LOTUS: A (non-)LTE Optimization Tool for Uniform derivation of Stellar atmospheric parameters

Abstract

Precise fundamental atmospheric stellar parameters and abundance determination of individual elements in stars are important for all stellar population studies. Non-Local Thermodynamic Equilibrium (Non-LTE; hereafter NLTE) models are often important for such high precision, however, can be computationally complex and expensive, which renders the models less utilized in spectroscopic analyses. To alleviate the computational burden of such models, we developed a robust 1D, LTE and NLTE fundamental atmospheric stellar parameter derivation tool, $\text{LOTUS}$, to determine the effective temperature $T_{\mathrm{eff}}$, surface gravity $\log g$, metallicity $\mbox{[Fe/H]}$ and microturbulent velocity $v_{\mathrm{mic}}$ for FGK type stars, from equivalent width (EW) measurements of Fe I and Fe II lines. We utilize a generalized curve of growth method to take into account the EW dependencies of each Fe I and Fe II line on the corresponding atmospheric stellar parameters. A global differential evolution optimization algorithm is then used to derive the optimized fundamental parameters. Additionally, $\text{LOTUS}$ can determine precise uncertainties for each stellar parameter using a Markov Chain Monte Carlo (MCMC) algorithm. We test and apply $\text{LOTUS}$ on a sample of benchmark stars, as well as stars with available asteroseismic surface gravities from the K2 survey, and metal-poor stars from $R$-process Alliance (RPA) survey. We find very good agreement between our NLTE-derived parameters in $\text{LOTUS}$ to non-spectroscopic values within $T_{\mathrm{eff}}=\pm 30$ K and $\log g=\pm 0.10$ dex for benchmark stars. We provide open access of our code, as well as of the interpolated pre-computed NLTE EW grids available on Github, and documentation with working examples on Readthedocs.

42 pages, 12 figures, 3 tables, accepted for publication in AJ. For Code on Github, see: https://github.com/Li-Yangyang/LOTUS. For Code Documentation, see: https://lotus-nlte.readthedocs.io/en/latest/

References in corpus (33)

• Array Programming with NumPy
• The NumPy array: a structure for efficient numerical computation
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• The Dartmouth Stellar Evolution Database
• Galactic chemical evolution: Carbon through Zinc
• 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
• Modern stellar spectroscopy caveats
• 4MOST: Project overview and information for the First Call for Proposals
• ARES v2 - new features and improved performance
• Non-LTE line formation of Fe in late-type stars - III. 3D non-LTE analysis of metal-poor stars
• Atomic data for the Gaia-ESO Survey
• Automated derivation of stellar atmospheric parameters and chemical abundances: the MATISSE algorithm
• The $R$-Process Alliance: Fourth Data Release from the Search for $r$-Process-Enhanced Stars in the Galactic Halo
• Mg line formation in late-type stellar atmospheres: I. The model atom
• PLATO as it is: a legacy mission for Galactic archaeology
• The GALAH Survey: Non-LTE departure coefficients for large spectroscopic surveys
• The R-process Alliance: First Magellan/MIKE Release from the Southern Search for R-Process-enhanced Stars
• The formation of the Milky Way halo and its dwarf satellites; a NLTE-1D abundance analysis. II. Early chemical enrichment
• 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
• Non-LTE Radiative Transfer with Turbospectrum
• Accurate effective temperatures of the metal-poor benchmark stars HD 140283, HD 122563 and HD 103095 from CHARA interferometry
• 3D non-LTE iron abundances in FG-type dwarfs
• The limb-darkened Arcturus; Imaging with the IOTA/IONIC interferometer
• Fundamental stellar parameters of benchmark stars from CHARA interferometry. I. Metal-poor stars
• Atmospheric parameters and chemical properties of red giants in the CoRoT asteroseismology fields
• Spectroscopic study of red giants in the Kepler field with asteroseismologically established evolutionary status and stellar parameters
• On the iron ionization balance of cool stars
• Fundamental stellar parameters of benchmark stars from CHARA interferometry -- II. Dwarf stars
• First detection of oscillations in the Halo giant HD 122563: validation of seismic scaling relations and new fundamental parameters
• Fundamental stellar parameters of benchmark stars from CHARA interferometry -- III. Giant and subgiant stars

Cited by in corpus (5)

• NLTE abundances of Eu for a sample of metal-poor stars in the Galactic Halo and Metal-poor Disk with 1D and <3D> models
• Stellar Population Astrophysics (SPA) with the TNG: NLTE atmospheric parameters and abundances of giant stars in 33 Open Clusters
• Discovery of a Metal-Poor Red Giant Star with the Highest Ultra-Lithium Enhancement
• A multi-technique detection of an eccentric giant planet around accelerating star HD 57625
• Investigating non-LTE abundances of Neodymium (Nd) in metal-poor FGK stars