Precise radial velocities of giant stars: VII. Occurrence rate of giant extrasolar planets as a function of mass and metallicity

We have obtained precise radial velocities for a sample of 373 G and K type giants at Lick Observatory regularly over more than 12 years. Planets have been identified around 15 of these giant stars, and an additional 20 giant stars host planet candidates. We are interested in the occurrence rate of...

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Bibliographic Details
Published in:Astronomy and astrophysics (Berlin) 2015-02, Vol.574, p.A116
Main Authors: Reffert, Sabine, Bergmann, Christoph, Quirrenbach, Andreas, Trifonov, Triton, Kunstler, Andreas
Format: Article
Language:English
Subjects:
Extrasolar planets
Giant stars
Metallicity
Migration
Planet formation
Planetary probes
Radial velocity
Stellar mass
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Summary:We have obtained precise radial velocities for a sample of 373 G and K type giants at Lick Observatory regularly over more than 12 years. Planets have been identified around 15 of these giant stars, and an additional 20 giant stars host planet candidates. We are interested in the occurrence rate of sub-stellar companions around giant stars as a function of stellar mass and metallicity. We probe the stellar mass range from approximately 1 to beyond 3 M , which is not being explored by main-sequence samples. We fit the giant planet occurrence rate as a function of stellar mass and metallicity with a Gaussian and an exponential distribution, respectively. We find strong evidence for a planet-metallicity correlation among the secure planet hosts of our giant star sample, in agreement with the one for main-sequence stars. We conclude that giant planet formation or inward migration is suppressed around higher mass stars, possibly because of faster disk depletion coupled with a longer migration timescale.
ISSN:0004-6361
1432-0746
DOI:10.1051/0004-6361/201322360