Context :

Aims : We have been carrying out a precise radial velocity ( RV ) survey for K giants to search for and study the origin of the low-amplitude and long-periodic RV variations .

Methods : We present high-resolution RV measurements of the K2 giant HD 66141 from December 2003 to January 2011 using the fiber-fed Bohyunsan Observatory Echelle Spectrograph ( BOES ) at Bohyunsan Optical Astronomy Observatory ( BOAO ) .

Results : We find that the RV measurements for HD 66141 exhibit a periodic variation of 480.5 \pm 0.5 days with a semi-amplitude of 146.2 \pm 2.7 m s ^ { -1 } .
The Hipparcos photometry and bisector velocity span ( BVS ) do not show any obvious correlations with RV variations .
We find indeed 706.4 \pm 35.0 day variations in equivalent width ( EW ) measurements of H _ { \alpha } line and 703.0 \pm 39.4 day variations in a space-born measurements 1.25 \mu flux of HD 66141 measured during COBE/DIRBE experiment .
We reveal that a mean value of long-period variations is about 705 \pm 53 days and the origin is a rotation period of the star and variability that is caused by surface inhomogeneities .
For the 480 day periods of RV variations an orbital motion is the most likely explanation .
Assuming a stellar mass of 1.1 \pm 0.1 \it M _ { \odot } for HD 66141 , we obtain a minimum mass for the planetary companion of 6.0 \pm 0.3 M _ { \mathrm { Jup } } with an orbital semi-major axis of 1.2 \pm 0.1 AU and an eccentricity of 0.07 \pm 0.03 .

Conclusions :