[Paper Review] The Gaia FGK Benchmark Stars - High resolution spectral library

S. Blanco-Cuaresma, C. Soubiran+2 more|arXiv (Cornell University)|Mar 12, 2014

Stellar, planetary, and galactic studies46 references60 citations

TL;DR

This paper presents a high-resolution, high-signal-to-noise spectral library of 34 Gaia FGK benchmark stars, compiled from NARVAL and HARPS data, to enable homogeneous calibration of stellar spectroscopic surveys. The library is fully automated, reproducible, and available in multiple formats with rigorous quality control, ensuring consistency across instruments and enabling improved accuracy in stellar parameter and abundance determinations for Galactic studies.

ABSTRACT

Context. An increasing number of high resolution stellar spectra is available today thanks to many past and ongoing spectroscopic surveys. Consequently, numerous methods have been developed in order to perform an automatic spectral analysis on a massive amount of data. When reviewing published results, biases arise and they need to be addressed and minimized. Aims. We are providing a homogeneous library with a common set of calibration stars (known as the Gaia FGK Benchmark Stars) that will allow to assess stellar analysis methods and calibrate spectroscopic surveys. Methods. High resolution and signal-to-noise spectra were compiled from different instruments. We developed an automatic process in order to homogenize the observed data and assess the quality of the resulting library. Results. We built a high quality library that will facilitate the assessment of spectral analyses and the calibration of present and future spectroscopic surveys. The automation of the process minimizes the human subjectivity and ensures reproducibility. Additionally, it allows us to quickly adapt the library to specific needs that can arise from future spectroscopic analyses.

Motivation & Objective

• To create a homogeneous, high-quality spectral library of benchmark stars to reduce biases in stellar parameter and abundance determinations from spectroscopic surveys.
• To provide a common reference set of stars beyond the Sun, covering diverse regions of the Hertzsprung-Russell diagram and metallicities from solar to -2.7 dex.
• To enable consistent calibration of current and future spectroscopic surveys by minimizing human subjectivity through automation.
• To support the Gaia mission's goal of deriving precise stellar parameters for one billion stars.
• To improve the comparability and reliability of stellar data across different surveys and analysis methods.

Proposed method

• Compilation of high-resolution, high-signal-to-noise spectra from NARVAL, HARPS, and ESO-ADP databases for 34 FGK benchmark stars.
• Application of an automated pipeline to homogenize data, including radial velocity correction, continuum normalization, and convolution to match target spectral resolution.
• Use of independent EW measurements and cross-instrument comparisons to validate spectral consistency and normalization quality.
• Creation of four library variants: convolved and non-convolved, normalized and non-normalized spectra in FITS and plain text formats.
• Identification and flagging of telluric absorption regions and spectral gaps using automated detection and metadata tagging.
• Implementation of rigorous quality control via comparison with high-precision HARPS pipeline results and independent EW measurements.

Experimental results

Research questions

• RQ1 How can a standardized, high-fidelity spectral library be constructed to minimize human bias in stellar spectral analysis?
• RQ2 To what extent does the automated processing pipeline ensure consistency across different instruments and data sets?
• RQ3 How well do the measured equivalent widths from different instruments agree, and what is the resulting uncertainty in abundance determinations?
• RQ4 Can the library be reliably used to calibrate diverse spectroscopic surveys with varying spectral resolutions and wavelength coverage?
• RQ5 What level of internal consistency and reproducibility can be achieved in a fully automated spectral library creation process?

Key findings

• The library contains 78 spectra from 34 benchmark stars, covering 480–680 nm with a wavelength sampling of 0.001 nm and signal-to-noise ratios sufficient for high-precision analysis.
• Internal consistency between instruments is excellent, with a mean relative equivalent width (EW) difference of 0.01 ± 0.01 (1%), indicating high reproducibility.
• Abundance analysis based on EWs shows a variation of only ±0.007 dex in metallicity when EWs are perturbed by 1%, confirming high precision.
• Radial velocity corrections were validated against HARPS pipeline results, confirming accuracy within the expected uncertainty.
• The library is available in multiple formats (FITS and plain text) with metadata, telluric region flags, and gap information for user-friendly application.
• The entire creation and validation process is automated, ensuring reproducibility and enabling rapid adaptation to new survey requirements.