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Medientyp:
E-Artikel
Titel:
Precise radial velocities of giant stars : XIV. Evidence of planetary companions around HD 25723, 17 Sco, 3 Cnc, and 44 UMa
:
XIV. Evidence of planetary companions around HD 25723, 17 Sco, 3 Cnc, and 44 UMa
Beteiligte:
Pinto, Marcelo Tala;
Reffert, Sabine;
Quirrenbach, Andreas;
Stock, Stephan;
Trifonov, Trifon;
Mitchell, David S.
Beschreibung:
<jats:p><jats:italic>Context.</jats:italic> More than 100 exoplanets have been discovered around K and G giant stars, and their properties differ considerably from those of the planets found orbiting Sun-like and late-type main-sequence stars. This allows us to study the properties of planetary systems after the host star has evolved off the main-sequence, and it helps us to constrain planetary formation and evolution models.</jats:p>
<jats:p><jats:italic>Aims.</jats:italic> Our aim is to find out whether the long-period radial velocity variations observed in four giant stars of the Lick survey are caused by orbiting planets, and to study the properties of the planet population as a function of the stellar evolutionary stage.</jats:p>
<jats:p><jats:italic>Methods.</jats:italic> We analyzed 12 yr of precise radial velocity data for four stars of the Lick sample. In addition, we compared the planet frequency as a function of the evolutionary stage for two surveys, Lick and Express, based on the evolutionary stages derived using Bayesian inference.</jats:p>
<jats:p><jats:italic>Results.</jats:italic> We report the discovery of two new exoplanets and three exoplanet candidates orbiting giant stars. The best Keplerian fits to the data yield minimum masses of 2.5 <jats:italic>M</jats:italic><jats:sub>J</jats:sub> and 4.3 <jats:italic>M</jats:italic><jats:sub>J</jats:sub> for the planets orbiting HD 25723 and 17 Sco, respectively. The minimum masses of an additional candidate around HD 25723, and of planet candidates around 3 Cnc and 44 UMa, would be 1.3 <jats:italic>M</jats:italic><jats:sub>J</jats:sub>, 20.7 <jats:italic>M</jats:italic><jats:sub>J,</jats:sub> and 12.1 <jats:italic>M</jats:italic><jats:sub>J</jats:sub>, respectively. In addition, we compute planet frequencies for the Lick and Express samples as a function of the evolutionary stage. Within each sample, the planet frequency for the horizontal branch stars is the same as for the red giant branch stars.</jats:p>
<jats:p><jats:italic>Conclusions.</jats:italic> We have discovered two new exoplanets and three new exoplanet candidates, one of them being the second planet in a possible multi-planetary system. Based on our derived planet frequencies, we conclude that stellar evolution does not affect the number of observable planets between the red-giant and horizontal-branch evolutionary stages.</jats:p>