Detection of planet candidates around K giants, HD 40956, HD 111591, and HD 113996

Aims. The purpose of this paper is to detect and investigate the nature of long-term radial velocity (RV) variations of K-type giants and to confirm planetary companions around the stars. Methods. We have conducted two planet search programs by precise RV measurement using the 1.8 m telescope at Bohyunsan Optical Astronomy Observatory (BOAO) and the 1.88 m telescope at Okayama Astrophysical Observatory (OAO). The BOAO program searches for planets around 55 early K giants. The OAO program is looking for 190 G-K type giants. Results. In this paper, we report the detection of long-period RV variations of three K giant stars, HD 40956, HD 111591, and HD 113996. We investigated the cause of the observed RV variations and conclude the substellar companions are most likely the cause of the RV variations. The orbital analyses yield P = 578.6 $\pm$ 3.3 d, $m$ sin $i$ = 2.7 $\pm$ 0.6 $M_{\rm{J}}$, $a$ = 1.4 $\pm$ 0.1 AU for HD 40956; P = 1056.4 $\pm$ 14.3 d, $m$ sin $i$ = 4.4 $\pm$ 0.4 $M_{\rm{J}}$, $a$ = 2.5 $\pm$ 0.1 AU for HD 111591; P = 610.2 $\pm$ 3.8 d, $m$ sin $i$ = 6.3 $\pm$ 1.0 $M_{\rm{J}}$, $a$ = 1.6 $\pm$ 0.1 AU for HD 113996.Comment: 10 pages, 12 figures. Accepted for publication in Astronomy & Astrophysic

A search for exoplanets around north circumpolar stars. VII. Detection of planetary companion orbiting the largest host star HD 18438

We have been conducting a exoplanet search survey using Bohyunsan Observatory Echelle Spectrograph (BOES) for the last 18 years. We present the detection of exoplanet candidate in orbit around HD 18438 from high-precision radial velocity (RV) mesurements. The target was already reported in 2018 (Bang et al. 2018). They conclude that the RV variations with a period of 719 days are likely to be caused by the pulsations because the Lomb-Scargle periodogram of HIPPARCOS photometric and Ha EW variations for HD 18438 show peaks with periods close to that of RV variations and there were no correlations between bisectors and RV measurements. However, the data were not sufficient to reach a firm conclusion. We obtained more RV data for four years. The longer time baseline yields a more accurate determination with a revised period of 803 +/- 5 days and the planetary origin of RV variations with a minimum planetary companion mass of 21 +/- 1 MJup. Our current estimate of the stellar parameters for HD 18438 makes it currently the largest star with a planetary companion.Comment: 6 pages, 4 figures, Accept to the Journal of the Korean Astronomical Societ

Hybrid star HD 81817 accompanied by brown dwarf or substellar companion

HD 81817 is known as a hybrid star. Hybrid stars have both cool stellar wind properties and Ultraviolet (UV) or even X-ray emission features of highly ionized atoms in their spectra. A white dwarf companion has been suggested as the source of UV or X-ray features. HD 81817 has been observed since 2004 as a part of a radial velocity (RV) survey program to search for exoplanets around K giant stars using the Bohyunsan Observatory Echelle Spectrograph at the 1.8 m telescope of Bohyunsan Optical Astronomy Observatory in Korea. We obtained 85 RV measurements between 2004 and 2019 for HD 81817 and found two periodic RV variations. The amplitudes of RV variations are around 200 m s^-1, which are significantly lower than that expected from a closely orbiting white dwarf companion. Photometric data and relevant spectral lines were also analyzed to help determine the origin of the periodic RV variations. We conclude that 627.4-day RV variations are caused by intrinsic stellar activities such as long-term pulsations or rotational modulations of surface activities based on H{\alpha} equivalent width (EW) variations of a similar period. On the other hand, 1047.1-day periodic RV variations are likely to be caused by a brown dwarf or substellar companion, which is corroborated by a recent GAIA proper motion anomaly for HD 81817. The Keplerian fit yields a minimum mass of 27.1 M_Jup, a semimajor axis of 3.3 AU, and an eccentricity of 0.17 for the stellar mass of 4.3 M_sun for HD 81817. The inferred mass puts HD 81817 b in the brown dwarf desert

Exploring the Role of a Novel Peptide from Allomyrina dichotoma Larvae in Ameliorating Lipid Metabolism in Obesity

The aim of this study was to identify an anti-obesity peptide from Allomyrina dichotoma and investigate the lipid metabolic mechanism. Enzymatically hydrolyzed A. dichotoma larvae were further separated using tangential flow filtration and consecutive chromatographic processes. Finally, an anti-obesity peptide that showed the highest inhibitory effect on lipid accumulation was obtained, and the sequence was Glu-Ile-Ala-Gln-Asp-Phe-Lys-Thr-Asp-Leu (EIA10). EIA10 decreased lipid aggregation in vitro and significantly reduced the accumulation of body weight gain, liver weight, and adipose tissue weight in high-fat-fed mice. Compared with the control group, the levels of total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL), insulin, and homeostasis model assessment of insulin resistance (HOMA-IR) in the high-fat diet (HFD) group increased significantly, and the content of high-density lipoprotein cholesterol (HDL) in the serum decreased significantly. On the contrary, the levels of TC, TG, and insulin in the EIA10 group decreased significantly, and the HDL content increased significantly compared with the HFD group. Additionally, EIA10 dramatically decreased mRNA and protein levels of transcription factors involved in lipid adipogenesis. Taken together, our results suggest that EIA10 could be a promising agent for the treatment and prevention of obesity