An in-depth spectroscopic examination of molecular bands   from 3D hydrodynamical model atmospheres

Gallagher, A. J.; Caffau, E.; Bonifacio, P.; Ludwig, H.‐G.; Steffen, M.; Homeier, D.; Plez, B.

doi:10.1051/0004-6361/201630272

Cited by 23 publications

(19 citation statements)

References 18 publications

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“…Molecular features are highly susceptible to 3D effects, with abundance corrections becoming more negative towards lower [Fe/H] that are of the right order of magnitude (0.7 to 1.1 dex) to bring their results into agreement with ours (e.g. Collet et al 2006;Gallagher et al 2017).…”

Section: Discussionsupporting

confidence: 78%

Carbon and oxygen in metal-poor halo stars

Amarsi

Nissen

Asplund

et al. 2019

A&A

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Carbon and oxygen are key tracers of the Galactic chemical evolution; in particular, a reported upturn in [C/O] towards decreasing [O/H] in metal-poor halo stars could be a signature of nucleosynthesis by massive Population III stars. We reanalyse carbon, oxygen, and iron abundances in 39 metal-poor turn-off stars. For the first time, we take into account 3D hydrodynamic effects together with departures from local thermodynamic equilibrium (LTE) when determining both the stellar parameters and the elemental abundances, by deriving effective temperatures from 3D non-LTE Hβ profiles, surface gravities from Gaia parallaxes, iron abundances from 3D LTE Fe ii equivalent widths, and carbon and oxygen abundances from 3D non-LTE C i and O i equivalent widths. We find that [C/Fe] stays flat with [Fe/H], whereas [O/Fe] increases linearly up to 0.75 dex with decreasing [Fe/H] down to −3.0 dex. Therefore [C/O] monotonically decreases towards decreasing [O/H], in contrast to previous findings, mainly because the non-LTE effects for O i at low [Fe/H] are weaker with our improved calculations.

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Section: Discussionsupporting

confidence: 78%

Carbon and oxygen in metal-poor halo stars

Amarsi

Nissen

Asplund

et al. 2019

A&A

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“…It should also be noted that many improvements regarding the details of abundance analyses (e.g., NLTE, 3D calculations) have been made in the last few years (Gallagher et al 2017;Nordlander et al 2017). However, these are not yet available for many stars, and whatever has been collected from the literature has likely not (yet) benefited from these advances.…”

Section: Guide For Choosing Element Abundance Samples For Model Compamentioning

confidence: 99%

JINAbase—A Database for Chemical Abundances of Metal-poor Stars

Abohalima

Frebel

2018

ApJS

143

115

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Reconstructing the chemical evolution of the Milky Way is crucial for understanding the formation of stars, planets, and galaxies throughout cosmic time. Different studies associated with element production in the early universe and how elements are incorporated into gas and stars are necessary to piece together how the elements evolved. These include establishing chemical abundance trends, as set by metal-poor stars, comparing nucleosynthesis yield predictions with stellar abundance data, and theoretical modeling of chemical evolution. To aid these studies, we have collected chemical abundance measurements and other information such as stellar parameters, coordinates, magnitudes, and radial velocities, for extremely metal-poor stars from the literature. The database, JINAbase, contains 1658 unique stars, 60% of which have [Fe/H] −2.5. This information is stored in an SQL database, together with a user-friendly queryable web application a) . Objects with unique chemical element signatures (e.g., r-process stars, s-process and CEMP stars) are labeled or can be classified as such. The web application enables fast selection of customized comparison samples from the literature for the aforementioned studies and many more. Using the multiple entries for three of the most well studied metal-poor stars, we evaluate systematic uncertainties of chemical abundances measurements. We provide a brief guide on the selection of chemical elements for model comparisons for nonspectroscopists who wish to learn about metal-poor stars and the details of chemical abundances measurements.

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“…The 3D correction has been computed by Asplund & García Pérez (2001) and González Hernández et al (2010) with two different grids of 3D models and their results are in good agreement. For dwarfs and The star BD +44 • 493 is peculiar, it is very C-rich and Gallagher et al (2017) have shown that the carbon abundance affects the molecular equilibria in 3D hydrodynamical models in a much more prominent way than happens in 1D models. Using a C-rich hydrodynamical model atmosphere computed with the CO 5 BOLD code (Freytag et al 2012), we determined that the 3D correction in this case is only -0.3 dex.…”

Section: Be-o Correlationmentioning

confidence: 99%

Be and O in the ultra metal-poor dwarf 2MASS J18082002-5104378: the Be–O correlation

Spite

Bonifacio

Spite

et al. 2019

A&A

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Context. Measurable amounts of Be could have been synthesised primordially if the Universe were non-homogeneous or in the presence of late decaying relic particles. Aims. We investigate the Be abundance in the extremely metal-poor star 2MASS J1808-5104 ([Fe/H]=-3.84) with the aim of constraining inhomogeneities or the presence of late decaying particles. Methods. High resolution, high signal-to-noise ratio UV spectra were acquired at ESO with the Kueyen 8.2 m telescope and the UVES spectrograph. Abundances were derived using several model atmospheres and spectral synthesis code. Results. We measured log(Be/H) = −14.3 from a spectrum synthesis of the region of the Be line. Using a conservative approach, however we adopted an upper limit two times higher, i.e. log(Be/H) < −14.0. We measured the O abundance from UV OH lines and find [O/H]=-3.46 after a 3D correction. Conclusions. Our observation reinforces the existing upper limit on primordial Be. There is no observational indication for a primordial production of 9 Be. This places strong constraints on the properties of putative relic particles. This result also supports the hypothesis of a homogeneous Universe, at the time of nucleosynthesis. Surprisingly, our upper limit of the Be abundance is well below the Be measurements in stars of similar [O/H]. This may be evidence that the Be-O relation breaks down in the early Galaxy, perhaps due to the escape of spallation products from the gas clouds in which stars such as 2MASS J1808-5104 have formed.

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An in-depth spectroscopic examination of molecular bands from 3D hydrodynamical model atmospheres

Cited by 23 publications

References 18 publications

Carbon and oxygen in metal-poor halo stars

Carbon and oxygen in metal-poor halo stars

JINAbase—A Database for Chemical Abundances of Metal-poor Stars

Be and O in the ultra metal-poor dwarf 2MASS J18082002-5104378: the Be–O correlation

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