Bibcode
Döllinger, M. P.; Hatzes, A. P.; Pasquini, L.; Guenther, E. W.; Hartmann, M.; Girardi, L.; Esposito, M.
Bibliographical reference
Astronomy and Astrophysics, Volume 472, Issue 2, September III 2007, pp.649-652
Advertised on:
9
2007
Journal
Citations
69
Refereed citations
61
Description
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&sun;.
From our high resolution spectra we calculate a metallicity of -0.25
± 0.05 and derive a stellar mass of 1.23 M&sun;
± 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.