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arXiv 2109.06203astro-ph.SR
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来自CHARA干涉测量的基准星的基本恒星参数-- II。矮星

Fundamental stellar parameters of benchmark stars from CHARA interferometry -- II. Dwarf stars

I. Karovicova, T. R. White, T. Nordlander, L. Casagrande, M. Ireland, D. Huber

摘要:

应用于银河系大型恒星巡天的恒星模型需要根据具有高度可靠的基本恒星参数的恒星样本进行适当的测试。我们已经建立了一个计划,旨在提供这样的样品。我们提出了新的基本恒星参数的九个矮星,将被用作大型恒星调查的基准。其中一颗恒星是太阳双星18 Sco,它是Gaia-ESO基准之一。目标是在Teff中达到1%的精度。这一精度对于精确确定巡天观测到的恒星的全部基本参数和丰度非常重要。利用高角分辨率的光学干涉仪PAVO/CHARA,我们观测了HD 131156(xiBoo),HD 146233(18 Sco),HD 152391,HD 173701,HD 185395(thetaCyg),HD 186408(16 CygA),HD 186427(16 CygB),HD 190360和HD 207978(15 Peg)。我们从3D模型大气中推导出边缘变暗校正,并直接从Stefan-Boltzmann关系确定Teff,并采用迭代程序在测热校正表上进行插值。通过与达特茅斯恒星演化模型轨道的比较,估计了表面重力。我们收集了光谱观测从ESDIE光谱仪和估计金属丰度([Fe/H])从一维非局部热力学平衡(NLTE)丰度分析的中性和单离子化铁的未混合线。对于九颗星中的八颗,我们测量的Teff小于1%,对于一颗星,优于2%。我们确定了logg和Fe/H的中值不确定度分别为0.015dex和0.05dex。这项研究提出了更新的基本恒星参数的九个矮星,可用作一套新的基准。所有参数的基础上一贯相结合的干涉观测,3D临暗建模和光谱分析。下一篇论文将把我们的样本扩展到富金属巨星。

英文摘要:

Stellar models applied to large stellar surveys of the Milky Way need to be properly tested against a sample of stars with highly reliable fundamental stellar parameters. We have established a program aiming to deliver such a sample. We present new fundamental stellar parameters of nine dwarfs that will be used as benchmarks for large stellar surveys. One of these stars is the solar-twin 18Sco, which is one of the Gaia-ESO benchmarks. The goal is to reach a precision of 1% in Teff. This precision is important for accurate determinations of the full set of fundamental parameters and abundances of stars observed by the surveys. We observed HD131156 (xiBoo), HD146233 (18Sco), HD152391, HD173701, HD185395 (thetaCyg), HD186408 (16CygA), HD186427 (16CygB), HD190360 and HD207978 (15Peg) using the high angular resolution optical interferometric instrument PAVO/CHARA. We derived limb-darkening corrections from 3D model atmospheres and determined Teff directly from the Stefan-Boltzmann relation, with an iterative procedure to interpolate over tables of bolometric corrections. Surface gravities were estimated from comparisons to Dartmouth stellar evolution model tracks. We collected spectroscopic observations from the ELODIE spectrograph and estimated metallicities ([Fe/H]) from a 1D non-local thermodynamic equilibrium (NLTE) abundance analyses of unblended lines of neutral and singly ionized iron. For eight of the nine stars, we measure the Teff less than 1%, and for one star better than 2%. We determined the median uncertainties in logg and Fe/H as 0.015dex and 0.05dex, respectively. This study presents updated fundamental stellar parameters of nine dwarfs that can be used as a new set of benchmarks. All parameters were based on consistently combining interferometric observations, 3D limb-darkening modelling and spectroscopic analysis. The next paper will extend our sample to metal-rich giants.

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