Effective temperature determinations of late-type stars based on 3D non-LTE Balmer line formation

Abstract

Hydrogen Balmer lines are commonly used as spectroscopic effective temperature diagnostics of late-type stars. However, the absolute accuracy of classical methods that are based on one-dimensional (1D) hydrostatic model atmospheres and local thermodynamic equilibrium (LTE) is still unclear. To investigate this, we carry out 3D non-LTE calculations for the Balmer lines, performed, for the first time, over an extensive grid of 3D hydrodynamic STAGGER model atmospheres. For H$\alpha$, H$\beta$, and H$\gamma$, we find significant 1D non-LTE versus 3D non-LTE differences (3D effects): the outer wings tend to be stronger in 3D models, particularly for H$\gamma$, while the inner wings can be weaker in 3D models, particularly for H$\alpha$. For H$\alpha$, we also find significant 3D LTE versus 3D non-LTE differences (non-LTE effects): in warmer stars ($T_{\text{eff}}\approx 6500$K) the inner wings tend to be weaker in non-LTE models, while at lower effective temperatures ($T_{\text{eff}}\approx 4500$K) the inner wings can be stronger in non-LTE models; the non-LTE effects are more severe at lower metallicities. We test our 3D non-LTE models against observations of well-studied benchmark stars. For the Sun, we infer concordant effective temperatures from H$\alpha$, H$\beta$, and H$\gamma$; however the value is too low by around 50K which could signal residual modelling shortcomings. For other benchmark stars, our 3D non-LTE models generally reproduce the effective temperatures to within $1\sigma$ uncertainties. For H$\alpha$, the absolute 3D effects and non-LTE effects can separately reach around 100K, in terms of inferred effective temperatures. For metal-poor turn-off stars, 1D LTE models of H$\alpha$ can underestimate effective temperatures by around 150K. Our 3D non-LTE model spectra are publicly available, and can be used for more reliable spectroscopic effective temperature determinations.

arXiv comment19 pages, 10 figures, abstract abridged; accepted for publication in Astronomy & Astrophysics

References in corpus (36)

• The chemical composition of the Sun
• 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
• Nominal values for selected solar and planetary quantities: IAU 2015 Resolution B3
• NLTE line formation of Fe for late-type stars. I. Standard stars with 1D and <3D> model atmospheres
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• Oxygen Abundances in Nearby FGK Stars and the Galactic Chemical Evolution of the Local Disk and Halo
• Spectroscopic analysis of DA white dwarfs with 3D model atmospheres
• NLTE abundances of Mn in a sample of metal-poor stars
• Non-LTE line formation of Fe in late-type stars - III. 3D non-LTE analysis of metal-poor stars
• Improvements to stellar structure models, based on a grid of 3D convection simulations. II. Calibrating the mixing-length formulation
• Systematic non-LTE study of the $-2.6\le$ [Fe/H] $\le 0.2$ F and G dwarfs in the solar neighbourhood. II. Abundance patterns from Li to Eu
• The Stagger-grid: A grid of 3D stellar atmosphere models - III. The relation to mixing-length convection theory
• Detailed analysis of Balmer lines in cool dwarf stars
• The Gaia FGK Benchmark Stars - High resolution spectral library
• Non-LTE oxygen line formation in 3D hydrodynamic model stellar atmospheres
• Non-LTE line-formation for hydrogen revisited
• Kinetic equilibrium of iron in the atmospheres of cool stars III. The ionization equilibrium of selected reference stars
• Accurate abundance analysis of late-type stars: advances in atomic physics
• How realistic are solar model atmospheres?
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• Three Ancient Halo Subgiants: Precise Parallaxes, Compositions, Ages, and Implications for Globular Clusters
• Unveiling systematic biases in 1D LTE excitation-ionisation balance of Fe for FGK stars. A novel approach to determination of stellar parameters
• The Stagger-grid: A Grid of 3D Stellar Atmosphere Models - II. Horizontal and Temporal Averaging and Spectral Line Formation
• Solution to the problem of the surface gravity distribution of cool DA white dwarfs from improved 3D model atmospheres
• IRIS: A Generic Three-Dimensional Radiative Transfer Code
• Non-LTE Balmer line formation in late-type spectra: Effects of atomic processes involving hydrogen atoms
• Accurate effective temperatures of the metal-poor benchmark stars HD 140283, HD 122563 and HD 103095 from CHARA interferometry
• Impact of granulation effects on the use of Balmer lines as temperature indicators
• Three-dimensional interferometric, spectrometric, and planetary views of Procyon
• The solar hydrogen spectrum in non-LTE
• The Gaia-ESO survey: Hydrogen lines in red giants directly trace stellar mass
• On line contribution functions and examining spectral line formation in 3D model stellar atmospheres
• An Assessment of and Solution to the Intensity Diffusion Error Intrinsic to Short-Characteristic Radiative Transfer Methods

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