Be Abundances In Cool Main-Sequence Stars With Exoplanets

E. Delgado Mena, G. Israelian, J. I. González Hernández, N. C. Santos, R. Rebolo López

Resumo
We present new Ultraviolet and Visual Echelle Spectrograph (UVES) spectra of a sample of 15 cool unevolved stars with and without detected planetary companions. Together with previous determinations, we study Be depletion and possible differences in Be abundances between the two groups of stars. We obtain a final sample of 89 and 40 stars with and without planets, respectively, which covers a wide range of effective temperatures, from 4700 K to 6400 K, and includes several cool dwarf stars for the first time. We determine Be abundances for these stars and find that for most of them (the coolest ones) the Be ii resonance lines are often undetectable, implying significant Be depletion. While for hot stars Be abundances are approximately constant, with a slight fall as T_eff decreases and the Li–Be gap around 6300 K, we find a steep drop of Be content as T_eff decreases for T_eff < 5500 K, confirming the results of previous papers. Therefore, for these stars there is an unknown mechanism destroying Be that is not reflected in current models of Be depletion. Moreover, this strong Be depletion in cool objects takes place for all the stars regardless of the presence of planets; thus, the effect of extra Li depletion in solar-type stars with planets when compared with stars without detected planets does not seem to be present for Be, although the number of stars at those temperatures is still small to reach a final conclusion.

Palavras chave
planetary systems – planets and satellites: formation – stars: abundances – stars: atmospheres – stars: fundamental parameters

Notas
Based on observations made with UVES at VLT Kueyen 8.2 m telescope at the European Southern Observatory (Cerro Paranal, Chile) in program 86.D-0082A.

The Astrophysical Journal
Volume 746, Página 47_1
fevereiro 2012

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