Fundamental stellar parameters of benchmark stars from CHARA interferometry: I. metal-poor stars
Context. Benchmark stars are crucial as validating standards for current as well as future large stellar surveys of the Milky Way. However, the number of suitable metal-poor benchmark stars is currently limited, owing to the difficulty in determining reliable effective temperatures (<i>T<i/...
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| Main Authors: | , , , , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
04 August 2020
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| In: |
Astronomy and astrophysics
Year: 2020, Volume: 640 |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/202037590 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1051/0004-6361/202037590 Verlag, lizenzpflichtig, Volltext: https://www.aanda.org/articles/aa/abs/2020/08/aa37590-20/aa37590-20.html 
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| Author Notes: | I. Karovicova, T.R. White, T. Nordlander, L. Casagrande, M. Ireland, D. Huber, and P. Jofré |
| Summary: | Context. Benchmark stars are crucial as validating standards for current as well as future large stellar surveys of the Milky Way. However, the number of suitable metal-poor benchmark stars is currently limited, owing to the difficulty in determining reliable effective temperatures (<i>T<i/><sub>eff<sub/>) in this regime. Aims. We aim to construct a new set of metal-poor benchmark stars based on reliable interferometric effective temperature determinations and a homogeneous analysis. The aim is to reach a precision of 1% in <i>T<i/><sub>eff<sub/>, as is crucial for sufficiently accurate determinations of the full set of fundamental parameters and abundances for the survey sources. Methods. We observed ten late-type metal-poor dwarfs and giants: HD 2665, HD 6755, HD 6833, HD 103095, HD 122563, HD 127243, HD 140283, HD 175305, HD 221170, and HD 224930. Only three of them (HD 103095, HD 122563, and HD 140283) have previously been used as benchmark stars. For the observations, we used the high-angular-resolution optical interferometric instrument PAVO at the CHARA array. We modelled angular diameters using 3D limb-darkening models and determined effective temperatures directly from the Stefan-Boltzmann relation, with an iterative procedure to interpolate over tables of bolometric corrections. Surface gravities (log(<i>g<i/>)) were estimated from comparisons to Dartmouth stellar evolution model tracks. We collected spectroscopic observations from the ELODIE and FIES spectrographs and estimated metallicities ([Fe/H]) from a 1D non-local thermodynamic equilibrium (NLTE) abundance analysis of unblended lines of neutral and singly ionised iron.<i>Results.<i/> We inferred <i>T<i/><sub>eff<sub/> to better than 1% for five of the stars (HD 103095, HD 122563, HD 127243, HD 140283, and HD 224930). The effective temperatures of the other five stars are reliable to between 2 and 3%; the higher uncertainty on the <i>T<i/><sub>eff<sub/> for those stars is mainly due to their having a larger uncertainty in the bolometric fluxes. We also determined log(<i>g<i/>) and [Fe/H] with median uncertainties of 0.03 dex and 0.09 dex, respectively. Conclusions. This study presents reliable and homogeneous fundamental stellar parameters for ten metal-poor stars that can be adopted as a new set of benchmarks. The parameters are based on our consistent approach of combining interferometric observations, 3D limb-darkening-modelling and spectroscopic observations. The next paper in this series will extend this approach to dwarfs and giants in the metal-rich regime. |
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| Item Description: | Gesehen am 18.09.2020 |
| Physical Description: | Online Resource |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/202037590 |