The Alpha Centauri Binary System: Atmospheric Parameters and Element Abundances

Abstract

The alpha Centauri binary system, owing to its duplicity, proximity and brightness, and its components' likeness to the Sun, is a fundamental calibrating object for the theory of stellar structure and evolution and the determination of stellar atmospheric parameters. This role, however, is hindered by a considerable disagreement in the published analyses of its atmospheric parameters and abundances. We report a new spectroscopic analysis of both components of the alpha Centauri binary system and compare published analyses of the system. The analysis is differential with respect to the Sun, based on high-quality spectra, and employed spectroscopic and photometric methods to obtain as many independent Teff determinations as possible. The atmospheric parameters are also checked for consistency against the results of the dynamical analysis and the positions of the components in a theoretical HR diagram. We discuss possible origins of discrepancies, concluding that the presence of NLTE effects is a probable candidate, but we note that there is as yet no consensus on the existence and cause of an offset between the spectroscopic and photometric Teff scales of cool dwarfs. The spectroscopic surface gravities also agree with those derived from directly measured masses and radii. The abundance pattern can be deemed normal in the context of recent data on metal-rich stars. The position of alpha Cen A in an up-to-date theoretical evolutionary diagrams yields a good match of the evolutionary mass and age with those from the dynamical solution and seismology.

17 pages, 10 figures, accepted by A&A. Replacing the older version with this new, refereed, one. Main modifications concern an updated discussion of the impact of systematic offsets between different temperature scales and non-LTE effects on the determination of abundances and atmospheric parameters. The abstract is abridged

References in corpus (36)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• Evolutionary tracks and isochrones for low- and intermediate-mass stars: from 0.15 to 7 M_sun, and from Z=0.0004 to 0.03
• Spectroscopic [Fe/H] for 98 extra-solar planet-host stars: Exploring the probability of planet formation
• alpha-, r-, and s-process element trends in the Galactic thin and thick disks
• The effective temperature scale of FGK stars. II. Teff : color : [Fe/H] calibrations
• The YY Isochrones for alpha-element Enhanced Mixtures
• S4N: A Spectroscopic Survey of Stars in the Solar Neighborhood
• The Y^2 Stellar Evolutionary Tracks
• Spectroscopic metallicities for planet-host stars: extending the samples
• The effective temperature scale of FGK stars. I. Determination of temperatures and angular diameters with the infrared flux method
• Effective temperature scale and bolometric corrections from 2MASS photometry
• The colours of the Sun
• Oxygen Abundances in Nearby Stars. Clues to the formation and evolution of the Galactic disk
• Accurate fundamental parameters for Lower Main Sequence Stars
• Constraining fundamental stellar parameters using seismology. Application to Alpha Centauri AB
• The diameters of Alpha Centauri A and B - A comparison of the asteroseismic and VINCI/VLTI views
• Constraining the difference in convective blueshift between the components of alpha Cen with precise radial velocities
• C, S, Zn and Cu abundances in planet-harbouring stars
• Abundance Analysis of Planetary Host Stars I. Differential Iron Abundances
• Analysis of alpha Centauri AB including seismic constraints
• Chemical abundances of planet-host stars: Results for alpha and Fe-group elements
• High precision effective temperatures for 181 F--K dwarfs from line-depth ratios
• Magnesium isotope ratios in Hyades stars
• Models of alpha Centauri A and B with and without seismic constraints: time dependence of the mixing-length parameter
• On the difference between nuclear and contraction ages
• Grids of stellar models. VIII. From 0.4 to 1.0 Msun at Z=0.020 and Z=0.001, with the MHD equation of state
• Oxygen from the Lambda 7774 High-Excitation Triplet in Open Cluster Dwarfs: Hyades
• Are Proxima and Alpha Centauri Gravitationally Bound?
• A new seismic analysis of Alpha Centauri
• Astrobiologically Interesting Stars within 10 parsecs of the Sun
• Fine structure of the chromospheric activity in Solar-type stars - The Halpha Line
• Abundances of Mn, Co and Eu in a sample of 20 F-G disk stars: the influence of hyperfine structure splitting
• On the determination of oxygen abundances in chromospherically active stars
• The age of the Galactic thin disk from Th/Eu nucleocosmochronology I. Determination of [Th/Eu] abundance ratios
• Model Photospheres for Late-Type Stars from the Inversion of High-Resolution Spectroscopic Observations. The Sun
• The Chemical Composition of Alpha Centauri A: Strong Lines and the ABO Theory of Collisional Line Broadening

Cited by in corpus (48)

• Accurate masses and radii of normal stars: modern results and applications
• The FIP and Inverse FIP Effects in Solar and Stellar Coronae
• Testing a Predictive Theoretical Model for the Mass Loss Rates of Cool Stars
• Gaia FGK Benchmark Stars: Effective temperatures and surface gravities
• Stellar Abundances in the Solar Neighborhood: The Hypatia Catalog
• Accurate fundamental parameters for 23 bright solar-type stars
• Gaia FGK benchmark stars: abundances of alpha and iron-peak elements
• Lithium depletion in solar-like stars: no planet connection
• Improved stellar parameters of CoRoT-7
• Enhanced production of barium in low-mass stars: evidence from open clusters
• A Stellar Model-fitting Pipeline for Asteroseismic Data from the Kepler Mission
• Accurate and homogeneous abundance patterns in solar-type stars of the solar neighbourhood: a chemo-chronological analysis
• Evolution of the solar activity over time and effects on planetary atmospheres. II. kappa^1 Ceti, an analog of the Sun when life arose on Earth
• Stellar parameters for TRAPPIST-1
• The radii and limb darkenings of Alpha Centauri A and B - Interferometric measurements with VLTI/PIONIER
• A large sample of calibration stars for Gaia: log g from Kepler and CoRoT
• Automatic Determination of Stellar Parameters via Asteroseismology of Stochastically Oscillating Stars: Comparison with Direct Measurements
• Classically and Asteroseismically constrained 1D Stellar Evolution Models of $\alpha$ Centauri A and B using Empirical Mixing Length Calibrations
• X-Ray, FUV, and UV Observations of alpha Centauri B: Determination of Long-term Magnetic Activity Cycle and Rotation Period
• New Methods for Finding Activity-Sensitive Spectral Lines: Combined Visual Identification and an Automated Pipeline Find a Set of 40 Activity Indicators
• Reinvestigating $\alpha$ Cen AB in light of asteroseismic forward and inverse methods
• Uncertainties in grid-based estimates of stellar mass and radius. SCEPtER: Stellar CharactEristics Pisa Estimation gRid
• A photometric and spectroscopic survey of solar twin stars within 50 parsecs of the Sun: I. Atmospheric parameters and color similarity to the Sun
• Parallax and masses of alpha Centauri revisited
• Time evolution of high-energy emissions of low-mass stars:I. Age determination using stellar chronology with white dwarfs in wide binaries
• Benchmark ages for the Gaia benchmark stars
• Core properties of alpha Cen A using asteroseismology
• Evolutionary models for ultracool dwarfs
• $\alpha$ Centauri A in the far infrared
• The photospheric solar oxygen project: II. Non-concordance of the oxygen abundance derived from two forbidden lines
• The chemical composition of $\alpha$ Cen AB revisited
• The Mt John University Observatory Search For Earth-mass Planets In The Habitable Zone Of Alpha Centauri
• How dusty is alpha Centauri? Excess or non-excess over the infrared photospheres of main-sequence stars
• Accurate effective temperature from H$\alpha$ profiles
• Implications of the spectroscopic abundances in α Centauri A and B
• Spectral Line Depth Variability in Radial Velocity Spectra
• Coronae of Stars with Super Solar Elemental Abundances
• Fine Structure of the Age-Chromospheric Activity Relation in Solar-Type Stars: II. H$\alpha$ Line
• Density Conversion between 1-D and 3-D Stellar Models with 1D-MESA2HYDRO-3D
• Overview and Validation of the Asteroseismic Modeling Portal v2.0
• WASP 0639-32: a new F-type subgiant/K-type main-sequence detached eclipsing binary from the WASP project
• One of Everything: The Breakthrough Listen Exotica Catalog
• Comparison of chromospheric diagnostics in a 3D model atmosphere: H$\alpha$ linewidth and mm continua
• Eclipsing Binary Science Via the Merging of Transit and Doppler Exoplanet Survey Data - A Case Study With the MARVELS Pilot Project and SuperWASP
• Photometric Calibration of the $[\alpha /$Fe] Element: II. Calibration with SDSS Photometry
• Photometric Calibration of the [$\alpha$/Fe] Element: I. Calibration with UBV Photometry
• EMISSA: Exploring millimetre indicators of solar-stellar activity III. Comparison of Ca II indices and millimetre continua in a 3D model atmosphere
• StelNet: Hierarchical Neural Network for Automatic Inference in Stellar Characterization