NLTE Analysis of High Resolution H-band Spectra. II. Neutral Magnesium

Abstract

Aiming at testing the validity of our magnesium atomic model and investigating the effects of non-local thermodynamical equilibrium (NLTE) on the formation of the H-band neutral magnesium lines, we derive the differential Mg abundances from selected transitions for 13 stars either adopting or relaxing the assumption of local thermodynamical equilibrium (LTE). Our analysis is based on high-resolution and high signal-to-noise ratio H-band spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and optical spectra from several instruments. The absolute differences between the Mg abundances derived from the two wavelength bands are always less than 0.1 dex in the NLTE analysis, while they are slightly larger for the LTE case. This suggests that our Mg atomic model is appropriate for investigating the NLTE formation of the H-band Mg lines. The NLTE corrections for the Mg I H-band lines are sensitive to the surface gravity, becoming larger for smaller log g values, and strong lines are more susceptible to departures from LTE. For cool giants, NLTE corrections tend to be negative, and for the strong line at 15765 Å they reach -0.14 dex in our sample, and up to -0.22 dex for other APOGEE stars. Our results suggest that it is important to include NLTE corrections in determining Mg abundances from the H-band Mg I transitions, especially when strong lines are used.

References in corpus (24)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• The Eleventh and Twelfth Data Releases of the Sloan Digital Sky Survey: Final Data from SDSS-III
• SDSS-III: Massive Spectroscopic Surveys of the Distant Universe, the Milky Way Galaxy, and Extra-Solar Planetary Systems
• First stars V - Abundance patterns from C to Zn and supernova yields in the early Galaxy
• Exploring the Milky Way stellar disk. A detailed elemental abundance study of 714 F and G dwarf stars in the Solar neighbourhood
• The Tenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Apache Point Observatory Galactic Evolution Experiment
• Elemental Abundance Survey of The Galactic Thick Disk
• ASPCAP: The Apogee Stellar Parameter and Chemical Abundances Pipeline
• Chemical composition of 90 F and G disk dwarfs
• A non-LTE study of neutral and singly-ionized iron line spectra in 1D models of the Sun and selected late-type stars
• First stars XII. Abundances in extremely metal-poor turnoff stars,and comparison with the giants
• Calibrations of Atmospheric Parameters Obtained from the First Year of SDSS-III APOGEE Observations
• Fossil Imprints of the First Generation Supernova Ejecta in Extremely Metal-Deficient Stars
• Non-LTE abundances of Mg and K in extremely metal-poor stars and the evolution of [O/Mg], [Na/Mg], [Al/Mg] and [K/Mg] in the Milky Way
• Oscillator Strengths and Damping Constants for Atomic Lines in the J and H Bands
• Mg line formation in late-type stellar atmospheres: I. The model atom
• Systematic NLTE study of the -2.6 < [Fe/H] < 0.2 F and G dwarfs in the solar neighbourhood. I. Stellar atmosphere parameters
• Inelastic Mg+H collision data for non-LTE applications in stellar atmospheres
• Geometry of giant star model atmospheres: A consistency test
• Astrophysical tests of atomic data important for stellar Mg abundance determinations
• Red Supergiant Stars as Cosmic Abundance Probes: NLTE Effects in J-band Iron and Titanium Lines
• Determining Ages of APOGEE Giants with Known Distances
• Red Supergiant Stars as Cosmic Abundance Probes. III. NLTE effects in J-band Magnesium lines
• Statistical equilibrium of silicon in the solar atmosphere

Cited by in corpus (12)

• APOGEE Data and Spectral Analysis from SDSS Data Release 16: Seven Years of Observations Including First Results from APOGEE-South
• Accuracy and precision of industrial stellar abundances
• APOGEE Data Releases 13 and 14: Stellar Parameter and Abundance Comparisons With Independent Analyses
• Chemical Abundances of Main-Sequence, Turnoff, Subgiant and red giant Stars from APOGEE spectra II: Atomic Diffusion in M67 Stars
• Chemical Abundances of Main-Sequence, Turn-off, Subgiant and red giant Stars from APOGEE spectra I: Signatures of Diffusion in the Open Cluster M67
• NLTE for APOGEE: Simultaneous Multi-Element NLTE Radiative Transfer
• The Gaia-ESO Survey: Evidence of atomic diffusion in M67?
• NLTE analysis of copper lines in different stellar populations
• The metal-rich halo component extended in z: a characterization with Gaia DR2 and APOGEE
• Stellar population astrophysics (SPA) with the TNG -- The Arcturus Lab
• Near-infrared chemical abundances of stars in the Sculptor dwarf galaxy
• Probing 3D and NLTE models using APOGEE observations of globular cluster stars