Aims. Our aim is to search for and study the origin of the low-amplitude and
long-periodic radial velocity (RV) variations in K giants. Methods. We present
high-resolution RV measurements of K2 giant epsilon CrB from February 2005 to
January 2012 using the fiber-fed Bohyunsan Observatory Echelle Spectrograph
(BOES) at the Bohyunsan Optical Astronomy Observatory (BOAO). Results. We find
that the RV measurements for epsilon CrB exhibit a periodic variation of 417.9
+/- 0.5 days with a semi-amplitude of 129.4 +/- 2.0 m/s. There is no
correlation between RV measurements and chromospheric activity in the Ca II H
region, the Hipparcos photometry, or bisector velocity span. Conclusions.
Keplerian motion is the most likely explanation, with the RV variations arising
from an orbital motion. Assuming a possible stellar mass of 1.7 +/- 0.1 M_Sun
for epsilon CrB, we obtain a minimum mass for the planetary companion of 6.7
+/- 0.3 M_Jup with an orbital semi-major axis of 1.3 AU and eccentricity of
0.11. We also discuss the implications of our observations for stellar
metallicity versus planet occurrence rate and stellar mass versus planetary
mass relations.Comment: 5 pages, 7 figures, 3 tables, accepted for publisation in Astronomy &
Astrophysic
