Bibcode
Adibekyan, V. Zh.; Benamati, L.; Santos, N. C.; Alves, S.; Lovis, C.; Udry, S.; Israelian, G.; Sousa, S. G.; Tsantaki, M.; Mortier, A.; Sozzetti, A.; De Medeiros, J. R.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 450, Issue 2, p.1900-1915
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6
2015
Citations
27
Refereed citations
24
Description
We performed a uniform and detailed abundance analysis of 12 refractory
elements (Na, Mg, Al, Si, Ca, Ti, Cr, Ni, Co, Sc, Mn, and V) for a
sample of 257 G- and K-type evolved stars from the CORALIE planet search
programme. To date, only one of these stars is known to harbour a
planetary companion. We aimed to characterize this large sample of
evolved stars in terms of chemical abundances and kinematics, thus
setting a solid base for further analysis of planetary properties around
giant stars. This sample, being homogeneously analysed, can be used as a
comparison sample for other planet-related studies, as well as for
different type of studies related to stellar and Galaxy astrophysics.
The abundances of the chemical elements were determined using an local
thermodynamic equilibrium (LTE) abundance analysis relative to the Sun,
with the spectral synthesis code MOOG and a grid of Kurucz ATLAS9
atmospheres. To separate the Galactic stellar populations, both a purely
kinematical approach and a chemical method were applied. We confirm the
overabundance of Na in giant stars compared to the field FGK dwarfs.
This enhancement might have a stellar evolutionary character, but
departures from LTE may also produce a similar enhancement. Our chemical
separation of stellar populations also suggests a `gap' in metallicity
between the thick-disc and high-α metal-rich stars, as previously
observed in dwarfs sample from HARPS. The present sample, as most of the
giant star samples, also suffers from the B - V colour cut-off, which
excludes low-log g stars with high metallicities, and high-log g star
with low [Fe/H]. For future studies of planet occurrence dependence on
stellar metallicity around these evolved stars, we suggest to use a
subsample of stars in a `cut-rectangle' in the log g-[Fe/H] diagram to
overcome the aforementioned issue.
Related projects
Observational Tests of the Processes of Nucleosynthesis in the Universe
Several spectroscopic analyses of stars with planets have recently been carried out. One of the most remarkable results is that planet-harbouring stars are on average more metal-rich than solar-type disc stars. Two main explanations have been suggested to link this metallicity excess with the presence of planets. The first of these, the “self
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Israelian