J/A+A/501/687 Evolutionary models for solar twins (do Nascimento+, 2009)
Age and mass of solar twins constrained by lithium abundance.
do Nascimento J.D.Jr, Castro M., Melendenz J., Bazot M., Theado S.,
Porto de Mello G.F., De Medeiros J.R.
<Astron. Astrophys. 501, 687 (2009)>
=2009A&A...501..687D 2009A&A...501..687D
ADC_Keywords: Abundances ; HR diagrams ; Models, evolutionary ; Stars, ages ;
Stars, masses
Keywords: stars: fundamental parameters - stars: horizontal-branch -
stars: abundances - stars: evolution - stars: interiors -
Sun: fundamental parameters
Abstract:
We analyze the non-standard mixing history of the solar twins
HIP 55459, HIP 79672, HIP 56948, HIP 73815, and HIP 100963, to
determine as precisely as possible their mass and age. We computed
a grid of evolutionary models with non-standard mixing at several
metallicities with the Toulouse-Geneva code for a range of stellar
masses assuming an error bar of ±50K in Teff. We choose the
evolutionary model that reproduces accurately the observed low
lithium abundances observed in the solar twins. Our best-fit model for
each solar twin provides a mass and age solution constrained by their
Li content and Teff determination. HIP 56 948 is the most likely
solar-twin candidate at the present time and our analysis infers a
mass of 0.994±0.004M☉ and an age of 4.71±1.39Gyr.
Non-standard mixing is required to explain the low Li abundances
observed in solar twins. Li depletion due to additional mixing in
solar twins is strongly mass dependent. An accurate lithium abundance
measurement and non-standard models provide more precise information
about the age and mass more robustly than determined by classical
methods alone.
Description:
The models are computed by using the Toulouse-Geneva stellar evolution
code TGEC (Hui-Bon-Hoa, 2008, Ap&SS, 316, 55). Details of the physics
of these models can be found in Richard et al. (1996A&A...312.1000R 1996A&A...312.1000R,
2004, SoPh, 220, 243), do Nascimento et al. (2000A&A...357..931D 2000A&A...357..931D), and
Hui-Bon-Hoa (2008, Ap&SS, 316, 55). We computed evolutionary models of
different masses from the zero-age main sequence (ZAMS) to the end of
the hydrogen exhaustion in the core. The calibration method of the
models is based on the Richard et al. (1996A&A...312.1000R 1996A&A...312.1000R)
prescription.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
models.dat 65 27339 Model for 27 initial masses and 8 initial
metallicities
params.dat 64 36 Parameters of each model
mod/* . 36 Original files (one by initial mass and [Fe/H])
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Byte-by-byte Description of file: params.dat
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Bytes Format Units Label Explanations
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1- 5 F5.3 solMass Mass [0.940, 1.044] Initial star mass (G1)
7- 12 F6.3 --- [Fe/H] [-0.002,0.066] Initial metallicity (G2)
14- 26 E13.8 yr tmax Maximal age in model (1)
28- 40 E13.8 --- Li/Li0 Final fraction of lithium abundance (1)
42- 64 A23 --- FileName File name of model, in "mod" subdirectory
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Note (1): from last line of corresponding file
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Byte-by-byte Description of file: models.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 F5.3 solMass Mass Initial star mass (G1)
7- 12 F6.3 --- [Fe/H] Initial metallicity (G2)
14- 17 I4 --- Num Step number
20- 32 E13.8 yr Age Age of the model
34- 41 F8.5 [solLum] logL logarithm of the ratio luminosity of the model
over solar luminosity
44- 50 F7.5 [K] logTeff logarithm of the effective temperature
53- 65 E13.8 --- Li/Li0 Fraction of lithium abundance according to
the initial abundance
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Byte-by-byte Description of file: mod/*
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Bytes Format Units Label Explanations
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1- 4 I4 --- Num Step number
7- 19 E13.8 yr Age Age of the model
21- 28 F8.5 [solLum] logL logarithm of the ratio luminosity of the model
over solar luminosity
31- 37 F7.5 [K] logTeff logarithm of the effective temperature
40- 52 E13.8 --- Li/Li0 Fraction of lithium abundance according to
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Global Notes:
Note (G1): Initial star masses are
0.960, 0.961, 0.969, 0.987, 0.989, 0.990, 0.992, 0.994, 0.995, 0.997,
0.998, 1.000, 1.001, 1.002, 1.004, 1.007, 1.008, 1.010, 1.012, 1.013,
1.015, 1.018, 1.019, 1.021, 1.025, 1.035 and 1.044
Note (G2): Initial metallicities are
-0.002, 0.000, 0.010, 0.020, 0.030, 0.039, 0.040 and 0.066
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Acknowledgements:
do Nascimento J.D., dias(at)dfte.ufrn.br
(End) Matthieu Castro [DFTE, Brasil], Patricia Vannier [CDS] 15-May-2009