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)
Abstract:
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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