Protostars and Planets VI, Heidelberg, July 15-20, 2013

Poster 2K028

Giant Planet Occurrence Rate as a Function of Stellar Mass

Reffert, Sabine (Landessternwarte Heidelberg, Germany)
Bergmann, Christoph (Landessternwarte Heidelberg, Germany & University of Canterbury, Christchurch, New Zealand)
Quirrenbach, Andreas (Landessternwarte Heidelberg, Germany)
Trifonov, Trifon (Landessternwarte Heidelberg, Germany)
Künstler, Andreas (Landessternwarte Heidelberg, Germany & Leibniz-Institut für Astrophysik, Potsdam, Germany)

For over 12 years we have carried out a Doppler survey at Lick Observatory, identifying 15 planets and 20 candidate planets in a sample of 373 G and K giant stars. We investigate giant planet occurrence rate as a function of stellar mass and metallicity in this sample, which covers the mass range from about 1 to 3.5-5.0 solar masses. We confirm the presence of a strong planet-metallicity correlation in our giant star sample, which is fully consistent with the well-known planet-metallicity correlation for main-sequence stars. Furthermore, we find a very strong dependence of the giant planet occurrence rate on stellar mass, which we fit with a gaussian distribution. Stars with masses of about 1.9 solar masses have the highest probability of hosting a giant planet, whereas the planet occurrence rate drops rapidly for masses larger than 2.5 to 3.0 solar masses. We do not find any planets around stars more massive than 2.7 solar masses, although we have 113 stars with masses between 2.7 and 5.0 solar masses in our sample (planet occurrence rate in that mass range: 0% +1.6% at 68.3% confidence). This result is not due to a bias related to planet detectability as a function of stellar mass. We conclude that larger mass stars do not form giant planets which are observable at orbital distances of a few AU today. Possible reasons include slower growth rate due to the snow-line being located further out, longer migration timescale and faster disk depletion.

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