The <i>Gaia</i>-ESO Survey: Spectroscopic-asteroseismic analysis of K2 stars in <i>Gaia</i>-ESO

Worley, C. C.; Jofré, P.; Rendle, B. M.; Miglio, A.; Magrini, L.; Feuillet, Diane; Gavel, A.; Smiljanić, R.; Lind, Karin; Korn, A.; Gilmore, G.; Randich, S.; Hourihane, A.; Gonneau, A.; François, P.; Lewis, Jim; Sacco, G. G.; Bragaglia, A.; Heiter, U.; Feltzing, Sofia; Bensby, T.; Irwin, M. J.; Solares, Eduardo González; Murphy, D. N. A.; Bayo, A.; Sbordone, L.; Zwitter, T.; Lanzafame, A. C.; Walton, N. A.; Zaggia, S.; Alfaro, Emilio J.; Morbidelli, L.; Sousa, S.; Monaco, L.; Carraro, G.; Lardo, C.

doi:10.1051/0004-6361/201936726

Cited by 13 publications

(12 citation statements)

References 107 publications

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“…We derive the stellar parameters for the 52 GES-K2 stars using LOTUS. Our results for log g and T eff as compared to Worley et al (2020) are shown in Figure 9 agree well with the photometric and asteroseismic parameters from Worley et al (2020) within their error bars, however our NLTE parameter derivations agree better for both T eff and, particularly for log g.…”

Section: Ges-k2 Starssupporting

confidence: 78%

“…The average uncertainties reported in Worley et al (2020) for T eff and log g of the GES-K2 stars are ±65 K and ±0.02, respectively. We note that these values are close to our parameter grid resolution.…”

Section: Ges-k2 Starsmentioning

confidence: 91%

“…We also test LOTUS by deriving atmospheric stellar parameters of a sample of Kepler-2 (K2) star sample, which was also observed using a high-resolution UVES spectrograph on the VLT as part of the GES survey. Worley et al (2020) combined the high-resolution spectroscopic observations from UVES, photometry, and precise asteroseismic data from K2 to derive selfconsistent stellar parameters for these stars, which represent a good non-spectroscopic sample to compare our stellar parameters derived with LOTUS to.…”

Section: Ges-k2 Starsmentioning

confidence: 99%

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LOTUS: A (non-)LTE Optimization Tool for Uniform derivation of Stellar atmospheric parameters

Li¹,

Ezzeddine²

2022

Preprint

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Precise fundamental atmospheric stellar parameters and abundance determination of individual elements in stars are important for all stellar population studies. Non-Local Thermodynamic Equilibrium (Non-LTE; hereafter NLTE) models are often important for such high precision, however, can be computationally complex and expensive, which renders the models less utilized in spectroscopic analyses. To alleviate the computational burden of such models, we developed a robust 1D, LTE and NLTE fundamental atmospheric stellar parameter derivation tool, LOTUS, to determine the effective temperature T eff , surface gravity log g, metallicity [Fe/H] and microturbulent velocity v mic for FGK type stars, from equivalent width (EW) measurements of Fe i and Fe ii lines. We utilize a generalized curve of growth method to take into account the EW dependencies of each Fe i and Fe ii line on the corresponding atmospheric stellar parameters. A global differential evolution optimization algorithm is then used to derive the optimized fundamental parameters. Additionally, LOTUS can determine precise uncertainties for each stellar parameter using a Markov Chain Monte Carlo (MCMC) algorithm. We test and apply LOTUS on a sample of benchmark stars, as well as stars with available asteroseismic surface gravities from the K2 survey, and metal-poor stars from R-process Alliance (RPA) survey. We find very good agreement between our NLTE-derived parameters in LOTUS to non-spectroscopic values within T eff = ±30 K and log g = ±0.20 dex for benchmark stars. We provide open access of our code, as well as of the interpolated pre-computed NLTE EW grids available on Github , and documentation with working examples on Readthedocs .

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Section: Ges-k2 Starssupporting

confidence: 78%

Section: Ges-k2 Starsmentioning

confidence: 91%

Section: Ges-k2 Starsmentioning

confidence: 99%

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LOTUS: A (non-)LTE Optimization Tool for Uniform derivation of Stellar atmospheric parameters

Li¹,

Ezzeddine²

2022

Preprint

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“…The Gaia-ESO Public Spectroscopic Survey is designed to obtain high quality and high resolution spectra of some 100 000 Milky Way stars (Gilmore et al 2012;Smiljanic et al 2014;Worley et al 2020). Gaia-ESO observed stars using the medium-resolution spectrograph GIRAFFE (R ∼ 20 000) and the high-resolution spectrograph UVES (R ∼47 000) mounted on the VLT.…”

Section: Comparing Our Effective Temperature With That Provided By Ga...mentioning

confidence: 99%

The value-added catalogue for LAMOST DR8 low-resolution spectra

Wang,

Huang,

Yuan

et al. 2022

Preprint

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We present a value-added catalog containing stellar parameters estimated from 7.10 million lowresolution spectra for 5.16 million unique stars with spectral signal-to-noise ratios (SNRs) higher than 10 obtained by the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) Galactic spectroscopic surveys. The catalog presents values of stellar atmospheric parameters (effective temperature T eff , surface gravity log g, metallicity [Fe/H]/[M/H]), α-element to metal abundance ratio [α/M], carbon and nitrogen to iron abundance ratios [C/Fe] and [N/Fe] and 14 bands' absolute magnitudes deduced from LAMOST spectra using the method of neural network. The spectro-photometric distances of those stars are also provided based on the distance modulus. For stars with spectral SNRs larger than 50, precisions of T eff , log g, [Fe/H], [M/H], [C/Fe], [N/Fe] and [α/M] are 85 K, 0.098 dex, 0.05 dex, 0.05 dex, 0.052 dex, 0.082 dex and 0.027 dex, respectively. The errors of 14 band's absolute magnitudes are 0.16-0.22 mag for stars with spectral SNRs larger than 50. The spectro-photometric distance is accurate to 8.5% for stars with spectral SNRs larger than 50, and is more accurate than geometrical distance for stars with distance larger than 2.0 kpc. Our estimates of [Fe/H] are reliable down to [Fe/H] ∼ −3.5 dex, significantly better than previous results. The catalog provide 26,868 unique very metal poor star candidates ([Fe/H] ≤ −2.0). The catalog would be a valuable data set to study the structure and evolution of the Galaxy, especially the solar-neighbourhood and the outer disc.

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“…Apart from the GBS, several samples of calibrating stars, with accurate masses, have become available thanks to recent advances in asteroseismology (Valentini et al 2016(Valentini et al , 2017Serenelli et al 2017;Pinsonneault et al 2018;Worley et al 2020). Stars in eclipsing binaries are an additional option for use as calibrators.…”

Section: Introductionmentioning

confidence: 99%

Titans metal-poor reference stars. I. Accurate effective temperatures and surface gravities for dwarfs and subgiants from 3D non-LTE H$α$ profiles and Gaia parallaxes

Giribaldi,

da Silva,

Smiljanic

et al. 2021

Preprint

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Context. Several large stellar spectroscopic surveys are producing overwhelming amounts of data that can be used for determining stellar atmospheric parameters and chemical abundances. Nonetheless, the accuracy achieved in the derived astrophysical parameters is still insufficient, mainly because of the paucity of adequate calibrators, particularly in the metal-poor regime ([Fe/H] ≤ −1.0). Aims. Our aim is to increase the number of metal-poor stellar calibrators that have accurate parameters. Here, we introduce the Titans metal-poor reference stars: a sample of 41 dwarf and subgiant stars with accurate, but model-dependent, parameters. Methods. Effective temperatures (T eff ) were derived by fitting observed Hα profiles with synthetic lines computed using threedimensional (3D) hydrodynamic model atmospheres that take into account departures from the local thermodynamic equilibrium (non-LTE effects). Surface gravities (log g) were computed using evolutionary tracks and parallaxes from Gaia early-data release 3. Results. The same methods recover the T eff values of the Gaia benchmark stars, which are mostly based on interferometric measurements, with a 1σ dispersion of ±50 K. We assume this to be the accuracy of the Hα profiles computed from 3D non-LTE models for metal-poor dwarfs and subgiants, although this is likely an upper-bound estimate dominated by the uncertainty of the standard T eff values. We achieved an internal precision typically between 30-40 K, these errors dominated by instrumental effects. The final total uncertainty for the T eff values of the Titans are thus estimated to be of the order of 1%. The typical error for log g is ≤ 0.04 dex. In addition, we identified a few members of Gaia-Enceladus, of Sequoia, and of the Helmi stream in our sample. These stars can pave the way for the accurate chemical characterization of these Galactic substructures. Conclusions. Using the Titans as reference, large stellar surveys will be able to improve the internal calibration of their astrophysical parameters. Ultimately, this sample will help users of data from Gaia and large surveys in reaching their goal of redefining our understanding of stars, stellar systems, and the Milky Way.

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The Gaia-ESO Survey: Spectroscopic-asteroseismic analysis of K2 stars in Gaia-ESO

Cited by 13 publications

References 107 publications

LOTUS: A (non-)LTE Optimization Tool for Uniform derivation of Stellar atmospheric parameters

LOTUS: A (non-)LTE Optimization Tool for Uniform derivation of Stellar atmospheric parameters

The value-added catalogue for LAMOST DR8 low-resolution spectra

Titans metal-poor reference stars. I. Accurate effective temperatures and surface gravities for dwarfs and subgiants from 3D non-LTE H$α$ profiles and Gaia parallaxes

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