ELEMENTAL ABUNDANCE DIFFERENCES IN THE 16 CYGNI BINARY SYSTEM: A SIGNATURE OF GAS GIANT PLANET FORMATION?

Author(s)

Ramirez, I. ^[1] ; Melendez, J. ^[2] ; Cornejo, D. ^[3] ; Roederer, I. U. ^[1] ; Fish, J. R. ^{[1, 4]}

Affiliation

^[1] Observ Carnegie Inst Sci, Pasadena, CA 91101 - USA

^[2] Univ Sao Paulo, Dept Astron IAG USP, BR-05508900 Sao Paulo - Brazil

^[3] Agencia Espacial Peru CONIDA, Dept Astrofis, Lima - Peru

^[4] Harvey Mudd Coll, Claremont, CA 91711 - USA

• Document type: Journal article
• Source: ASTROPHYSICAL JOURNAL; v. 740, n. 2 OCT 20 2011.
• Web of Science Citations: 62

Abstract

The atmospheric parameters of the components of the 16 Cygni binary system, in which the secondary has a gas giant planet detected, are measured accurately using high-quality observational data. Abundances relative to solar are obtained for 25 elements with a mean error of sigma({[}X/H]) = 0.023 dex. The fact that 16 Cyg A has about four times more lithium than 16 Cyg B is normal considering the slightly different masses of the stars. The abundance patterns of 16 Cyg A and B, relative to iron, are typical of that observed inmost of the so-called solar twin stars, with the exception of the heavy elements (Z > 30), which can, however, be explained by Galactic chemical evolution. Differential (A-B) abundances are measured with even higher precision (sigma(Delta{[}X/H]) = 0.018 dex, on average). We find that 16 Cyg A is more metal-rich than 16 Cyg B by Delta{[}M/H] = +0.041 +/- 0.007 dex. On an element-to-element basis, no correlation between the A-B abundance differences and dust condensation temperature (T(C)) is detected. Based on these results, we conclude that if the process of planet formation around 16 Cyg B is responsible for the observed abundance pattern, the formation of gas giants produces a constant downward shift in the photospheric abundance of metals, without a T(C) correlation. The latter would be produced by the formation of terrestrial planets instead, as suggested by other recent works on precise elemental abundances. Nevertheless, a scenario consistent with these observations requires the convective envelopes of similar or equal to 1 M(circle dot) stars to reach their present-day sizes about three times quicker than predicted by standard stellar evolution models. (AU)

• FAPESP's process: 10/17510-3 - Influence of planet formation in the chemical composition of solar type stars
• Grantee: Jorge Luis Melendez Moreno
• Support Opportunities: Regular Research Grants