HD 80606: searching for the chemical signature of planet formation

SAFFE, C.; FLORES TRIVIGNO, M.; BUCCINO, A. P.

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2015 vol. 582 p. 17 - 34

0004-6361

Context. Binary systems with similar components are ideal laboratoriesthat allow several physical processes to be tested, such as the possiblechemical pattern imprinted by the planet formation process. Aims:We explore the probable chemical signature of planet formation in theremarkable binary system HD 80606-HD 80607. The star HD 80606 hosts agiant planet with ~4 MJup detected by both transit and radialvelocity techniques, which is one of the most eccentric planets detectedto date. We study condensation temperature Tc trends ofvolatile and refractory element abundances to determine whether there isa depletion of refractories, which could be related to the terrestrialplanet formation. Methods: We carried out a high-precisionabundance determination in both components of the binary system via aline-by-line, strictly differential approach. First, we used the Sun asa reference and then we used HD 80606. The stellar parametersTeff, log g, [Fe/H] and vturb were determined byimposing differential ionization and excitation equilibrium of Fe I andFe II lines, with an updated version of the program FUNDPAR, togetherwith plane-parallel local thermodynamic equilibrium (LTE) ATLAS9 modelatmospheres and the MOOG code. Then, we derived detailed abundances of24 different species with equivalent widths and spectral synthesis withthe program MOOG. The chemical patterns were compared with thesolar-twins Tc trends of Meléndez et al. (2009, AJ,704, L66) and with a sample of solar-analogue stars with [Fe/H] ~ +0.2dex from Neves et al. (2009, A&A, 497, 563). The Tctrends were also compared mutually between both stars of the binarysystem. Results: From the study of Tc trends, weconcluded that the stars HD 80606 and HD 80607 do not seem to bedepleted in refractory elements, which is different for the case of theSun. Then, following the interpretation of Meléndez et al.(2009), the terrestrial planet formation would have been less efficientin the components of this binary system than in the Sun. The lack of atrend in refractory elements with Tc between both starsimplies that the presence of a giant planet do not neccesarily imprint achemical signature in their host stars, similar to the recent result ofLiu et al. (2014, MNRAS, 442, L51). This is also in agreement withMeléndez et al. (2009), who suggest that the presence of close-ingiant planets might prevent the formation of terrestrial planets.Finally, we speculate about a possible, ejected or non-detected, planetaround the star HD 80607