uncertainties in the model atmosphere. Methods. We use observations with spatial resolution obtained at the Vacuum Tower Telescope to derive the oxygen abundance at 40 different spatial positions in granules and intergranular lanes. We first obtain a model for each location by inverting the Fe I lines with the NICOLE inversion code. These models are then integrated into a hierarchical Bayesian model that is used to infer the most probable value for the oxygen abundance that is compatible with all the observations. The abundance is derived from the [O I] forbidden line at 6300 Å taking into consideration all possible nuisance parameters that can affect the abundance. Results. Our results show good agreement in the inferred oxygen abundance for all the pixels analyzed, demonstrating the robustness of the analysis against possible systematic errors in the model. We find a slightly higher oxygen abundance in granules than in intergranular lanes when treated separately (log(ϵO) = 8.83 ± 0.02 vs. log(ϵO) = 8.76 ± 0.02), which is a difference of approximately 2-σ. This tension suggests that some systematic errors in the model or the radiative transfer still exist but are small. When taking all pixels together, we obtain an oxygen abundance of log(ϵO) = 8.80 ± 0.03, which is compatible with both granules and lanes within 1-σ. The spread of results is due to both systematic and random errors.

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Section: Hierarchical Partial Pooling Modelsupporting

confidence: 93%

“…Cubas Armas et al 2017). Therefore, we infer an oxygen abundance comparable with the old high-Z abundances (see e.g., Grevesse & Sauval 1998).…”

Section: Hierarchical Partial Pooling Modelsupporting

confidence: 58%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Spatially resolved measurements of the solar photospheric oxygen abundance

Armas

Ramos

Socas‐Navarro

2020

A&A

Self Cite

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“…An extension to using a 1D semi-empirical model atmosphere has recently been presented by Cubas Armas et al (2017Armas et al ( , 2020, who derived a 3D solar model from the spectral inversion of three spatially resolved Fe i lines. They have applied it to the [O i] 630.0 nm line in the Sun to infer log O = 8.80 ± 0.03.…”

Section: Carbon Nitrogen and Oxygenmentioning

confidence: 99%

The chemical make-up of the Sun: A 2020 vision

Asplund,

Amarsi,

Grevesse

2021

Preprint

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Context. The chemical composition of the Sun is a fundamental yardstick in astronomy, relative to which essentially all cosmic objects are referenced. As such, having an accurate knowledge of the solar elemental abundances is crucial for an extremely broad range of topics. Aims. We reassess the solar abundances of all 83 long-lived elements, using highly realistic solar modelling and state-of-the-art spectroscopic analysis techniques coupled with the best available atomic data and observations. Methods. The basis for our solar spectroscopic analysis is a 3D radiative-hydrodynamical model of the solar surface convection and atmosphere, which reproduces the full arsenal of key observational diagnostics. New complete and comprehensive 3-dimensional (3D) spectral line formation calculations taking into account of departures from local thermodynamic equilibrium (non-LTE) are presented for Na, Mg, K, Ca, and Fe using comprehensive model atoms with reliable radiative and collisional data. Our newly derived abundances for C, N, and O are based on a 3D non-LTE analysis of permitted and forbidden atomic lines as well as 3D LTE calculations for in total 879 molecular transitions of CH, C 2 , CO, NH, CN, and OH. Previous 3D-based calculations for another 50 elements are re-evaluated based on updated atomic data, stringent selection of lines, improved consideration of blends, and new non-LTE calculations available in the literature. For elements where spectroscopic determinations of the quiet Sun are not possible the recommended solar abundances are revisited based on complementary methods, including helioseismology (He), solar wind data from the Genesis sample return mission (noble gases), sunspot observations (four elements) and measurements of the most primitive meteorites (15 elements). Results. Our new improved analysis confirms the relatively low solar abundances of C, N, and O obtained in our previous 3Dbased studies: log C = 8.46 ± 0.04, log N = 7.83 ± 0.07, and log O = 8.69 ± 0.04. Excellent agreement between all available atomic and molecular indicators is achieved for C and O, but for N the atomic lines imply a lower abundance than for the molecular transitions for unknown reasons. The revised solar abundances for the other elements also typically agree well with our previously recommended values with just Li, F, Ne, Mg, Cl, Kr, Rb, Rh, Ba, W, Ir, and Pb differing by more than 0.05 dex. The here advocated present-day photospheric metal mass fraction is only slightly higher than our previous value, mainly due to the revised Ne abundance from Genesis solar wind measurements: X surface = 0.7438 ± 0.0054, Y surface = 0.2423 ± 0.0054, Z surface = 0.0139 ± 0.0006, and Z surface /X surface = 0.0187 ± 0.0009. Overall the solar abundances agree well with those of CI chondritic meteorites but we identify a correlation with condensation temperature such that moderately volatile elements are enhanced by ≈ 0.04 dex in the CI chondrites and refractory elements possibly depleted by ≈ 0.02 dex, conflicting with conventional wisdom...

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The chemical make-up of the Sun: A 2020 vision

Asplund

Amarsi

Grevesse

2021

A&A

330

270

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Context. The chemical composition of the Sun is a fundamental yardstick in astronomy, relative to which essentially all cosmic objects are referenced. As such, having accurate knowledge of the solar elemental abundances is crucial for an extremely broad range of topics. Aims. We reassess the solar abundances of all 83 long-lived elements, using highly realistic solar modelling and state-of-the-art spectroscopic analysis techniques coupled with the best available atomic data and observations. Methods. The basis for our solar spectroscopic analysis is a three-dimensional (3D) radiative-hydrodynamical model of the solar surface convection and atmosphere, which reproduces the full arsenal of key observational diagnostics. New complete and comprehensive 3D spectral line formation calculations taking into account of departures from local thermodynamic equilibrium (non-LTE) are presented for Na, Mg, K, Ca, and Fe using comprehensive model atoms with reliable radiative and collisional data. Our newly derived abundances for C, N, and O are based on a 3D non-LTE analysis of permitted and forbidden atomic lines as well as 3D LTE calculations for a total of 879 molecular transitions of CH, C2, CO, NH, CN, and OH. Previous 3D-based calculations for another 50 elements are re-evaluated based on updated atomic data, a stringent selection of lines, improved consideration of blends, and new non-LTE calculations available in the literature. For elements where spectroscopic determinations of the quiet Sun are not possible, the recommended solar abundances are revisited based on complementary methods, including helioseismology (He), solar wind data from the Genesis sample return mission (noble gases), sunspot observations (four elements), and measurements of the most primitive meteorites (15 elements). Results. Our new improved analysis confirms the relatively low solar abundances of C, N, and O obtained in our previous 3D-based studies: log ϵC = 8.46 ± 0.04, log ϵN = 7.83 ± 0.07, and log ϵO = 8.69 ± 0.04. Excellent agreement between all available atomic and molecular indicators is achieved for C and O, but for N the atomic lines imply a lower abundance than for the molecular transitions for unknown reasons. The revised solar abundances for the other elements also typically agree well with our previously recommended values, with only Li, F, Ne, Mg, Cl, Kr, Rb, Rh, Ba, W, Ir, and Pb differing by more than 0.05 dex. The here-advocated present-day photospheric metal mass fraction is only slightly higher than our previous value, mainly due to the revised Ne abundance from Genesis solar wind measurements: Xsurface = 0.7438 ± 0.0054, Ysurface = 0.2423 ± 0.0054, Zsurface = 0.0139 ± 0.0006, and Zsurface/Xsurface = 0.0187 ± 0.0009. Overall, the solar abundances agree well with those of CI chondritic meteorites, but we identify a correlation with condensation temperature such that moderately volatile elements are enhanced by ≈0.04 dex in the CI chondrites and refractory elements possibly depleted by ≈0.02 dex, conflicting with conventional wisdom of the past half-century. Instead, the solar chemical composition more closely resembles that of the fine-grained matrix of CM chondrites with the expected exception of the highly volatile elements. Conclusions. Updated present-day solar photospheric and proto-solar abundances are presented for 83 elements, including for all long-lived isotopes. The so-called solar modelling problem – a persistent discrepancy between helioseismology and solar interior models constructed with a low solar metallicity similar to that advocated here – remains intact with our revised solar abundances, suggesting shortcomings with the computed opacities and/or treatment of mixing below the convection zone in existing standard solar models. The uncovered trend between the solar and CI chondritic abundances with condensation temperature is not yet understood but is likely imprinted by planet formation, especially since a similar trend of opposite sign is observed between the Sun and solar twins.

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Uncertainties in the solar photospheric oxygen abundance

Cited by 6 publications

References 31 publications

Spatially resolved measurements of the solar photospheric oxygen abundance

Spatially resolved measurements of the solar photospheric oxygen abundance

The chemical make-up of the Sun: A 2020 vision

The chemical make-up of the Sun: A 2020 vision

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