The solar silicon abundance based on 3D non-LTE calculations

Amarsi, A. M.; Asplund, Martin

doi:10.1093/mnras/stw2445

Cited by 70 publications

(49 citation statements)

References 60 publications

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“…For silicon, also an important electron donor in particular for stars slightly hotter than the Sun, statistical-equilibrium calculations by Bergemann et al (2013) and Mashonkina et al (2016) suggest that the differential non-LTE effects are very small for solar-type stars (see also Nissen et al 2017). We also note that Amarsi and Asplund (2017) find small 3D effects in the solar case, using statisticalequilibrium calculations and 3D models.…”

Section: Differential Analysesmentioning

confidence: 54%

High-precision stellar abundances of the elements: methods and applications

Nissen

Gustafsson

2018

Astron Astrophys Rev

101

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Efficient spectrographs at large telescopes have made it possible to obtain high-resolution spectra of stars with high signal-to-noise ratio and advances in model atmosphere analyses have enabled estimates of high-precision differential abundances of the elements from these spectra, i.e. with errors in the range 0.01 -0.03 dex for F, G, and K stars.Methods to determine such high-precision abundances together with precise values of effective temperatures and surface gravities from equivalent widths of spectral lines or by spectrum synthesis techniques are outlined, and effects on abundance determinations from using a 3D non-LTE analysis instead of a classical 1D LTE analysis are considered.The determination of high-precision stellar abundances of the elements have led to the discovery of unexpected phenomena and relations with important bearings on the astrophysics of galaxies, stars, and planets, i.e. i) Existence of discrete stellar populations within each of the main Galactic components (disk, halo, and bulge) providing new constraints on models for the formation of the Milky Way. ii) Differences in the relation between abundances and elemental condensation temperature for the Sun and solar twins suggesting dust-cleansing effects in proto-planetary disks and/or engulfment of planets by stars; iii) Differences in chemical composition between binary star components and between members of open or globular clusters showing that star-and cluster-formation processes are more complicated than previously thought; iv) Tight relations between some abundance ratios and age for solar-like stars providing new constraints on nucleosynthesis and Galactic chemical evolution models as well as the composition of terrestrial exoplanets.We conclude that if stellar abundances with precisions of 0.01 -0.03 dex can be achieved in studies of more distant stars and stars on the giant and supergiant branches, many more interesting future applications, of great relevance to stellar and galaxy evolution, are probable. Hence, in planning abundance surveys, it is important to carefully balance the need for large samples of stars against the spectral resolution and signal-to-noise ratio needed to obtain high-precision abundances. Furthermore, it is an advantage to work differentially on stars with similar atmospheric parameters, because then a simple 1D LTE analysis of stellar spectra may be sufficient. However, when determining high-precision absolute abundances or differential abundance between stars having more widely different parameters, e.g. metal-poor stars compared to the Sun or giants to dwarfs, then 3D non-LTE effects must be taken into account.

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Section: Differential Analysesmentioning

confidence: 54%

High-precision stellar abundances of the elements: methods and applications

Nissen

Gustafsson

2018

Astron Astrophys Rev

101

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“…This code is originally based on the code multi3d (Botnen & Carlsson 1999;Leenaarts & Carlsson 2009), but with our own customisations (e.g. Amarsi et al 2016a,b;Amarsi & Asplund 2017). We provide a brief overview of the code here.…”

Section: Post-processing Line Formation Calculationsmentioning

confidence: 99%

Effective temperature determinations of late-type stars based on 3D non-LTE Balmer line formation

Amarsi

Nordlander

Barklem

et al. 2018

A&A

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Hydrogen Balmer lines are commonly used as spectroscopic effective temperature diagnostics of late-type stars. However, reliable inferences require accurate model spectra, and the absolute accuracy of classical methods that are based on one-dimensional (1D) hydrostatic model atmospheres and local thermodynamic equilibrium (LTE) is still unclear. To investigate this, we carry out 3D non-LTE calculations for the Balmer lines, performed, for the first time, over an extensive grid of 3D hydrodynamic stagger model atmospheres. For Hα, Hβ, and Hγ we find significant 1D non-LTE versus 3D non-LTE differences (3D effects): the outer wings tend to be stronger in 3D models, particularly for Hγ, while the inner wings can be weaker in 3D models, particularly for Hα. For Hα, we also find significant 3D LTE versus 3D non-LTE differences (non-LTE effects): in warmer stars (T eff ≈ 6500 K) the inner wings tend to be weaker in non-LTE models, while at lower effective temperatures (T eff ≈ 4500 K) the inner wings can be stronger in non-LTE models; the non-LTE effects are more severe at lower metallicities. We test our 3D non-LTE models against observations of well-studied benchmark stars. For the Sun, we infer concordant effective temperatures from Hα, Hβ, and Hγ; however the value is too low by around 50 K which could signal residual modelling shortcomings. For other benchmark stars, our 3D non-LTE models generally reproduce the effective temperatures to within 1σ uncertainties. For Hα, the absolute 3D effects and non-LTE effects can separately reach around 100 K, in terms of inferred effective temperatures. For metal-poor turn-off stars, 1D LTE models of Hα can underestimate effective temperatures by around 150 K. Our 3D non-LTE model spectra are publicly available, and can be used for more reliable spectroscopic effective temperature determinations.

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“…comm. ), where the radiative transfer code and model atom were presented in Amarsi & Asplund (2017). The average differential 3D NLTE abundance correction for Si is ≈ −0.001 dex.…”

Section: Differential Elemental Abundancesmentioning

confidence: 99%

Detailed chemical compositions of the wide binary HD 80606/80607: revised stellar properties and constraints on planet formation

Liu

Yong

Asplund

et al. 2018

A&A

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Differences in the elemental abundances of planet-hosting stars in binary systems can give important clues and constraints about planet formation and evolution. In this study we performed a high-precision, differential elemental abundance analysis of a wide binary system, HD 80606/80607, based on high-resolution spectra with high signal-to-noise ratio obtained with Keck/HIRES. HD 80606 is known to host a giant planet with the mass of four Jupiters, but no planet has been detected around HD 80607 so far. We determined stellar parameters as well as abundances for 23 elements for these two stars with extremely high precision. Our main results are that (i) we confirmed that the two components share very similar chemical compositions, but HD 80606 is marginally more metal-rich than HD 80607, with an average difference of +0.013 ± 0.002 dex (σ = 0.009 dex); and (ii) there is no obvious trend between abundance differences and condensation temperature. Assuming that this binary formed from material with the same chemical composition, it is difficult to understand how giant planet formation could produce the present-day photospheric abundances of the elements we measure. We cannot exclude the possibility that HD 80606 might have accreted about 2.5 to 5 M Earth material onto its surface, possibly from a planet destabilised by the known highly eccentric giant.

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The solar silicon abundance based on 3D non-LTE calculations

Cited by 70 publications

References 60 publications

High-precision stellar abundances of the elements: methods and applications

High-precision stellar abundances of the elements: methods and applications

Effective temperature determinations of late-type stars based on 3D non-LTE Balmer line formation

Detailed chemical compositions of the wide binary HD 80606/80607: revised stellar properties and constraints on planet formation

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