J/A+A/618/A16 A(Li) and 6Li/7Li 3D NLTE corrections (Harutyunyan+, 2018)
3D non-LTE corrections for Li abundance and 6Li/7Li isotopic ratio in
solar-type stars. I. Application to HD 207129 and HD 95456.
Harutyunyan G., Steffen M., Mott A., Caffau E., Israelian G.,
Gonzalez Hernandez J.I., Strassmeier K.G.
<Astron. Astrophys. 618, A16 (2018)>
=2018A&A...618A..16H 2018A&A...618A..16H (SIMBAD/NED BibCode)
ADC_Keywords: Spectroscopy; Abundances; Models, atmosphere; Line Profiles
Keywords: stars: abundances - stars: atmospheres - radiative transfer -
line: formation - line: profiles
Abstract:
The purpose of this work is to provide corrections for the lithium
abundance, A(Li), and the 6Li/7Li ratio that can easily be applied
to correct 1D LTE lithium abundances in G and F dwarf stars of
approximately solar mass and metallicity for three-dimensional (3D)
and non-LTE (NLTE) effects. The corrections for A(Li) and 6Li/7Li
are computed using grids of 3D NLTE and 1D LTE synthetic lithium line
profiles, generated from 3D hydro-dynamical CO5BOLD and 1D hydrostatic
LHD model atmospheres, respectively. For comparative purposes, all
calculations are performed for three different line lists representing
the LiI 670.8nm spectral region. The 3D NLTE corrections are then
approximated by analytical expressions as a function of the stellar
parameters (Teff, logg, [Fe/H], vsini, A(Li), 6Li/7Li).
The derived 3D NLTE corrections range between -0.01 and +0.11dex for
A(Li), and between -4.9 and -0.4% for the 6Li/7Li ratio, depending
on the adopted stellar parameters. Our findings show a general
consistency with recent works on lithium abundance corrections. In the
case of the 6Li/7Li ratio, our corrections are always negative,
showing that 1D LTE analysis can significantly overestimate the
presence of 6Li (up to 4.9 percentage points) in the atmospheres of
solar-like dwarf stars. These results emphasize the importance of
reliable 3D model atmospheres combined with NLTE line formation for
deriving precise isotopic lithium abundances. Although 3D NLTE
spectral synthesis implies an extensive computational effort, the
results can be made accessible with parametric tools like the ones
presented in this work.
Description:
A grid of 3D non-LTE (NLTE) corrections for the lithium abundance,
A(Li), and the 6Li/7Li isotopic ratio are presented. These
corrections can be easily applied to correct 1D LTE lithium abundances
in G and F dwarf stars of approximately solar mass and metallicity for
3D and NLTE effects. The stellar parameters defining the grid are
effective temperatures, Teff (5900, 6300 and 6500K), surface gravity,
logg (4.0 and 4.5), metallicity, [Fe/H] (-1.0, -0.5, 0.0, +0.5), 1D
LTE lithium abundance, A(Li) (1.5, 2.0, 2.5), 1D LTE 6Li/7Li
isotopic ratio (0, 5 and 10%), as well as projected rotational
velocity, vsini (0, 2, 4 and 6km/s). Based on this table, a web page
calculator was created that allows to compute the 3D NLTE corrections
of A(Li) and 6Li/7Li ratio for a given combination of stellar
parameters (https://pages.aip.de/li67nlte3d/).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 36 864 3D NLTE corrections of A(Li) and 6Li/7Li
isotopic ratio for solar-type stars
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Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 4 I4 K Teff Effective temperature
6- 8 F3.1 [cm/s2] logg Surface gravity
10- 13 F4.1 [-] [Fe/H] Metallicity
15- 17 F3.1 [-] A(Li) 1D LTE lithium abundance
19- 20 I2 % 6Li/7Li 1D LTE 6Li/7Li isotopic ratio
22 I1 km/s vsini Projected rotational velocity
24- 29 F6.3 [-] D(A(Li)) 3D NLTE correction of A(Li), Δ(A(Li))
31- 36 F6.3 % D(6Li/7Li) 3D NLTE correction of 6Li/7Li ratio,
Δ(6Li/7Li)
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Acknowledgements:
Gohar Harutyunyan, gharutyunyan(at)aip.de
(End) Gohar Harutyunyan [AIP, Germany], Patricia Vannier [CDS] 11-Jul-2018