Volume 472, Number 2, September III 2007
|Page(s)||649 - 652|
|Section||Planets and planetary systems|
|Published online||26 March 2007|
Discovery of a planet around the K giant star 4 Ursae Majoris*
European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany e-mail: firstname.lastname@example.org
2 Max-Planck-Institut für Astrophysik, Garching bei München, Germany
3 Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
4 INAF-Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy
5 Dipartimento di Fisica “E.R. Caianiello”, Universita di Salerno, via S. Allende, 84081 Baronissi (Salerno), Italy
Accepted: 2 March 2007
For the past 3 years we have been monitoring a sample of 62 K giant stars using precise stellar radial velocity measurements with high accuracy taken at the Thüringer Landessternwarte Tautenburg. We search for sub-stellar companions to giant stars and try to understand the nature of the diverse radial velocity variations exhibited by K giant stars. We present precise stellar radial velocity measurements of the K1III giant star 4 UMa (HD 73108). These were obtained using the coudé echelle spectrograph of 2-m Alfred Jensch Telescope. The wavelength reference for the radial velocity measurements was provided by an iodine absorption cell. Our measurements reveal that the radial velocity of 4 UMa exhibits a periodic variation of 269.3 days with a semiamplitude K = 216.8 m s-1. A Keplerian orbit with an eccentricity, e = 0.43 ± 0.02 is the most reasonable explanation for the radial velocity variations. The orbit yields a mass function, . From our high resolution spectra we calculate a metallicity of -0.25 ± 0.05 and derive a stellar mass of 1.23 for the host star. The K giant star 4 UMa hosts a substellar companion with minimum mass .
Key words: star: general / stars: variables / stars: individual: 4 UMa / techniques: radial velocities / stars: late-type / stars: planetary systems
© ESO, 2007
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