Gaia FGK Benchmark Stars: New Candidates At Low-Metallicities

Abstract

We have entered an era of large spectroscopic surveys in which we can measure, through automated pipelines, the atmospheric parameters and chemical abundances for large numbers of stars. Calibrating these survey pipelines using a set of "benchmark stars" in order to evaluate the accuracy and precision of the provided parameters and abundances is of utmost importance. The recent proposed set of Gaia FGK benchmark stars of Heiter et al. (2015) has no recommended stars within the critical metallicity range of $-2.0<$ [Fe/H] $<-1.0$ dex. In this paper, we aim to add candidate Gaia benchmark stars inside of this metal-poor gap. We began with a sample of 21 metal-poor stars which was reduced to 10 stars by requiring accurate photometry and parallaxes, and high-resolution archival spectra. The procedure used to determine the stellar parameters was similar to Heiter et al. (2015) and Jofre et al. (2014) for consistency. The effective temperature (T${}_{\mathrm{eff}}$) of all candidate stars was determined using the Infrared Flux Method utilizing multi-band photometry. The surface gravity (log g) was determined through fitting stellar evolutionary tracks. The [Fe/H] was determined using four different spectroscopic methods fixing the T${}_{\mathrm{eff}}$ and log g from the values determined independent of spectroscopy. We discuss, star-by-star, the quality of each parameter including how it compares to literature, how it compares to a spectroscopic run where all parameters are free, and whether Fe I ionisation-excitation balance is achieved. From the 10 stars, we recommend a sample of five new metal-poor benchmark candidate stars which have consistent T${}_{\mathrm{eff}}$ , log g, and [Fe/H] determined through several means. These stars can be used for calibration and validation purpose of stellar parameter and abundance pipelines and should be of highest priority for future interferometric studies.

Accepted for publication in A&A, 18 Pages, 8 Figures, 7 Tables

References in corpus (17)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey
• The GALAH Survey: Scientific Motivation
• Determining stellar atmospheric parameters and chemical abundances of FGK stars with iSpec
• Scaled solar tracks and isochrones in a large region of the Z-Y plane I. From the ZAMS to the TP-AGB end for 0.15 - 2.5 Mo stars
• A new implementation of the infrared flux method using the 2MASS catalogue
• DAOSPEC: an automatic code for measuring equivalent widths in high-resolution stellar spectra
• Gaia-ESO Survey: The analysis of high-resolution UVES spectra of FGK-type stars
• Accurate fundamental parameters for Lower Main Sequence Stars
• The Gaia FGK Benchmark Stars - High resolution spectral library
• An accurate and self-consistent chemical abundance catalogue for the APOGEE/Kepler sample
• VLT/FLAMES spectroscopy of red giant branch stars in the Fornax dwarf spheroidal galaxy
• Fundamental properties of the Population II fiducial stars HD 122563 and Gmb 1830 from CHARA interferometric observations
• Benchmark stars for Gaia: fundamental properties of the Population II star HD140283 from interferometric, spectroscopic and photometric data
• Searching for the metal-weak thick disc in the solar neighbourhood
• The AMBRE Project: Parameterisation of FGK-type stars from the ESO:HARPS archived spectra
• New solar twins and the metallicity and temperature scales of the Geneva Copenhagen Survey

Cited by in corpus (38)

• The Gaia mission
• The GALAH+ Survey: Third Data Release
• Modern stellar spectroscopy caveats
• The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation
• Atomic data for the Gaia-ESO Survey
• Accuracy and precision of industrial stellar abundances
• APOGEE Data Releases 13 and 14: Stellar Parameter and Abundance Comparisons With Independent Analyses
• The Gaia-ESO Survey. Mg-Al anti-correlation in iDR4 globular clusters
• The Gaia-ESO Public Spectroscopic Survey: Motivation, implementation, GIRAFFE data processing, analysis, and final data products
• An accurate and self-consistent chemical abundance catalogue for the APOGEE/Kepler sample
• The GALAH Survey: Chemical tagging and chrono-chemodynamics of accreted halo stars with GALAH+ DR3 and $Gaia$ eDR3
• Gaia FGK Benchmark stars: Opening the black box of stellar element abundance determination
• The Gaia-ESO Survey: calibration strategy
• The Gaia-ESO Survey: homogenisation of stellar parameters and elemental abundances
• Fundamental stellar parameters of benchmark stars from CHARA interferometry. I. Metal-poor stars
• The Fastest Travel Together: Chemical Tagging of the Fastest Stars in Gaia DR2 to the Stellar Halo
• PEPSI deep spectra. II. Gaia benchmark stars and other M-K standards
• Atmospheric stellar parameters for large surveys using FASMA, a new spectral synthesis package
• ATHOS: On-the-fly stellar parameter determination of FGK stars based on flux ratios from optical spectra
• Effective Temperatures of Low-Mass Stars from High-Resolution H-band Spectroscopy
• The Gaia FGK benchmark stars version 2.1
• Titans metal-poor reference stars. I. Accurate effective temperatures and surface gravities for dwarfs and subgiants from 3D non-LTE H$\alpha$ profiles and Gaia parallaxes
• Chronology of the chemical enrichment of the old Galactic stellar populations
• Stellar Parameters and Chemical Abundances Estimated from LAMOST-II DR8 MRS based on Cycle-StarNet
• A high-precision abundance analysis of the nuclear benchmark star HD 20
• Titans metal-poor reference stars II. Red giants and CEMP stars
• Stellar twins determine the distance of the Pleiades
• A Comparison of the Chemical Composition of Main Sequence and Giant Stars in the Open Cluster NCC 752
• On the Origin of Metal-poor Stars in the Solar Neighborhood
• The Kepler Smear Campaign: Light curves for 102 Very Bright Stars
• LOTUS: A (non-)LTE Optimization Tool for Uniform derivation of Stellar atmospheric parameters
• On the physical nature of the Wilson-Bappu effect: revising the gravity and temperature dependence
• One of Everything: The Breakthrough Listen Exotica Catalog
• J01020100-7122208: an accreted evolved blue straggler that wasn't ejected from a supermassive black hole
• Benchmark stars, benchmark spectrographs: Detailed spectroscopic comparison of ESPRESSO, PEPSI, and HARPS data for Gaia benchmark stars
• The COMBS Survey -- III. The Chemodynamical Origins of Metal-Poor Bulge Stars
• LRPayne: Stellar parameters and abundances from low-resolution spectra
• Gaia FGK Benchmark Stars: Selecting Infrared Lines for Abundance Determination