The elemental composition of the Sun

Scott, Pat; Grevesse, N.; Asplund, Martin; Sauval, A. J.; Lind, Karin; Takeda, Yoichi; Collet, Remo; Trampedach, Regner; Hayek, Wolfgang

doi:10.1051/0004-6361/201424109

Cited by 212 publications

(184 citation statements)

References 96 publications

(104 reference statements)

Supporting

Mentioning

167

Contrasting

Order By: Relevance

“…For the Sun, non-LTE effects are very weak, of the order of 0.01 dex, while 3D 1D abundances are higher by 0.05−0.15 dex than the corresponding 1D abundances because of the hotter temperatures (∼1%) in the line-formation region. Only two lines overlap with the recent study by Scott et al (2015), but the average solar abundances nevertheless match well (A(Mg) Scott et. al.…”

Section: Optical Absorption Linessupporting

confidence: 81%

“…Figure 8 compares theoretical spectra for the 7.3, 12.2, and 12.3 μm emission lines with the observed solar spectrum across the solar disk. The synthetic spectral lines are calculated for various model atoms, using the currently accepted solar photospheric Mg abundance (Scott et al 2015), A(Mg) = 7.59, and employing the 3D 1D solar model atmosphere. We note that our modelling does not include pressure-induced line shifts, and other atomic data for such shifts do not exist.…”

Section: Infrared Emission Linesmentioning

confidence: 99%

See 1 more Smart Citation

Mg line formation in late-type stellar atmospheres

Osorio

Barklem

Lind

et al. 2015

A&A

130

View full text Add to dashboard Cite

Context. Magnesium is an element of significant astrophysical importance, often traced in late-type stars using lines of neutral magnesium, which is expected to be subject to departures from local thermodynamic equilibrium (LTE). The importance of Mg, together with the unique range of spectral features in late-type stars probing different parts of the atom, as well as its relative simplicity from an atomic physics point of view, makes it a prime target and test bed for detailed ab initio non-LTE modelling in stellar atmospheres. Previous non-LTE modelling of spectral line formation has, however, been subject to uncertainties due to lack of accurate data for inelastic collisions with electrons and hydrogen atoms. Aims. In this paper we build and test a Mg model atom for spectral line formation in late-type stars with new or recent inelastic collision data and no associated free parameters. We aim to reduce these uncertainties and thereby improve the accuracy of Mg non-LTE modelling in late-type stars.Methods. For the low-lying states of Mg i, electron collision data were calculated using the R-matrix method. Hydrogen collision data, including charge transfer processes, were taken from recent calculations by some of us. Calculations for collisional broadening by neutral hydrogen were also performed where data were missing. These calculations, together with data from the literature, were used to build a model atom. This model was then employed in the context of standard non-LTE modelling in 1D (including average 3D) model atmospheres in a small set of stellar atmosphere models. First, the modelling was tested by comparisons with observed spectra of benchmark stars with well-known parameters. Second, the spectral line behaviour and uncertainties were explored by extensive experiments in which sets of collisional data were changed or removed. Results. The modelled spectra agree well with observed spectra from benchmark stars, showing much better agreement with line profile shapes than with LTE modelling. The line-to-line scatter in the derived abundances shows some improvements compared to LTE (where the cores of strong lines must often be ignored), particularly when coupled with averaged 3D models. The observed Mg emission features at 7 and 12 μm in the spectra of the Sun and Arcturus, which are sensitive to the collision data, are reasonably well reproduced. Charge transfer with H is generally important as a thermalising mechanism in dwarfs, but less so in giants. Excitation due to collisions with H is found to be quite important in both giants and dwarfs. The R-matrix calculations for electron collisions also lead to significant differences compared to when approximate formulas are employed. The modelling predicts non-LTE abundance corrections ΔA(Mg) NLTE−LTE in dwarfs, both solar metallicity and metal-poor, to be very small (of order 0.01 dex), even smaller than found in previous studies. In giants, corrections vary greatly between lines, but can be as large as 0.4 dex. Conclusions. Our results emphasise ...

show abstract

Section: Optical Absorption Linessupporting

confidence: 81%

Section: Infrared Emission Linesmentioning

confidence: 99%

Mg line formation in late-type stellar atmospheres

Osorio

Barklem

Lind

et al. 2015

A&A

130

View full text Add to dashboard Cite

show abstract

“…They concluded that if NLTE effects are taken into account, then the photospheric iron abundance A Fe = 7.50±0.1, in agreement with the meteoritic value given by Grevesse & Sauval (1998). The new generation of 3D HD models of the solar photosphere (see, e.g., Caffau et al 2008;Asplund et al 2009;Pereira et al 2013;Trampedach et al 2013;Scott et al 2015a) have a shallower temperature stratification than the 3D model of Asplund et al (2000a), hence weaker ultraviolet overionization and, as a result, smaller NLTE abundance corrections.…”

Section: Introductionmentioning

confidence: 57%

The impact of surface dynamo magnetic fields on the solar iron abundance

Shchukina

Bueno

2015

A&A

View full text Add to dashboard Cite

Most chemical abundance determinations ignore that the solar photosphere is significantly magnetized by the ubiquitous presence of a small-scale magnetic field. A recent investigation has suggested that there should be a significant impact on the derived iron abundance, owing to the magnetically induced changes on the photospheric temperature and density structure (indirect effect). The three-dimensional (3D) photospheric models used in that investigation have non-zero net magnetic flux values and stem from magnetoconvection simulations without small-scale dynamo action. Here we address the same problem by instead using 3D models of the quiet solar photosphere that result from a state-of-the-art magneto-convection simulation with small-scale dynamo action, where the net magnetic flux is zero. One of these 3D models has negligible magnetization, while the other is characterized by a mean field strength of 160 Gauss in the low photosphere. With such 3D models we carried out spectral synthesis for a large set of Fe i lines to derive abundance corrections, taking the above-mentioned indirect effect and the Zeeman broadening of the intensity profiles (direct effect) into account. We conclude that if the magnetism of the quiet solar photosphere is mainly produced by a small-scale dynamo, then its impact on the determination of the solar iron abundance is negligible.

show abstract

“…The detailed calculations by Lind et al (2012) (Baumüller & Gehren 1996;Shi et al 2008;Scott et al 2015b). This suggests that differential corrections for the Al and Si abundances can be neglected.…”

Section: Non-lte and 3d Effectsmentioning

confidence: 99%

High-precision abundances of elements in solar twin stars

Nissen

2015

A&A

256

304

View full text Add to dashboard Cite

Context. High-precision determinations of abundances of elements in the atmospheres of the Sun and solar twin stars indicate that the Sun has an unusually low ratio between refractory and volatile elements. This has led to the suggestion that the relation between abundance ratios, [X/Fe], and elemental condensation temperature, T C , can be used as a signature of the existence of terrestrial planets around a star. Aims. HARPS spectra with S /N 600 for 21 solar twin stars in the solar neighborhood and the Sun (observed via reflected light from asteroids) are used to determine very precise (σ ∼ 0.01 dex) differential abundances of elements in order to see how well [X/Fe] is correlated with T C and other parameters such as stellar age. Methods. Abundances of C, O, Na, Mg, Al, Si, S, Ca, Ti, Cr, Fe, Ni, Zn, and Y are derived from equivalent widths of weak and medium-strong spectral lines using MARCS model atmospheres with parameters determined from the excitation and ionization balance of Fe lines. Non-LTE effects are considered and taken into account for some of the elements. In addition, precise (σ 0.8 Gyr) stellar ages are obtained by interpolating between Yonsei-Yale isochrones in the log g -T eff diagram. Results. It is confirmed that the ratio between refractory and volatile elements is lower in the Sun than in most of the solar twins (only one star has the same [X/Fe]-T C distribution as the Sun), but for many stars, the relation between [X/Fe] and T C is not well defined.

show abstract

The elemental composition of the Sun

Cited by 212 publications

References 96 publications

Mg line formation in late-type stellar atmospheres

Mg line formation in late-type stellar atmospheres

The impact of surface dynamo magnetic fields on the solar iron abundance

High-precision abundances of elements in solar twin stars

Contact Info

Product

Resources

About