Detection of a planetary companion around the giant star γ1 Leonis

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 γ¹ Leonis 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 ms^-1, and an eccentricity of e = 0.14. To investigate the nature of the RV variations, we analyzed the photometric, Ca II λ 8662 equivalent width, and line-bisector variations of γ¹ Leonis. 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 M_⊙.

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