2018A&A...615A.172M


Query : 2018A&A...615A.172M

2018A&A...615A.172M - Astronomy and Astrophysics, volume 615A, 172-172 (2018/7-1)

The chemical composition of α Centauri AB revisited.

MOREL T.

Abstract (from CDS):

The two solar-like stars α 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 that of the Sun. 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 α 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 α 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.

Abstract Copyright: © ESO 2018

Journal keyword(s): stars: fundamental parameters - stars: abundances - stars: individual: α Cen A - stars: individual: α Cen B

VizieR on-line data: <Available at CDS (J/A+A/615/A172): tablea1.dat>

Simbad objects: 15

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Number of rows : 15
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 HD 20781 PM* 03 20 02.9428582501 -28 47 01.790465531   9.263 8.44 8.17 8.43 G9.5V 114 1
2 HD 20782 PM* 03 20 03.5777546706 -28 51 14.660358176   8.03 7.38     G1.5V 208 1
3 BD+50 1471 PM* 07 48 06.4723053776 +50 13 32.920598923   12.002 11.138 10.669 10.243 G9V 172 1
4 HD 80606 PM* 09 22 37.5768032712 +50 36 13.435326684   9.78 9.00     G8V 328 2
5 HD 80607 PM* 09 22 39.7366541424 +50 36 13.952919312   9.937 9.070     G5 100 2
6 NAME Proxima Centauri Er* 14 29 42.9461331854 -62 40 46.164680672 14.21 12.95 11.13 9.45 7.41 M5.5Ve 1281 0
7 * alf Cen B PM* 14 39 35.06311 -60 50 15.0992 2.89 2.21 1.33     K1V 1015 2
8 * alf Cen A SB* 14 39 36.49400 -60 50 02.3737 0.96 0.72 0.01     G2V 1270 1
9 * alf Cen ** 14 39 40.4 -60 50 20   0.4 -0.1     G2V+K1V 948 0
10 HD 133131 ** 15 03 35.80651 -27 50 27.5520           G2V+G2V 46 0
11 BD+36 2593 * 15 19 57.9203617176 +36 13 46.738078788   11.83 11.12     F 106 1
12 Kepler-10 Ro* 19 02 43.0613892904 +50 14 28.701617339       11.00   G2V 200 1
13 * 16 Cyg ** 19 41 49.09 +50 31 31.6           ~ 149 0
14 CD-34 14724A EB* 20 55 07.9443524136 -34 08 08.007489384   10.74 10.05 10.17 9.774 F8 68 0
15 BD+37 4734B PM* 22 57 46.8442481880 +38 40 30.358351704   10.82 9.87     G0V 165 1

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