Detection of a Planetary Companion around the giant star \gam1leo

Abstract

Aims: Our primary goal is to search for planets around intermediate mass stars. We are also interested in studying the nature of radial velocity (RV) variations of K giant stars. Methods: We selected about 55 early K giant (K0 - K4) stars brighter than fifth magnitude that were observed using BOES, a high resolution spectrograph attached to the 1.8 m telescope at BOAO (Bohyunsan Optical Astronomy Observatory). BOES is equipped with $I_2$ absorption cell for high precision RV measurements. Results: We detected a periodic radial velocity variations in the K0 III star \gam1leo with a period of P = 429 days. An orbital fit of the observed RVs yields a period of P = 429 days, a semi-amplitude of K = 208 \mps, and an eccentricity of e = 0.14. To investigate the nature of the RV variations, we analyzed the photometric, CaII $\lambda$ 8662 equivalent width, and line-bisector variations of \gam1leo. We conclude that the detected RV variations can be best explained by a planetary companion with an estimated mass of m $\sin i = 8.78 M_{Jupiter}$ and a semi-major axis of $a = 1.19$ AU, assuming a stellar mass of 1.23 \Msun.