The chemical composition of $\alpha$ Cen AB revisited

Abstract

We present a fully self-consistent, line-by-line differential abundance analysis of $\alpha$ Cen AB based on high-quality HARPS data. Various line lists are used and analysis strategies implemented to improve the reliability of the results. Abundances of 21 species with a typical precision of 0.02-0.03 dex are reported. We find that the chemical composition of the two stars is not scaled solar (e.g. Na and Ni excess, depletion of neutron-capture elements), but that their patterns are strikingly similar, with a mean abundance difference (A - B) with respect to hydrogen of -0.01$\pm$0.04 dex. Much of the scatter may be ascribed to physical effects that are not fully removed through a differential analysis because of the mismatch in parameters between the two components. We derive an age for the system from abundance indicators (e.g. [Y/Mg] and [Y/Al]) that is slightly larger than solar and in agreement with most asteroseismic results. Assuming coeval formation for the three components belonging to the system, this implies an age of about $\sim$6 Gyrs for the M dwarf hosting the terrestrial planet Proxima Cen b. After correction for Galactic chemical evolution effects, we find a trend between the abundance ratios and condensation temperature in $\alpha$ Cen A akin to that of the Sun. However, taking this finding as evidence for the sequestration of rocky material locked up in planets may be premature given that a clear link between the two phenomena remains to be established. The similarity between the abundance pattern of the binary components argues against the swallowing of a massive planet by one of the stars after the convective zones have shrunk to their present-day sizes.

Accepted for publication in A&A. 24 pages, 8 figures. Abstract abridged

References in corpus (64)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• A terrestrial planet candidate in a temperate orbit around Proxima Centauri
• New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey
• Most 1.6 Earth-Radius Planets are not Rocky
• Spectroscopic parameters for 451 stars in the HARPS GTO planet search program. Stellar [Fe/H] and the frequency of exo-Neptunes
• Determining stellar atmospheric parameters and chemical abundances of FGK stars with iSpec
• Standing on the shoulders of Dwarfs: the Kepler asteroseismic LEGACY sample II - radii, masses, and ages
• Galactic Chemical Evolution and solar s-process abundances: dependence on the 13C-pocket structure
• Proxima's orbit around Alpha Centauri
• High-precision abundances of elements in solar twin stars: Trends with stellar age and elemental condensation temperature
• Standing on the shoulders of Dwarfs: the $Kepler$ asteroseismic LEGACY sample I - oscillation mode parameters
• Gaia-ESO Survey: The analysis of high-resolution UVES spectra of FGK-type stars
• NLTE abundances of Mn in a sample of metal-poor stars
• Oxygen Abundances in Nearby Stars. Clues to the formation and evolution of the Galactic disk
• Calibrating Gyrochronology using Kepler Asteroseismic targets
• Steady-state planet migration by the Kozai-Lidov mechanism in stellar binaries
• The amplitude of solar oscillations using stellar techniques
• Non-LTE aluminium abundances in late-type stars
• The Gaia FGK Benchmark Stars - High resolution spectral library
• Stellar Chemical Abundances: In Pursuit of the Highest Achievable Precision
• 18 Sco: a solar twin rich in refractory and neutron-capture elements. Implications for chemical tagging
• Metallicity of M dwarfs IV. A high-precision [Fe/H] and Teff technique from high-resolution optical spectra for M dwarfs
• On the origin of stars with and without planets. Tc trends and clues to Galactic evolution
• Stellar parameters of early M dwarfs from ratios of spectral features at optical wavelengths
• The Rich Are Different: Evidence from the RAVE Survey for Stellar Radial Migration
• High-precision abundances of Sc, Mn, Cu, and Ba in solar twins. Trends of element ratios with stellar age
• The chemical compositions of solar twins in the open cluster M67
• High precision abundances in the 16 Cyg binary system: a signature of the rocky core in the giant planet
• Planet formation in Alpha Centauri A revisited: not so accretion-friendly after all
• A high precision chemical abundance analysis of the HAT-P-1 stellar binary: constraints on planet formation
• On the metallicity dependance of the [Y/Mg] - age relation for solar type stars
• The radii and limb darkenings of Alpha Centauri A and B - Interferometric measurements with VLTI/PIONIER
• Formation and Detectability of Terrestrial Planets Around Alpha Centauri B
• High-precision abundances of elements in Kepler LEGACY stars. Verification of trends with stellar age
• A large sample of calibration stars for Gaia: log g from Kepler and CoRoT
• The Alpha Centauri Binary System: Atmospheric Parameters and Element Abundances
• Abundance Differences Between Exoplanet Binary Host Stars XO-2N and XO-2S -- Dependence on Stellar Parameters
• What are little worlds made of? Stellar abundances and the building blocks of planets
• The Gaia-ESO Survey: calibration strategy
• Red Supergiant Stars as Cosmic Abundance Probes. III. NLTE effects in J-band Magnesium lines
• Detailed Abundances of Planet-Hosting Wide Binaries. I. Did Planet Formation Imprint Chemical Signatures in the Atmospheres of HD 20782/81?
• Signatures of rocky planet engulfment in HAT-P-4. Implications for chemical tagging studies
• Influence of inelastic collisions with hydrogen atoms on the non-LTE modelling of Ca I and Ca II lines in late-type stars
• C/O vs Mg/Si ratios in solar type stars: The HARPS sample
• Close stellar conjunctions of alpha Centauri A and B until 2050 - An mK = 7.8 star may enter the Einstein ring of alpha Cen A in 2028
• Hubble Space Telescope search for the transit of the Earth-mass exoplanet Alpha Centauri Bb
• The Changing Face of $\alpha$ Centauri B: Probing plage and stellar activity in K-dwarfs
• ALMA Discovery of Dust Belts Around Proxima Centauri
• Atmospheric parameters and chemical properties of red giants in the CoRoT asteroseismology fields
• The Magellan PFS Planet Search Program: Radial Velocity and Stellar Abundance Analyses of the 360 AU, Metal-Poor Binary "Twins" HD 133131A & B
• Possible Internal Structures and Compositions of Proxima Centauri b
• The [Y/Mg] clock works for evolved solar metallicity stars
• Planet Detectability in the Alpha Centauri System
• Detailed chemical compositions of the wide binary HD 80606/80607: revised stellar properties and constraints on planet formation
• Proxima Centauri reloaded: Unravelling the stellar noise in radial velocities
• Long-Term Stability of Tightly Packed Multi-Planet Systems in Prograde, Coplanar, Circumstellar Orbits within the $\alpha$ Centauri AB System
• Precise radial velocities of giant stars IX. HD 59686 Ab: a massive circumstellar planet orbiting a giant star in a ~13.6 au eccentric binary system
• The Mt John University Observatory Search For Earth-mass Planets In The Habitable Zone Of Alpha Centauri
• Flare activity and photospheric analysis of Proxima Centauri
• Was Proxima captured by alpha Centauri A and B?
• Implications of the spectroscopic abundances in α Centauri A and B
• A Multi-Year Search For Transits Of Proxima Centauri. I: Light Curves Corresponding To Published Ephemerides
• Effects of Proxima Centauri on Planet Formation in Alpha Centauri

Cited by in corpus (16)

• Accuracy and precision of industrial stellar abundances
• The 10 parsec sample in the Gaia era
• High-precision stellar abundances of the elements - methods and applications
• Age dating of an early Milky Way merger via asteroseismology of the naked-eye star $\nu$ Indi
• EvryFlare III: Temperature Evolution and Habitability Impacts of Dozens of Superflares Observed Simultaneously by Evryscope and TESS
• Flaring activity of Proxima Centauri from TESS observations: quasi-periodic oscillations during flare decay and inferences on the habitability of Proxima b
• Reinvestigating $\alpha$ Cen AB in light of asteroseismic forward and inverse methods
• HAZMAT VI: The Evolution of Extreme Ultraviolet Radiation Emitted from Early M Star
• Measuring precise radial velocities on individual spectral lines. III. Dependence of stellar activity signal on line formation temperature
• A blue depression in the optical spectra of M dwarfs
• Precision Millimeter Astrometry of the $\alpha$ Centauri AB System
• Extending the FIP bias sample to magnetically active stars. Challenging the FIP bias paradigm?
• Asteroseismology and Spectropolarimetry of the Exoplanet Host Star $\lambda$ Serpentis
• Water content trends in K2-138 and other low-mass multiplanetary systems
• Testing abundance-age relations beyond solar analogues with Kepler LEGACY stars
• Europium as a lodestar: diagnosis of radiogenic heat production in terrestrial exoplanets