J/A+A/615/A172 alpha Cen A and B chemical composition (Morel, 2018)
The chemical composition of alpha Cen AB revisited.
Morel T.
<Astron. Astrophys. 615, A172 (2018)>
=2018A&A...615A.172M 2018A&A...615A.172M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple - Stars, G-type ; Equivalent widths
Keywords: stars: fundamental parameters - stars: abundances -
stars: individual: alpha Cen A - stars: individual: alpha Cen B
Abstract:
The two solar-like stars alpha Cen A and B have long served as
cornerstones for stellar physics in virtue of their immediate
proximity, association in a visual binary, and masses that bracket the
solar one. The recent detection of a terrestrial planet in the cool,
suspected tertiary Proxima Cen now makes the system also of prime
interest in the context of planetary studies. It is therefore of
fundamental importance to tightly constrain the properties of the
individual stellar components. We present a fully self-consistent,
line-by-line differential abundance analysis of alpha Cen AB based on
high-quality HARPS data. Various line lists are used and analysis
strategies implemented to improve the reliability of the results.
Abundances of 21 species with a typical precision of 0.02-0.03dex are
reported. We find that the chemical composition of the two stars is
not scaled solar (e.g., Na and Ni excess, depletion of neutron-capture
elements), but that their patterns are strikingly similar, with a mean
abundance difference (A-B) with respect to hydrogen of
-0.01±0.04dex. Much of the scatter may be ascribed to physical
effects that are not fully removed through a differential analysis
because of the mismatch in parameters between the two components. We
derive an age for the system from abundance indicators (e.g., [Y/Mg]
and [Y/Al]) that is slightly larger than solar and in agreement with
most asteroseismic results. Assuming coeval formation for the three
components belonging to the system, this implies an age of about
∼6Gyrs for the M dwarf hosting the terrestrial planet Proxima Cen b.
After correction for Galactic chemical evolution effects, we find a
trend between the abundance ratios and condensation temperature in
alpha Cen A akin to that of the Sun. However, taking this finding as
evidence for the sequestration of rocky material locked up in planets
may be premature given that a clear link between the two phenomena
remains to be established. The similarity between the abundance
pattern of the binary components argues against the swallowing of a
massive planet by one of the stars after the convective zones have
shrunk to their present-day sizes.
Description:
Lines selected and equivalent width measurements.
"FlagHFS" indicates whether hyperfine structure effects were taken
into account (Y) or not (N).
A line was excluded from the analysis if, in the star or in the Sun,
it was too strong, affected by telluric features, or not adequately
fit by a Gaussian profile (see Sect.4.1). Lines yielding discrepant
abundances were also not considered further.
Objects:
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RA (2000) DE Designation(s)
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14 39 36.49 -60 50 02.4 alpha Cen A = HR 5459
14 39 35.06 -60 50 15.1 alpha Cen B = HR 5460
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 136 446 Lines selected and EW measurements
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See also:
J/A+A/328/261 : Spectroscopy of alpha Cen (Neuforge-Verheecke+ 1997)
J/A+A/406/L23 : Solar-like oscillations in alpha Cen B (Carrier+, 2003)
J/A+A/415/331 : HST/STIS spectra of alpha Cen A (Pagano+, 2004)
J/A+A/597/A137 : HD 123999 and alpha Cen A and B OIFITS files (Kervella+, 2017
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Ion Ion designation
6- 12 F7.3 nm lambda Line wavelength
14 A1 --- FlagHFS [Y/N] Flag hyperfine structure (1)
16- 20 F5.3 eV LEP Lower excitation potential
22- 26 F5.1 0.1pm EWSun Equivalent width for Sun
28- 32 F5.1 0.1pm EWalfCenA ? Equivalent width for alpha Cen A
34- 81 A48 --- r_EWalfCenA ? Line lists including feature for
alpha Cen A (2)
83- 87 F5.1 0.1pm EWalfCenB ? Equivalent width for alpha Cen B
89-136 A48 --- r_EWalfCenB ? Line lists including feature for
alpha Cen B (2)
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Note (1): indicates whether hyperfine structure effects were taken into
account (Y) or not (N).
Note (2): Line lists including feature reference as follows:
Be14 = Bensby et al. (2014A&A...562A..71B 2014A&A...562A..71B, Cat. J/A+A/565/A71)
Bi12 = Biazzo et al. (2012MNRAS.427.2905B 2012MNRAS.427.2905B)
C00 = Chen et al. (2000A&AS..141..491C 2000A&AS..141..491C, Cat. J/A+AS/141/491)
FG01 = Feltzing & Gonzalez (2001A&A...367..253F 2001A&A...367..253F)
J14 = Jofre et al. (2014A&A...564A.133J 2014A&A...564A.133J, Cat. J/A+A/564/A133)
J15 = Jofre et al. (2015A&A...582A..81J 2015A&A...582A..81J, Cat. J/A+A/582/A81)
Me14 = Melendez et al. (2014, Cat. J/ApJ/791/14)
Mo14 = Morel et al. (2014A&A...564A.119M 2014A&A...564A.119M, Cat. J/A+A/564/A119)
R03 = Reddy et al. (2003MNRAS.340..304R 2003MNRAS.340..304R, Cat. J/MNRAS/340/304)
S08 = Sousa et al. (2008A&A...487..373S 2008A&A...487..373S, Cat. J/A+A/487/373)
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Acknowledgements:
Thierry Morel, morel(at)astro.ulg.ac.be
(End) Patricia Vannier [CDS] 30-Apr-2018