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  • 1
    Online Resource
    Online Resource
    Accuracy and Precision of Industrial Stellar Abundances
    Annual Reviews ; 2019
    In:  Annual Review of Astronomy and Astrophysics Vol. 57, No. 1 ( 2019-08-18), p. 571-616
    Details
    In: Annual Review of Astronomy and Astrophysics, Annual Reviews, Vol. 57, No. 1 ( 2019-08-18), p. 571-616
    Abstract: There has been an incredibly large investment in obtaining high-resolution stellar spectra for determining chemical abundances of stars. This information is crucial to answer fundamental questions in astronomy by constraining the formation and evolution scenarios of the Milky Way as well as the stars and planets residing in it. We have just entered a new era, in which chemical abundances of FGK-type stars are being produced at industrial scales, and in which the observations, reduction, and analysis of the data are automatically performed by machines. Here, we review the latest human efforts to assess the accuracy and precision of such industrial abundances by providing insights into the steps and uncertainties associated with the process of determining stellar abundances. We also provide a description of current and forthcoming spectroscopic surveys, focusing on their reported abundances and uncertainties. This allows us to identify which elements and spectral lines are best and why. Finally, we make a brief selection of main scientific questions the community is aiming to answer with abundances. ▪ Uncertainties in abundances need to be disentangled into random and systematic components. ▪ Precision can be increased by applying differential or data-driven methods based on accurate data. ▪ High-resolution and signal-to-noise spectra provide fundamental data that can be used to calibrate lower-resolution and signal-to-noise spectra of millions of stars. ▪ Different survey calibration strategies must agree on a common set of reference stars to create data products that are consistent. ▪ Data products provided by individual groups must be published using standard formats to ensure straightforward applicability.
    Type of Medium: Online Resource
    ISSN: 0066-4146 , 1545-4282
    URL: Article
    DOI: 10.1146/annurev-astro-091918-104509
    RVK:
    US 1090
    Language: English
    Publisher: Annual Reviews
    Publication Date: 2019
    detail.hit.zdb_id: 2160505-1
    detail.hit.zdb_id: 2010305-0
    SSG: 16,12
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  • 2
    Online Resource
    Online Resource
    Metallicity determination of M dwarfs : Expanded parameter range in metallicity and effective temperature
    EDP Sciences ; 2017
    In:  Astronomy & Astrophysics Vol. 604 ( 2017-8), p. A97-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 604 ( 2017-8), p. A97-
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/201730715
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2017
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 3
    Online Resource
    Online Resource
    Laboratory astrophysics for the interpretation of stellar spectra
    Cambridge University Press (CUP) ; 2019
    In:  Proceedings of the International Astronomical Union Vol. 15, No. S350 ( 2019-04), p. 345-349
    Details
    In: Proceedings of the International Astronomical Union, Cambridge University Press (CUP), Vol. 15, No. S350 ( 2019-04), p. 345-349
    Abstract: High-resolution stellar spectra are important tools for studying the chemical evolution of the Milky Way Galaxy, tracing the origin of chemical elements, and characterizing planetary host stars. Large amounts of data have been accumulating, in particular in the optical and infrared wavelength regions. The observed spectral lines are interpreted using model spectra that are calculated based on transition data for numerous species, in particular neutral and singly ionized atoms. We rely heavily on the continuous activities of laboratory astrophysics groups that produce high-quality experimental and theoretical atomic data for the relevant transitions. We give examples for the precision with which the chemical composition of stars observed by different surveys can be determined, and discuss future needs from laboratory astrophysics.
    Type of Medium: Online Resource
    ISSN: 1743-9213 , 1743-9221
    URL: Article
    DOI: 10.1017/S1743921320000824
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2019
    detail.hit.zdb_id: 2170724-8
    SSG: 16,12
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  • 4
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    Online Resource
    Non-LTE radiative transfer with Turbospectrum
    EDP Sciences ; 2023
    In:  Astronomy & Astrophysics Vol. 669 ( 2023-1), p. A43-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 669 ( 2023-1), p. A43-
    Abstract: Physically realistic models of stellar spectra are needed in a variety of astronomical studies, from the analysis of fundamental stellar parameters, to studies of exoplanets and stellar populations in galaxies. Here we present a new version of the widely used radiative transfer code Turbospectrum, which we update so that it is able to perform spectrum synthesis for lines of multiple chemical elements in non-local thermodynamic equilibrium (NLTE). We use the code in the analysis of metallicites and abundances of the Gaia FGK benchmark stars, using 1D MARCS atmospheric models and the averages of 3D radiation-hydrodynamics simulations of stellar surface convection. We show that the new more physically realistic models offer a better description of the observed data, and we make the program and the associated microphysics data publicly available, including grids of NLTE departure coefficients for H, O, Na, Mg, Si, Ca, Ti, Mn, Fe, Co, Ni, Sr, and Ba.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202243673
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2023
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 5
    Online Resource
    Online Resource
    Libraries of synthetic stellar spectra – or are we building palaces upon sand?
    Cambridge University Press (CUP) ; 2006
    In:  Proceedings of the International Astronomical Union Vol. 2, No. S241 ( 2006-12)
    Details
    In: Proceedings of the International Astronomical Union, Cambridge University Press (CUP), Vol. 2, No. S241 ( 2006-12)
    Type of Medium: Online Resource
    ISSN: 1743-9213 , 1743-9221
    URL: Article
    DOI: 10.1017/S1743921307007429
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2006
    detail.hit.zdb_id: 2170724-8
    SSG: 16,12
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  • 6
    Online Resource
    Online Resource
    The LUMBA UVES stellar parameter pipeline
    EDP Sciences ; 2019
    In:  Astronomy & Astrophysics Vol. 629 ( 2019-09), p. A74-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 629 ( 2019-09), p. A74-
    Abstract: Context. The Gaia -ESO Survey has taken high-quality spectra of a subset of 100 000 stars observed with the Gaia spacecraft. The goal for this subset is to derive chemical abundances for these stars that will complement the astrometric data collected by Gaia . Deriving the chemical abundances requires that the stellar parameters be determined. Aims. We present a pipeline for deriving stellar parameters from spectra observed with the FLAMES-UVES spectrograph in its standard fibre-fed mode centred on 580 nm, as used in the Gaia -ESO Survey. We quantify the performance of the pipeline in terms of systematic offsets and scatter. In doing so, we present a general method for benchmarking stellar parameter determination pipelines. Methods. Assuming a general model of the errors in stellar parameter pipelines, together with a sample of spectra of stars whose stellar parameters are known from fundamental measurements and relations, we use a Markov chain Monte Carlo method to quantitatively test the pipeline. Results. We find that the pipeline provides parameter estimates with systematic errors on effective temperature below 100 K, on surface gravity below 0.1 dex, and on metallicity below 0.05 dex for the main spectral types of star observed in the Gaia -ESO Survey and tested here. The performance on red giants is somewhat lower. Conclusions. The pipeline performs well enough to fulfil its intended purpose within the Gaia -ESO Survey. It is also general enough that it can be put to use on spectra from other surveys or other spectrographs similar to FLAMES-UVES.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/201935937
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2019
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 7
    Online Resource
    Online Resource
    Observational constraints on the origin of the elements : IV. Standard composition of the Sun
    EDP Sciences ; 2022
    In:  Astronomy & Astrophysics Vol. 661 ( 2022-05), p. A140-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 661 ( 2022-05), p. A140-
    Abstract: Context. The chemical composition of the Sun is required in the context of various studies in astrophysics, among them in the calculation of standard solar models (SSMs) used to describe the evolution of the Sun from the pre-main-sequence to its present age. Aims. In this work, we provide a critical re-analysis of the solar chemical abundances and corresponding SSMs. Methods. For the photospheric values, we employed new high-quality solar observational data collected with the IAG facility, state-of-the art non-equilibrium modelling, new oscillator strengths, and different atmospheric models, including the MARCS model, along with averages based on Stagger and CO5BOLD 3D radiation-hydrodynamics simulations of stellar convection. We performed new calculations of oscillator strengths for transitions in O I and N I. For O I, which is a critical element with regard to the interior models, calculations were carried out using several independent methods. We investigated our results in comparison with the previous estimates. Results. We find an unprecedented agreement between the new estimates of transition probabilities, thus supporting our revised solar oxygen abundance value. We also provide new estimates of the noble gas Ne abundance. In addition, we discuss the consistency of our photospheric measurements with meteoritic values, taking into account the systematic and correlated errors. Finally, we provide revised chemical abundances, leading to a new value proposed for the solar photospheric present-day metallicity of Z/X = 0.0225, which we then employed in SSM calculations. We find that the puzzling mismatch between the helioseismic constraints on the solar interior structure and the model can be resolved thanks to this new chemical composition.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202142971
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2022
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 8
    Online Resource
    Online Resource
    Metallicity determination of M dwarfs : High-resolution infrared spectroscopy⋆
    EDP Sciences ; 2016
    In:  Astronomy & Astrophysics Vol. 586 ( 2016-2), p. A100-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 586 ( 2016-2), p. A100-
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/201526602
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2016
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 9
    Online Resource
    Online Resource
    Spectroscopic Binaries Among λ Bootis-type Stars
    Cambridge University Press (CUP) ; 2011
    In:  Proceedings of the International Astronomical Union Vol. 7, No. S282 ( 2011-07), p. 333-334
    Details
    In: Proceedings of the International Astronomical Union, Cambridge University Press (CUP), Vol. 7, No. S282 ( 2011-07), p. 333-334
    Abstract: The small group of λ Bootis stars comprises late B to early F-type stars, with moderate to extreme (up to a factor 100) surface under-abundances of most Fe-peak elements and solar abundances of lighter elements (C, N, O, and S). The main mechanisms responsible for this phenomenon are atmospheric diffusion, meridional mixing, and accretion of material from their surroundings. Especially spectroscopic binary (SB) systems with λ Bootis-type components are very important to investigate the evolutionary status and accretion process in more details. Because also δ Scuti type pulsation was found for several members, it gives the opportunity to use the tools of astroseismology for further investigations. We present the results of our long term efforts of detailed abundance analysis, orbital parameter estimation and photometric time series analysis for five well investigated SB systems.
    Type of Medium: Online Resource
    ISSN: 1743-9213 , 1743-9221
    URL: Article
    DOI: 10.1017/S1743921311027773
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2011
    detail.hit.zdb_id: 2170724-8
    SSG: 16,12
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  • 10
    Online Resource
    Online Resource
    Atomic data for stellar spectroscopy
    Cambridge University Press (CUP) ; 2018
    In:  Proceedings of the International Astronomical Union Vol. 14, No. A30 ( 2018-08), p. 458-462
    Details
    In: Proceedings of the International Astronomical Union, Cambridge University Press (CUP), Vol. 14, No. A30 ( 2018-08), p. 458-462
    Abstract: High-precision spectroscopy of large stellar samples plays a crucial role for several topical issues in astrophysics, such as studying the chemical evolution of the Milky Way Galaxy. Data are accumulating from instruments that obtain high-quality spectra of stars in the ultraviolet, optical and infrared wavelength regions on a routine basis. The interpretation of these spectra is often based on synthetic stellar spectra, either calculated on the fly or taken from a spectral library. One of the most important ingredients of these spectra is a set of high-quality transition data for numerous species, in particular neutral and singly ionized atoms. We rely heavily on the continuous activities of laboratory astrophysics groups that produce and improve the relevant experimental and theoretical atomic data. As an example, we briefly describe the efforts done in the context of the Gaia-ESO Public Spectroscopic Survey to compile and assess the best available data in a standard way, providing a list of recommended lines for analysis of optical spectra of FGK stars. The line data, together with specialised analysis methods, allow different surveys to obtain abundances with typical precisions of ∼0.1 dex on an industrial scale for ∼10 chemical elements. Several elements with urgent need for better atomic data have been identified.
    Type of Medium: Online Resource
    ISSN: 1743-9213 , 1743-9221
    URL: Article
    DOI: 10.1017/S174392131900509X
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2018
    detail.hit.zdb_id: 2170724-8
    SSG: 16,12
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