Mg line formation in late-type stellar atmospheres: I. The model atom

Abstract

Mg is often traced in late-type stars using lines of neutral magnesium, which is expected to be subject to departures from LTE. The astrophysical importance of Mg as well as its relative simplicity from an atomic physics point of view, makes it a prime target and test bed for detailed ab initio non-LTE modelling in stellar atmospheres. For the low-lying states of Mg i, electron collision data were calculated using the R-matrix method. Calculations for collisional broadening by neutral hydrogen were also performed where data were missing. These calculations, together with data from the literature, were used to build a model atom. First, the modelling was tested by comparisons with observed spectra of benchmark stars with well-known parameters. Second, the spectral line behaviour and uncertainties were explored by extensive experiments in which sets of collisional data were changed or removed. The modelled spectra agree well with observed spectra. The line-to-line scatter in the derived abundances shows improvements compared to LTE. The observed Mg emission features at 7 and 12 microns in the spectra of the Sun and Arcturus are reasonably well reproduced. The modelling predicts non-LTE abundance corrections in dwarfs, both solar metallicity and metal-poor, to be very small (of order 0.01 dex), even smaller than found in previous studies. In giants, corrections vary greatly between lines, but can be as large as 0.4 dex. Our results emphasise the need for accurate data of Mg collisions with both electrons and H atoms for precise non-LTE predictions of stellar spectra, but demonstrate that such data can be calculated and that ab initio non-LTE modelling without resort to free parameters is possible. Grids of departure coefficients and abundance corrections for a range of stellar parameters are planned for a forthcoming paper.

arXiv comment23 pages, 11 figures

References in corpus (42)

• The chemical composition of the Sun
• The Gaia mission
• Validation of the new Hipparcos reduction
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• SDSS-III: Massive Spectroscopic Surveys of the Distant Universe, the Milky Way Galaxy, and Extra-Solar Planetary Systems
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE)
• Elemental Abundance Survey of The Galactic Thick Disk
• The GALAH Survey: Scientific Motivation
• An absolutely calibrated effective temperature scale from the InfraRed Flux Method
• Non-LTE calculations for neutral Na in late-type stars using improved atomic data
• NLTE line formation of Fe for late-type stars. I. Standard stars with 1D and <3D> model atmospheres
• NLTE line formation of Fe in late-type stars II: 1D spectroscopic stellar parameters
• Departures from LTE for neutral Li in late-type stars
• Gaia FGK Benchmark Stars - Metallicity
• New ATLAS9 And MARCS Model Atmosphere Grids for the Apache Point Observatory Galactic Evolution Experiment (APOGEE)
• The elemental composition of the Sun I. The intermediate mass elements Na to Ca
• Spectroscopic Signatures of Convection in the Spectrum of Procyon. Fundamental Parameters and Iron Abundance
• Fundamental Parameters and Chemical Composition of Arcturus
• A non-LTE study of neutral and singly-ionized calcium in late-type stars
• An Open Source, Massively Parallel Code for Non-LTE Synthesis and Inversion of Spectral Lines and Zeeman-induced Stokes Profiles
• The lithium isotopic ratio in very metal-poor stars
• On OH line formation and oxygen abundances in metal-poor stars
• Inelastic H+Li and H^-+Li^+ collisions and non-LTE Li I line formation in stellar atmospheres
• Non-LTE line formation for heavy elements in four very metal-poor stars
• On inelastic hydrogen atom collisions in stellar atmospheres
• Excitation and charge transfer in low-energy hydrogen atom collisions with neutral atoms: Theory, comparisons, and application to Ca
• Automatic stellar spectra parameterisation in the IR CaII triplet region
• Inelastic Na+H collision data for non-LTE applications in stellar atmospheres
• Inelastic Mg+H collision data for non-LTE applications in stellar atmospheres
• Astrophysical tests of atomic data important for stellar Mg abundance determinations
• The Stagger-grid: A Grid of 3D Stellar Atmosphere Models - II. Horizontal and Temporal Averaging and Spectral Line Formation
• Benchmark stars for Gaia: fundamental properties of the Population II star HD140283 from interferometric, spectroscopic and photometric data
• A NLTE line blanketed model of a solar type star
• Effective temperatures, rotational velocities, microturbulent velocities and abundances in the atmospheres of the Sun,. HD1835 and HD10700
• A grid of NLTE corrections for magnesium and calcium in late-type giant and supergiant stars: application to Gaia
• Effects of line-blocking on the non-LTE Fe I spectral line formation
• Is the solar spectrum latitude dependent? An investigation with SST/TRIPPEL
• Experimental Mg I oscillator strengths and radiative lifetimes for astrophysical applications on metal-poor stars - New data for the Mg I b triplet
• Non-LTE Abundances and Consequences for the Evolution of the alpha elements in the Galaxy
• Non-LTE modeling of the near UV band of late-type stars
• Mg I emission lines at 12 and 18 micrometer in K giants
• The Zeeman-sensitive emission lines of Mg I at 12 micron in Procyon

Cited by in corpus (71)

• The chemical make-up of the Sun: A 2020 vision
• The GALAH+ Survey: Third Data Release
• Spectroscopy Made Easy: Evolution
• The GALAH Survey: Second Data Release
• Spectral Properties of Cool Stars: Extended Abundance Analysis of 1617 Planet Search Stars
• Observational constraints on the origin of the elements. IV: The standard composition of the Sun
• Accuracy and precision of industrial stellar abundances
• Gaia FGK benchmark stars: abundances of alpha and iron-peak elements
• Observational constraints on the origin of the elements. I. 3D NLTE formation of Mn lines in late-type stars
• Non-LTE aluminium abundances in late-type stars
• Non-local thermodynamic equilibrium stellar spectroscopy with 1D and <3D> models - I. Methods and application to magnesium abundances in standard stars
• Accurate abundance analysis of late-type stars: advances in atomic physics
• The GALAH Survey: Non-LTE departure coefficients for large spectroscopic surveys
• Solar oxygen abundance
• Influence of sub- and super-solar metallicities on the compositions of solid planetary building blocks
• Semi-empirical Modeling of the Photosphere, Chromosphere, Transition Region, and Corona of the M-dwarf Host Star GJ 832
• 3D NLTE analysis of the most iron-deficient star, SMSS0313-6708
• Excitation and charge transfer in low-energy hydrogen atom collisions with neutral atoms: Theory, comparisons, and application to Ca
• Inelastic O+H collisions and the OI 777nm solar centre-to-limb variation
• High-precision abundances of elements in Kepler LEGACY stars. Verification of trends with stellar age
• Detailed Abundances in the Ultra-faint Magellanic Satellites Carina II and III
• NLTE Chemical abundances in Galactic open and globular clusters
• NLTE for APOGEE: Simultaneous Multi-Element NLTE Radiative Transfer
• Mg line formation in late-type stellar atmospheres: II. Calculations in a grid of 1D models
• A Model of the H$\alpha$ and Na Transmission Spectrum of HD 189733b
• The GALAH Survey: Verifying abundance trends in the open cluster M67 using non-LTE spectroscopy
• The Solar Twin Planet Search. V. Close-in, low-mass planet candidates and evidence of planet accretion in the solar twin HIP 68468
• PySME -- Spectroscopy Made Easier
• NLTE line formation for Mg\ione\ and Mg\ii\ in atmospheres of B-A-F-G-K stars
• Ultra metal-poor stars: Spectroscopic determination of stellar atmospheric parameters using iron Non-LTE line abundances
• Non-LTE abundance corrections for late-type stars from 2000Å to 3μm: I. Na, Mg, and Al
• Non-local thermodynamic equilibrium stellar spectroscopy with 1D and 3D models - II. Chemical properties of the Galactic metal-poor disc and the halo
• Globular Cluster Abundances from High-Resolution, Integrated-Light Spectroscopy. II. Expanding the Metallicity Range for Old Clusters and Updated Analysis Techniques
• Ca line formation in late-type stellar atmospheres: I. The model atom
• Detailed chemical abundances of stars in the outskirts of the Tucana II ultra-faint dwarf galaxy
• A hydrodynamic study of the escape of metal species and excited hydrogen from the atmosphere of the hot Jupiter WASP-121b
• Solar and Stellar Photospheric Abundances
• Inelastic e+Mg collision data and its impact on modelling stellar and supernova spectra
• The GAPS Programme at TNG -- XXV. Stellar atmospheric parameters and chemical composition through GIARPS optical and near-infrared spectra
• Chemical Characterization of the Inner Galactic bulge:North-South Symmetry
• High Resolution Optical Spectroscopy of Stars in the Sylgr Stellar Stream
• The homogeneous characterisation of Ariel host stars
• Excitation and charge transfer in low-energy hydrogen atom collisions with neutral oxygen
• Titanium abundances in late-type stars I. 1D non-local thermodynamic equilibrium modelling in benchmark dwarfs and giants
• An empirical recipe for inelastic hydrogen-atom collisions in non-LTE calculations
• NLTE Analysis of High Resolution H-band Spectra. II. Neutral Magnesium
• NLTE modelling of integrated light spectra. Abundances of barium, magnesium, and manganese in a metal-poor globular cluster
• The GALAH Survey: Using Galactic Archaeology to Refine our Knowledge of TESS Target Stars
• Detailed $\alpha$ abundance trends in the inner Galactic bulge
• High Resolution Spectroscopic Abundances of Red Giant Branch Stars in NGC 6681
• Revisiting inelastic Cu+H collisions and the non-LTE Galactic evolution of copper
• Sun-like stars unlike the Sun: Clues for chemical anomalies of cool stars
• The Mg I b triplet and the 4571 Å line as diagnostics of stellar chromospheric activity
• A distinct halo population revealed from 3D non-LTE magnesium abundances
• Non-LTE iron abundances in cool stars: The role of hydrogen collisions
• Excitation and charge transfer in low-energy hydrogen atom collisions with neutral manganese and titanium
• Probing 3D and NLTE models using APOGEE observations of globular cluster stars
• Mg/Si mineralogical ratio of low-mass planet hosts. Correction for the NLTE effects
• Atomic diffusion and mixing in old stars VII. Abundances of Mg, Ti, and Fe in M30
• LOTUS: A (non-)LTE Optimization Tool for Uniform derivation of Stellar atmospheric parameters
• Magnetic field inference from the spectral region around the Mg I $b_2$ line using the weak-field approximation
• Discovery of a Metal-Poor Red Giant Star with the Highest Ultra-Lithium Enhancement
• Abundance Pattern Fitting with Bayesian Inference: Constraining First Stars' Properties and Their Explosion Mechanism with Extremely Metal-poor Stars
• Modeling the Mg I from the NUV to MIR. II. Testing stellar models
• Modeling the MgI from the NUV to MIR: I. The Solar Case
• Omega Centauri: weak MgH-band in red giants directly trace the helium content
• The NLTE Analyses of Carbon Emission Lines in the Atmospheres of O and B type Stars
• The Stellar Abundances and Galactic Evolution Survey (SAGES). IV. Surface Gravity Estimation and Giant-Dwarf Separation with the DDO51 Filter
• The odd bunch: chrono-chemo-dynamics of sixteen unusual stars from Kepler
• The COMBS Survey -- III. The Chemodynamical Origins of Metal-Poor Bulge Stars
• A Near-Infrared and Optical Study of NGC 5822: An Open Cluster Hosting Barium-stars and Lithium-Enriched Giant Stars