Discovery of a planet around the K giant star 4 Ursae Majoris
Abstract
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, f(m) = (2.05 ± 0.24) × 10- 7~M⊙. From our high resolution spectra we calculate a metallicity of -0.25 ± 0.05 and derive a stellar mass of 1.23 M⊙ ± 0.15 for the host star. The K giant star 4 UMa hosts a substellar companion with minimum mass M sin i = 7.1 ± 1.6 ~M_Jupiter.
Based on observations obtained at the 2-m-Alfred Jensch Telescope at the Thüringer Landessternwarte Tautenburg.- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 2007
- DOI:
- 10.1051/0004-6361:20066987
- arXiv:
- arXiv:astro-ph/0703672
- Bibcode:
- 2007A&A...472..649D
- Keywords:
-
- star: general;
- stars: variables;
- stars: individual: <ASTROBJ>4 UMa</ASTROBJ>;
- techniques: radial velocities;
- stars: late-type;
- stars: planetary systems;
- Astrophysics
- E-Print:
- 6 pages, 5 figures, 2 tables, accepted in A&