J/A+A/655/A99 Chemical abundances of 762 FGK stars (Delgado Mena+, 2021)
Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program
IV. Carbon and C/O ratios for Galactic stellar populations and planet hosts.
Delgado Mena E., Adibekyan V.Zh., Santos N.C., Tsantaki M.,
Gonzalez Hernandez J.I., Sousa S.G., Bertran de Lis S.
<Astron. Astrophys. 655, A99 (2021)>
=2021A&A...655A..99D 2021A&A...655A..99D (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, nearby ; Exoplanets ; Abundances
Keywords: stars: abundances - stars: fundamental parameters -
Galaxy: evolution - Galaxy: disk - planetary systems -
planets and satellites: composition
Abstract:
To understand the formation and composition of planetary systems, it
is essential to have insights into the chemical composition of their
host stars. In particular, C/O elemental ratios are useful for
constraining the density and bulk composition of terrestrial planets.
We study the carbon abundances with a twofold objective. On the one
hand, we want to evaluate the behaviour of carbon in the context of
Galactic chemical evolution. On the other hand, we focus on the
possible dependence of carbon abundances on the presence of planets
and on the impact of various factors (such as different oxygen lines)
on the determination of C/O elemental ratios.
We derived chemical abundances of carbon from two atomic lines for 757
FGK stars in the HARPS-GTO sample, observed with high-resolution
(R∼115000) and high-quality spectra. The abundances were derived using
a standard Local Thermodinamyc Equilibrium analysis with automatically
measured Equivalent Widths injected into the code MOOG and a grid of
Kurucz ATLAS9 atmospheres. Oxygen abundances, derived using different
lines, were taken from previous papers in this series and updated with
the new stellar parameters.
We find that thick- and thin-disk stars are chemically disjunct for
[C/Fe] across the full metallicity range that they have in common.
Moreover, the population of high-α metal-rich stars also
presents higher and clearly separated [C/Fe] ratios than thin-disk
stars up to [Fe/H]∼0.2dex. The [C/O] ratios present a general flat
trend as a function of [O/H] but becomes negative at [O/H]≳0dex. This
trend is more clear when considering stars of similar metallicity. We
find tentative evidence that stars with low-mass planets at lower
metallicities have higher [C/Fe] ratios than stars without planets at
the same metallicity, in the same way as has previously been found for
α elements. Finally, the elemental C/O ratios for the vast
majority of our stars are below 0.8 when using the oxygen line at
6158Å however, the forbidden oxygen line at 6300Å provides
systematically higher C/O values (going above 1.2 in a few cases)
which also show a dependence on Teff. Moreover, by using different
atmosphere models the C/O ratios can have a non negligible difference
for cool stars. Therefore, C/O ratios should be scaled to a common
solar reference in order to correctly evaluate its behaviour. We find
no significant differences in the distribution of C/O ratios for the
different populations of planet hosts, except when comparing the stars
without detected planets with the stars hosting Jupiter-type planets.
However, we note that this difference might be caused by the different
metallicity distributions of both populations.
The derivation of homogeneous abundances from high-resolution spectra
in samples that are modest in size is of great utility in constraining
models of Galactic chemical evolution. The combination of these
high-quality data with the long-term study of planetary presence in
our sample is crucial for achieving an accurate understanding of the
impact of stellar chemical composition on planetary formation
mechanisms.
Description:
The file table.dat contains the stellar parameters and chemical
abundances ratios of the sample together with the S/N ratio of the
spectra. The abundance ratios are given with respect to the solar
value.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 95 762 Abundance ratios, errors, planet presence
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See also:
J/A+A/545/A32 : Chemical abundances of 1111 FGK stars (Adibekyan+, 2012)
J/A+A/606/A94 : Chemical abundances of 1059 FGK stars (Delgado Mena+, 2017)
J/A+A/634/A136 : Chemical sulfur abundances of 719 FGK stars
(Costa Silva+, 2020)
Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Star Star's identifier
12- 15 I4 K Teff Effective Temperature
17- 20 F4.2 [cm/s2] logg Surface gravity
22- 26 F5.2 --- [Fe/H] Iron abundance
28- 31 I4 --- S/N Signal to noise ratio
33- 38 F6.3 [Sun] [C/Fe] ?=9.999 Abundance [C/Fe]
40- 44 F5.3 [Sun] e_[C/Fe] ?=9.999 Error of [C/Fe]
46- 51 F6.3 [Sun] [O1/Fe] ?=9.999 Abundance [O/Fe] from 6158Å line
53- 57 F5.3 [Sun] e_[O1/Fe] ?=9.999 Error of [O/Fe] from 6158Å line
59- 64 F6.3 [Sun] [O2/Fe] ?=9.999 Abundance [O/Fe] from 6300Å line
66- 70 F5.3 [Sun] e_[O2/Fe] ?=9.999 Error of [O/Fe] from 6300Å line
72- 77 F6.3 [Sun] [C/O1] ?=9.999 Ratio [C/O] using 6158Å line
79- 84 F6.3 [Sun] [C/O2] ?=9.999 Ratio [C/O] using 6300Å line
86- 89 A4 --- planet Type of the most massive planet present
(jup, nept or non)
91- 95 A5 --- pop Galactic population
(thick, thin, halo or hamr)
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Acknowledgements:
Elisa Delgado Mena, elisa.delgado(at)astro.up.pt
References:
Adibekyan et al., Paper I 2012A&A...545A..32A 2012A&A...545A..32A, Cat. J/A+A/545/32
Delgado Mena et al., Paper II 2017A&A...606A..94D 2017A&A...606A..94D, Cat. J/A+A/606/A94
Costa Silva et al., Paper III 2020A&A...634A.136C 2020A&A...634A.136C, Cat. J/A+A/634/136
(End) Elisa Delgado Mena [IA, Portugal], Patricia Vannier [CDS] 17-Sep-2021