J/A+A/640/A81 Abundances of 72 solar-type stars (Nissen+, 2020)
High-precision abundances of elements in solar-type stars.
Evidence of two distinct sequences in abundance-age relations.
Nissen P.E., Christensen-Dalsgaard J., Mosumgaard J.R., Silva Aguirre V.,
Spitoni E., Verma K.
<Astron. Astrophys. 640, A81 (2020)>
=2020A&A...640A..81N 2020A&A...640A..81N (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, G-type ; Abundances
Keywords: stars: solar-type - stars: fundamental parameters -
stars: abundances - Galaxy: disk - Galaxy: evolution
Abstract:
Previous high-precision studies of abundances of elements in solar
twin stars are extended to a wider metallicity range to see how the
trends of element ratios with stellar age depend on [Fe/H].
HARPS spectra with S/N≳600 at λ∼6000Å were analysed with
MARCS model atmospheres to obtain 1D LTE abundances of C, O, Na, Mg,
Al, Si, Ca, Ti, Cr, Fe, Ni, Sr, and Y in 72 solar-type stars including
the binary star zeta Reticuli and ASTEC stellar models were used to
determine stellar ages from effective temperatures, luminosities
obtained via Gaia DR2 parallaxes, and heavy element abundances.
The age-metallicity distribution appears to consist of the following
two distinct populations: a sequence of old stars with a steep rise of
[Fe/H] to ~+0.3 dex at an age of ∼7Gyr and a younger sequence with
[Fe/H] increasing from about -0.3dex to ~+0.2dex over the last
6Gyr. Furthermore, the trends of several abundance ratios, [O/Fe],
[Na/Fe], [Ca/Fe], and [Ni/Fe], as a function of stellar age, split
into two corresponding sequences. The [Y/Mg]-age relation, on the
other hand, shows no offset between the two age sequences and has no
significant dependence on [Fe/H], but the components of a visual
binary star, ζ Reticuli, have a large and puzzling deviation.
The split of the age-metallicity distribution into two sequences may
be interpreted as evidence of two episodes of accretion of gas onto
the Galactic disk with a quenching of star formation in between. Some
of the [X/Fe]-age relations support this scenario but other relations
are not so easy to explain, which calls for a deeper study of
systematic errors in the derived abundances as a function of [Fe/H],
in particular 3D non-LTE effects.
Description:
Stellar parameters are given in Table 1 and abundance ratios with
respect to Fe in Table 2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 94 72 Stellar parameters
table2.dat 104 72 Abundance ratios
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See also:
J/AJ/105/2299 : Li abundance of solar-type stars. II. (Soderblom+, 1993)
J/A+A/327/587 : Abundances of 9 solar-type stars (Tomkin+ 1997)
J/PASJ/57/65 : CNO abundances of solar-type stars (Takeda+, 2005)
J/A+A/468/663 : Li abundances in solar-analog stars (Takeda+, 2007)
J/A+A/508/L17 : Abundances in solar analogs (Ramirez+, 2009)
J/A+A/515/A93 : Li abundances in solar-analog stars. II. (Takeda+, 2010)
J/ApJ/839/94 : Abundances of solar twins from Keck/HIRES (Bedell+, 2017)
J/ApJ/865/68 : Abundances for 79 Sun-like stars within 100pc (Bedell+, 2018)
J/MNRAS/423/122 : Abundances of 93 solar-type Kepler targets (Bruntt+, 2012)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 I8 --- HD HD number
9- 14 I6 K Teff Effective temperature
15- 22 F8.3 [cm/s2] logg-sp logarithmic spectroscopic gravity
23- 29 F7.2 km/s Vturb Microturbulence parameter
30- 37 F8.3 [Sun] [Fe/H] Logarithmic Fe/H ratio
38- 45 F8.3 [Sun] [alpha/Fe] Logarithmic alpha/Fe ratio
46- 54 F9.4 --- Zs Stellar surface heavy element fraction
55- 62 F8.3 [Sun] logL Logarithmic stellar luminosity
63- 68 F6.1 Gyr Age Stellar age
69- 73 F5.1 Gyr e_Age 1-sigma error of stellar age
74- 80 F7.2 [Sun] Mass Stellar mass
81- 87 F7.3 [cm/s2] logg-ph logarithmic photometric gravity
88- 94 F7.3 --- Ys Stellar surface helium fraction
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 8 I8 --- HD HD number
9- 16 F8.3 [Sun] [C/Fe] Logarithmic C/Fe ratio
17- 24 F8.3 [Sun] [O/Fe] Logarithmic O/Fe ratio
25- 32 F8.3 [Sun] [Na/Fe] Logarithmic Na/Fe ratio
33- 40 F8.3 [Sun] [Mg/Fe] Logarithmic Mg/Fe ratio
41- 48 F8.3 [Sun] [Al/Fe] Logarithmic Al/Fe ratio
49- 56 F8.3 [Sun] [Si/Fe] Logarithmic Si/Fe ratio
57- 64 F8.3 [Sun] [Ca/Fe] Logarithmic Ca/Fe ratio
65- 72 F8.3 [Sun] [Ti/Fe] Logarithmic Ti/Fe ratio
73- 80 F8.3 [Sun] [Cr/Fe] Logarithmic Cr/Fe ratio
81- 88 F8.3 [Sun] [Ni/Fe] Logarithmic Ni/Fe ratio
89- 96 F8.3 [Sun] [Sr/Fe] Logarithmic Ni/Fe ratio
97-104 F8.3 [Sun] [Y/Fe] Logarithmic Y/Fe ratio
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Acknowledgements:
Poul Erik Nissen, pen(at)phys.au.dk
(End) Poul Erik Nissen [Aarhus University], Patricia Vannier [CDS] 18-Jun-2020