The 3D non-LTE solar nitrogen abundance from atomic lines

Amarsi, A. M.; Grevesse, N.; Grumer, Jon; Asplund, Martin; Barklem, P. S.; Collet, Remo

doi:10.1051/0004-6361/202037890

Cited by 32 publications

(41 citation statements)

References 69 publications

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“…Model atmospheres. As a default solar model atmosphere, we employed the same 3D hydrodynamic simulation of the solar surface convection computed with the Stagger code (Nordlund & Galsgaard 1995;Stein & Nordlund 1998;Magic et al 2013), as was done in our recent studies of 3D (Amarsi et al 2018a(Amarsi et al , 2019(Amarsi et al , 2020. This is an updated version of the Stagger solar model used in Asplund et al (2009), Scott et al (2015a,b), and Grevesse et al (2015), but the differences in photospheric structure are minor.…”

Section: General Considerations Of the Analysismentioning

confidence: 99%

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

Asplund

Amarsi

Grevesse

2021

A&A

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352

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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Section: General Considerations Of the Analysismentioning

confidence: 99%

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

Asplund

Amarsi

Grevesse

2021

A&A

Self Cite

352

270

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“…For O I, the 3D NLTE abundance corrections (with respect to 1D LTE) are also all negative: the 3D effect and the NLTE effect go in the same direction (Amarsi et al 2016a). For C I, however, the 3D NLTE abundance corrections can be positive: the 3D effect and the NLTE effect can go in opposite directions (Amarsi et al 2019a).…”

Section: D Nlte Abundancesmentioning

confidence: 99%

“…Collisions with H I were treated following AK(Amarsi et al 2019a;Kaulakys 1991), BVM19(Belyaev et al 2019), BBD10(Barklem et al 2010), BYB14(Belyaev et al 2014), BVY17, SH84(Zhang et al 2008), SYB20 (Sitnova et al 2020), YBK18 (Yakovleva et al 2018), YBK19 (Yakovleva et al 2019), BGE19 (Bergemann et al 2019), BV17 (Belyaev & Voronov 2017), BBS12 (Barklem et al 2012), BY17 (Belyaev & Yakovleva 2017), BY18 (Belyaev & Yakovleva 2018), and SH84 (0.1) (Steenbock & Holweger 1984) with a scaling factor of S H = 0.1. SH84 (0.0) (Steenbock & Holweger 1984) and with a scaling factor of S H = 0.0.…”

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confidence: 99%

Mono-enriched stars and Galactic chemical evolution

Hansen

Koch

Mashonkina

et al. 2020

A&A

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A long sought after goal using chemical abundance patterns derived from metal-poor stars is to understand the chemical evolution of the Galaxy and to pin down the nature of the first stars (Pop III). Metal-poor, old, unevolved stars are excellent tracers as they preserve the abundance pattern of the gas from which they were born, and hence they are frequently targeted in chemical tagging studies. Here, we use a sample of 14 metal-poor stars observed with the high-resolution spectrograph called the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) to derive abundances of 32 elements (34 including upper limits). We present well-sampled abundance patterns for all stars obtained using local thermodynamic equilibrium (LTE) radiative transfer codes and one-dimensional (1D) hydrostatic model atmospheres. However, it is currently well-known that the assumptions of 1D and LTE may hide several issues, thereby introducing biases in our interpretation as to the nature of the first stars and the chemical evolution of the Galaxy. Hence, we use non-LTE (NLTE) and correct the abundances using three-dimensional model atmospheres to present a physically more reliable pattern. In order to infer the nature of the first stars, we compare unevolved, cool stars, which have been enriched by a single event (“mono-enriched”), with a set of yield predictions to pin down the mass and energy of the Pop III progenitor. To date, only few bona fide second generation stars that are mono-enriched are known. A simple χ2-fit may bias our inferred mass and energy just as much as the simple 1D LTE abundance pattern, and we therefore carried out our study with an improved fitting technique considering dilution and mixing. Our sample presents Carbon Enhanced Metal-Poor (CEMP) stars, some of which are promising bona fide second generation (mono-enriched) stars. The unevolved, dwarf BD+09_2190 shows a mono-enriched signature which, combined with kinematical data, indicates that it moves in the outer halo and likely has been accreted onto the Milky Way early on. The Pop III progenitor was likely of 25.5 M⊙ and 0.6 foe (0.6 1051 erg) in LTE and 19.2 M⊙ and 1.5 foe in NLTE, respectively. Finally, we explore the predominant donor and formation site of the rapid and slow neutron-capture elements. In BD-10_3742, we find an almost clean r-process trace, as is represented in the star HD20, which is a “metal-poor Sun benchmark” for the r-process, while TYC5481-00786-1 is a promising CEMP-r/-s candidate that may be enriched by an asymptotic giant branch star of an intermediate mass and metallicity.

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“…For instance, LTE is a reasonable approach to model the solar photosphere: it is well-known that a LTE radiative transfer modeling is able to reproduce well the solar spectrum (e.g., Holweger 1967;Kurucz 1991Kurucz , 2005. Nevertheless, even regarding the solar spectrum, an non-LTE approach is mandatory for the analysis of certain spectral lines, being particularly important for accurate determinations of chemical abundances (e.g., see Grevesse et al , 2012Amarsi et al 2020, and references 4.2. Overview on radiative transfer codes for hot stars therein).…”

Section: Elementary Concepts Of Radiative Transfermentioning

confidence: 99%

Probing the weak wind phenomenon in Galactic O-type giants

Almeida

Marcolino

Bouret

et al. 2019

A&A

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Aims. Analyses of Galactic late O dwarfs (O8-O9.5V stars) raised the "weak wind problem": spectroscopic mass-loss rates (Ṁ) are up to two orders of magnitude lower than the theoretical values. We investigated the stellar and wind properties of Galactic late O giants (O8-O9.5III stars). These stars have luminosities log(L /L ) ∼ 5.2, which is the critical value (onset of weak winds) proposed in the literature. Methods. We performed a spectroscopic analysis of nine O8-O9.5III stars in the ultraviolet (UV) and optical regions using the model atmosphere code CMFGEN. Results. Stellar luminosities were adopted using calibrations from the literature. Overall, our model spectral energy distributions agree well with the observed ones considering parallaxes from the latest GAIA data release (DR2). The effective temperature derived from the UV region agrees well with the ones from the optical. As expected, the analysis of the Hertzsprung-Russell (HR) diagram shows that our sample is more evolved than late O dwarfs. From the UV region, we foundṀ ∼ 10 −8 − 10 −9 M yr -1 overall. This is lower by ∼ 0.9 − 2.3 dex than predicted values based on the (global) conservation of energy in the wind. The mass-loss rates predicted from first principles, based on the moving reversing layer theory, agree better with our findings, but it fails to match the spectroscopiċ M for the most luminous OB stars. The region of log(L /L ) ∼ 5.2 is critical for both sets of predictions in comparison with the spectroscopic mass-loss rates. CMFGEN models with the predictedṀ (the former one) fail to reproduce the UV wind lines for all the stars of our sample. We reproduce the observed Hα profiles of four objects with ourṀ derived from the UV. Hence, lowṀ values (weak winds) are favored to fit the observations (UV + optical), but discrepancies between the UV and Hα diagnostics remain for some objects. Conclusions. Our results indicate weak winds beyond the O8-9.5V class, since the region of log(L /L ) ∼ 5.2 is indeed critical to the weak wind phenomenon. Since O8-O9.5III stars are more evolved than O8-9.5V, evolutionary effects do not seem to play a role in the onset of the weak wind phenomenon. These findings support that theṀ (for low luminosity O stars) in use in the majority of modern stellar evolution codes must be severely overestimated up to the end of the H-burning phase. Further investigations must evaluate the consequences of weak winds in terms of physical parameters for massive stars (e.g., angular momentum and CNO surface abundances).

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The 3D non-LTE solar nitrogen abundance from atomic lines

Cited by 32 publications

References 69 publications

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

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

Mono-enriched stars and Galactic chemical evolution

Probing the weak wind phenomenon in Galactic O-type giants

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