Galactic stellar populations and planets for the HARPS GTO sample

E. Delgado Mena, V. Zh. Adibekyan, N. C. Santos, S. G. Sousa, G. Israelian, J. I. González Hernández, M. Mayor, G. Khachatryan

Abstract.
We present the results of a uniform, precise, and detailed abundance analysis of 12 refractory elements in a large sample of 1111 FGK dwarf stars from the HARPS GTO planet search program. The sample contains 109 giant planet-hosts and 26 stars with exclusively Neptunians and super-Earths.
The large number of stars and the high precision of our unique measurements allow us to confirm the existence of a new (previously unidentified) galactic population of high-alfa content metal rich stars. These stars have kinematic properties similar to those of thin disc objects, but ages more similar to thick disk stars. We also show that the chemically separated thin and thick discs are also chemically disjunct for Al, Sc, Co and Ca.
We confirm that an overabundance in giant-planet host stars is clear for all the studied elements. Finally, we also confirm that stars hosting only Neptunian-like planets may be easier to detect around stars with similar metallicities as non-planet hosts, although for some elements (particulary alfa-elements) the lower limit of [X/H] are very abrupt. We then explore new correlations between chemical abundances and the presence of planets, including the frequency of planets in the different galactic populations.

GREAT ESF-sponsored Workshop
The metallicity distribution in the Milky Way discs
Bologna, Italy
May 2012

Type: Oral comunication