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 γ 1 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 m s −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 γ 1 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 .

Several dynamical processes may induce considerable electric currents in the atmospheres of magnetic chemically peculiar (CP) stars. The Lorentz force, which results from the interaction between the magnetic field and the induced currents, modifies the atmospheric structure and induces the characteristic rotational variability in the hydrogen Balmer lines. To study this phenomena we have initiated a systematic spectroscopic survey of the Balmer lines variation in magnetic CP stars. In this paper we continue presenting the results of the program, focusing on the high-resolution spectral observations of the A0p star θ Aur (HD 40312). We detected a significant variability in the Hα, Hβ, and Hγ spectral lines during the full rotation cycle of the star. This variability is interpreted in the framework of the model atmosphere analysis, which accounts for the Lorentz force effects. Both the inward-and outward-directed Lorentz forces are considered under the assumption of the axisymmetric dipole or dipole+quadrupole magnetic field configurations. We demonstrate that only the model with the outwardly directed Lorentz force in the dipole+quadrupole configuration is able to reproduce the observed hydrogen-line variation. These results present new strong evidence of non-zero global electric currents in the atmosphere of an earlytype magnetic star.

We present the first results from a high-precision radial velocity study of the K2 III giant star α Ari. Observations were acquired over 6 nights in 2004 using the new high-resolution spectrograph BOES (Bohyunsan Observatory Echelle Spectrograph) of the 1.8-m telescope. A high radial-velocity precision was achieved by using the high-resolution (R = 90 000) mode of BOES and an iodine gas absorption cell. The radial velocity measurements made during JD = 2 452 948−2 452 950 show coherent, low-amplitude variations with a period of P 1 = 0.571 days (or aliases at 0.445 or 0.821 days), and an amplitude of 18.9 m s −1 . Observations of τ Cet over this same interval are constant to within 3 m s −1 . After subtracting the contribution of the 0.57-day period, we find evidence for a second period, P 2 = 0.190 days. Observations made on a second run during JD = 2 452 975−2 452 981 show that the radial velocity variations are indeed present, but on shorter time-scales and with a lower amplitude. Two probable periods fit the radial velocity measurements from the second run reasonably well: 0.185 days or an alias of 0.256 days. The shorter period coincides with the secondary one found in the earlier measurements. We conclude that, similar to other K-giant pulsating stars, α Ari shows unstable acoustic pulsations or mode switching on time scales of tens of days. The calculated pulsation constants for the dominant 0.571-day period is consistent with third-overtone pulsations, while the secondary periodicity found in both data runs corresponds to a high overtone (n ≥ 12).