Mon. Not. R. Astron. Soc., 450, 1900-1915 (2015/June-3)
Chemical abundances and kinematics of 257 G-, K-type field giants. Setting a base for further analysis of giant-planet properties orbiting evolved stars.
ADIBEKYAN V.Z., BENAMATI L., SANTOS N.C., ALVES S., LOVIS C., UDRY S., ISRAELIAN G., SOUSA S.G., TSANTAKI M., MORTIER A., SOZZETTI A. and DE MEDEIROS J.R.
Abstract (from CDS):
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-logg stars with high metallicities, and high-logg 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 logg-[Fe/H] diagram to overcome the aforementioned issue.
© 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society (2015)
methods: observational - techniques: spectroscopic - stars: abundances - planetary systems
VizieR on-line data:
<Available at CDS (J/MNRAS/450/1900): table2.dat ab_best.dat vel.dat ew.dat linelist.dat>
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