Radial Velocity Variation in Red Giants

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A survey of radial velocity variations in nearby red giants has been conducted since 1999 using ESO and TLS spectrographs. The main target is the characterization of the radial velocity variations due to surface unhomogeneity, pulsation, and/or low mass companions.

 

 It has been shown that all of the three factors contribute to the observed radial velocity variations. Planets were found orbiting the stars 4 UMa, HD 11977, and HD 47536. The analysis of chemical abundances for the initial sample reveals an age-metallicity relation which is surprisingly flat and with little dispersion at the youngest ages. Also, giants hosting planets are found not to be as metal rich as the dwarfs, which hint to an external origin (pollution by planetary debris) of enhanced metallicity in planet-hosting stars. The project continues with HARPS at the 3.6m ESO telescope and with the Thueringer Landessternwarte Tautenburg 2m telescope.

People: Leo Girardi

Collaboration: Luca Pasquini (ESO), Artie Hatzes (Tautenburg Landsternwarte), Johnyy Setiawan, Michaela Doellinger (MPIA Heidelberg), J. Renan de Medeiros (UFRN, Natal)

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