* Astronomy

Title: A planetary companion around the K giant eps Corona Borealis
Authors: Byeong-Cheol Lee, Inwoo Han, Myeong-Gu Park, David E. Mkrtichian, Kang-Min Kim

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 fibre-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 solar masses for epsilon CrB, we obtain a minimum mass for the planetary companion of 6.7 ± 0.3 Jupiter masses 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.

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