<i>Gaia</i>FGK benchmark stars: opening the black box of stellar element abundance determination

Jofré, P.; Heiter, U.; Worley, C. C.; Blanco-Cuaresma, S.; Soubiran, C.; Masseron, T.; Hawkins, Keith; Adibekyan, V.; Buder, Sven; Casamiquela, L.; Gilmore, G.; Hourihane, A.; Tabernero, H. M.

doi:10.1051/0004-6361/201629833

Cited by 69 publications

(60 citation statements)

References 82 publications

(112 reference statements)

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“…In particular, during idr5 a lower number of Nodes participated in the analysis of the UVES WG11 spectra, compared to dr4. Most of the Nodes considered in the homogenization of [Fe/H] for idr5 based their derivations on the Equivalent Width (EW) analysis and tend to obtain a slightly higher [Fe/H] than that obtained using spectral synthesis (see Jofré et al (2017) for a discussion of systematic differences between different methods of metal abundance derivation). On the other hand, the [FeI/H] and [FeII/H] abundances recomputed by Nodes after the homogenization of the stellar parameters is much closer to the results of the dr4 release (see Table 8, 0.04±0.06 and 0.08±0.07, respectively).…”

Section: Atmospheric Parametersmentioning

confidence: 99%

The Gaia-ESO Survey: The inner disc, intermediate-age open cluster Pismis 18

Hatzidimitriou

Held

Tognelli

et al. 2019

A&A

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Context. Pismis 18 is a moderately populated, intermediate-age open cluster located within the solar circle at a Galactocentric distance of about seven kpc. Few open clusters have been studied in detail in the inner disc region before the Gaia-ESO Survey. Aims. New data from the Gaia-ESO Survey allowed us to conduct an extended radial velocity membership study as well as spectroscopic metallicity and detailed chemical abundance measurements for this cluster. Methods. Gaia-ESO Survey data for 142 potential members, lying on the upper main sequence and on the red clump, yielded radial velocity measurements, which, together with proper motion measurements from the Gaia Second Data Release (Gaia DR2), were used to determine the systemic velocity of the cluster and membership of individual stars. Photometry from Gaia DR2 was used to re-determine cluster parameters based on high confidence member stars only. Cluster abundance measurements of six radial-velocity member stars with UVES high-resolution spectroscopy are presented for 23 elements. Results. The average radial velocity of 26 high confidence members is −27.5 ± 2.5(std) km s −1 with an average proper motion of pmra = −5.65 ± 0.08 (std) mas yr −1 and pmdec = −2.29 ± 0.11 (std) mas yr −1 . According to the new estimates, based on high confidence members, Pismis 18 has an age of τ = 700 +40 −50 Myr, interstellar reddening of E(B − V) = 0.562 +0.012 −0.026 mag and a de-reddened distance modulus of DM 0 = 11.96 +0.10 −0.24 mag. The median metallicity of the cluster (using the six UVES stars) is [Fe/H]= +0.23 ± 0.05 dex, with [α/Fe]= 0.07 ± 0.13 and a slight enhancement of s-and r-neutron-capture elements. Conclusions. With the present work, we fully characterized the open cluster Pismis 18. We confirmed its present location in the inner disc. We estimated a younger age than the previous literature values and we gave, for the first time, its metallicity and its detailed abundances. Its [α/Fe] and [s-process/Fe], both slightly super-solar, are in agreement with other inner-disc open clusters observed by the Gaia-ESO survey.

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Section: Atmospheric Parametersmentioning

confidence: 99%

The Gaia-ESO Survey: The inner disc, intermediate-age open cluster Pismis 18

Hatzidimitriou

Held

Tognelli

et al. 2019

A&A

Self Cite

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“…Still the abundance determination from spectroscopy relies on theoretical models and their systematic error is probably underestimated A59, page 6 of 19 (Jofre et al 2017), as illustrated by the ongoing debate regarding the solar oxygen abundance (Steffen et al 2015). But the solar abundances have been verified using meteorites (Lodders et al 2009), the elemental abundances of other solar system bodies (Lawler et al 1989;McDonough 1995), as well as helioseismological inference (Basu & Antia 2004).…”

Section: Solar Abundancesmentioning

confidence: 99%

Chempy: A flexible chemical evolution model for abundance fitting

Rybizki

Just

Rix

2017

A&A

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Elemental abundances of stars are the result of the complex enrichment history of their galaxy. Interpretation of observed abundances requires flexible modeling tools to explore and quantify the information about Galactic chemical evolution (GCE) stored in such data. Here we present Chempy, a newly developed code for GCE modeling, representing a parametrized open one-zone model within a Bayesian framework. A Chempy model is specified by a set of five to ten parameters that describe the effective galaxy evolution along with the stellar and star-formation physics: for example, the star-formation history (SFH), the feedback efficiency, the stellar initial mass function (IMF), and the incidence of supernova of type Ia (SN Ia). Unlike established approaches, Chempy can sample the posterior probability distribution in the full model parameter space and test data-model matches for different nucleosynthetic yield sets. It is essentially a chemical evolution fitting tool. We straightforwardly extend Chempy to a multi-zone scheme. As an illustrative application, we show that interesting parameter constraints result from only the ages and elemental abundances of the Sun, Arcturus, and the present-day interstellar medium (ISM). For the first time, we use such information to infer the IMF parameter via GCE modeling, where we properly marginalize over nuisance parameters and account for different yield sets. We find that 11.6 +2.1 −1.6 % of the IMF explodes as core-collapse supernova (CC-SN), compatible with Salpeter (1955, ApJ, 121, 161). We also constrain the incidence of SN Ia per 10 3 M to 0.5−1.4. At the same time, this Chempy application shows persistent discrepancies between predicted and observed abundances for some elements, irrespective of the chosen yield set. These cannot be remedied by any variations of Chempy's parameters and could be an indication of missing nucleosynthetic channels. Chempy could be a powerful tool to confront predictions from stellar nucleosynthesis with far more complex abundance data sets and to refine the physical processes governing the chemical evolution of stellar systems.

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“…The same problem was tackled again even more thoroughly by Jofré et al (2017), who determined four abundances for four Gaia Benchmark Stars (Jofré et al 2014(Jofré et al , 2015Heiter et al 2015b;Hawkins et al 2016) using six different methods and one representative line for each of the four elements with fixed atmospheric parameters (i.e. effective temperature, surface gravity and metallicity).…”

Section: Introductionmentioning

confidence: 99%

Modern stellar spectroscopy caveats

Blanco-Cuaresma

2019

Monthly Notices of the Royal Astronomical Society

245

143

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Multiple codes are available to derive atmospheric parameters and individual chemical abundances from high-resolution spectra of AFGKM stars. Almost all spectroscopists have their own preferences regarding which code and method to use. But the intrinsic differences between codes and methods lead to complex systematics that depend on multiple variables such as the selected spectral regions and the radiative transfer code used. I expand iSpec, a popular open-source spectroscopic tool, to support the most well-known radiative transfer codes and assess their similarities and biases when using multiple set-ups based on the equivalent-width method and the synthetic spectralfitting technique (interpolating from a pre-computed grid of spectra or synthesizing with interpolated model atmospheres). This work shows that systematic differences on atmospheric parameters and abundances between most of the codes can be reduced when using the same method and executing a careful spectral feature selection. However, it may not be possible to ignore the remaining differences, depending on the particular case and the required precision. Regarding methods, equivalent-widthbased and spectrum-fitting analyses exhibit large differences that are caused by their intrinsic differences, which is significant given the popularity of these two methods. The results help to identify the key caveats of modern spectroscopy that all scientists should be aware of before trusting their own results or being tempted to combine atmospheric parameters and abundances from the literature.

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GaiaFGK benchmark stars: opening the black box of stellar element abundance determination

Cited by 69 publications

References 82 publications

The Gaia-ESO Survey: The inner disc, intermediate-age open cluster Pismis 18

The Gaia-ESO Survey: The inner disc, intermediate-age open cluster Pismis 18

Chempy: A flexible chemical evolution model for abundance fitting

Modern stellar spectroscopy caveats

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