Lithium abundance and 6Li/7Li ratio in the active giant HD123351 I. A comparative analysis of 3D and 1D NLTE line-profile fits

Abstract

Current three-dimensional (3D) hydrodynamical model atmospheres together with NLTE spectrum synthesis, permit to derive reliable atomic and isotopic chemical abundances from high-resolution stellar spectra. Not much is known about the presence of the fragile 6Li isotope in evolved solar-metallicity RGB stars, not to mention its production in magnetically active targets like HD123351. From fits of the observed CFHT spectrum with synthetic line profiles based on 1D and 3D model atmospheres, we seek to estimate the abundance of the 6Li isotope and to place constraints on its origin. We derive A(Li) and the 6Li/7Li isotopic ratio by fitting different synthetic spectra to the Li-line region of a high-resolution CFHT spectrum (R=120 000, S/R=400). The synthetic spectra are computed with four different line lists, using in parallel 3D hydrodynamical CO5BOLD and 1D LHD model atmospheres and treating the line formation of the lithium components in non-LTE (NLTE). We find A(Li)=1.69+/-0.11 dex and 6Li/7Li=8.0+/-4.4 % in 3D-NLTE, using the line list of Meléndez et al. (2012), updated with new atomic data for V I, which results in the best fit of the lithium line profile of HD123351. Two other line lists lead to similar results but with inferior fit qualities. Our 2-sigma detection of the 6Li isotope is the result of a careful statistical analysis and the visual inspection of each achieved fit. Since the presence of a significant amount of 6Li in the atmosphere of a cool evolved star is not expected in the framework of standard stellar evolution theory, non-standard, external lithium production mechanisms, possibly related to stellar activity or a recent accretion of rocky material, need to be invoked to explain the detection of 6Li in HD123351.

16 pages, 11 figures. Accepted for publication in A&A

References in corpus (6)

• YREC: The Yale Rotating Stellar Evolution Code
• Line shift, line asymmetry, and the 6Li/7Li isotopic ratio determination
• The forbidden 1082 nm line of sulphur: the photospheric abundance of sulphur in the Sun and 3D effects
• The Solar Twin Planet Search. V. Close-in, low-mass planet candidates and evidence of planet accretion in the solar twin HIP 68468
• Is 6-Li in metal-poor halo stars produced in situ by solar-like flares?
• High Dispersion Spectroscopy of Solar-type Superflare Stars. III. Lithium Abundances

Cited by in corpus (21)

• The chemical make-up of the Sun: A 2020 vision
• 3D NLTE spectral line formation of lithium in late-type stars
• PEPSI deep spectra. I. The Sun-as-a-star
• Observational constraints on the origin of the elements II. 3D non-LTE formation of Ba ii lines in the solar atmosphere
• The GAPS Programme with HARPS-N at TNG. XXXV. Fundamental properties of transiting exoplanet host stars
• 3D non-LTE corrections for Li abundance and 6Li/7Li isotopic ratio in solar-type stars I. Application to HD 207129 and HD 95456
• The Active Chromospheres of Lithium-Rich Red Giant Stars
• Improving spectroscopic lithium abundances. Fitting functions for 3D non-LTE corrections in FGK stars of different metallicity
• The ${}^6$Li/${}^7$Li isotopic ratio in the metal-poor binary CS22876--032
• Antisolar differential rotation with surface lithium enrichment on the single K-giant V1192 Orionis
• An extended and refined grid of 3D STAGGER model atmospheres. Processed snapshots for stellar spectroscopy
• Comparative study of the direct $\alpha +d$ $\to$ ${}^6$Li + $\gamma$ astrophysical capture reaction in few-body models
• A detailed study of Lithium in 107 CHEPS dwarf stars
• Internal Gravity Waves in the Magnetized Solar Atmosphere. II. Energy Transport
• On Lithium-6 as diagnostic of the lithium-enrichment mechanism in red giants
• The discovery of a Li-Na-rich giant star in Omega Centauri: formed from the pure ejecta of super-AGB stars?
• The ups and downs of inferred cosmological lithium
• VPNEP: Detailed characterization of TESS targets around the Northern Ecliptic Pole
• Influence of orthogonalization procedure on astrophysical S-factor for the direct $\alpha +d$ $\to$ ${}^6$Li + $\gamma$ capture process in a three-body model
• Study of the ${}^7$Be($d$,${}^3$He)${}^6$Li* reaction at 5 MeV/u
• On the lithium abundance of the visual binary components $\xi$ Boo A (G8V) and $\xi$ Boo B (K5V)