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PLANETARY COMPANION IN K GIANT σ PERSEI
이병철,한인우,박명구,David E. Mkrtichian,정광희,김강민,Gennady Valyavin 한국천문학회 2014 Journal of The Korean Astronomical Society Vol.47 No.2
We report the detection of an exoplanet candidate in orbit around σ Persei from a radial velocity (RV) survey. The system exhibits periodic RV variations of 579.8 ± 2.4 days. The purpose of the survey is to search for low-amplitude and long-period RV variations in giants and examine the origin of the variations using the fiber-fed Bohyunsan Observatory Echelle Spectrograph installed at the 1.8-m telescope of Bohyunsan Optical Astronomy Observatory in Korea. We present high-accuracy RV measurements of σ~Per made from December 2003 to January 2014. We argue that the RV variations are not related to the surface inhomogeneities but instead a Keplerian motion of the planetary companion is the most likely explanation. Assuming a stellar mass of 2.25 ± 0.5 M⊙, we obtain a minimum planetary companion mass of 6.5 ± 1.0 MJup, with an orbital semi-major axis of 1.8 ± 0.1 AU, and an eccentricity of 0.3 ± 0.1 around σ Per.
Lee, Byeong-Cheol,Jeong, Gwanghui,Park, Myeong-Gu,Han, Inwoo,Mkrtichian, David E.,Hatzes, Artie P.,Gu, Shenghong,Bai, Jinming,Lee, Sang-Min,Oh, Hyeong-Il,Kim, Kang-Min American Astronomical Society 2017 The Astrophysical journal Vol.844 No.1
<P>We present the detection of long-period RV variations in HD. 36384, HD. 52030, and HD. 208742 by using the high-resolution, fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) for the precise radial velocity (RV) survey of about 200 northern circumpolar stars. Analyses of RV data, chromospheric activity indicators, and bisector variations spanning about five years suggest that the RV variations are compatible with planet or brown dwarf companions in Keplerian motion. However, HD. 36384 shows photometric variations with a period very close to that of RV variations as well as amplitude variations in the weighted wavelet Z-transform (WWZ) analysis, which argues that the RV variations in HD. 36384 are from the stellar pulsations. Assuming that the companion hypothesis is correct, HD. 52030 hosts a companion with minimum mass 13.3 M-Jup orbiting in 484 days at a distance of 1.2 au. HD. 208742 hosts a companion of 14.0 M-Jup at 1.5 au with a period of 602 days. All stars are located at the asymptotic giant branch (AGB) stage on the H-R diagram after undergoing. the helium flash and leaving. the giant clump. With stellar radii of 53.0 R-circle dot and 57.2 R-circle dot for HD. 52030 and HD. 208742, respectively, these stars may be the largest yet, in terms of stellar radius, found to host substellar companions. However, given possible RV amplitude variations and the fact that these are highly evolved stars, the planet hypothesis is not yet certain.</P>
LONG-PERIOD VARIATIONS IN THE RADIAL VELOCITY OF SPECTROSCOPIC BINARY M GIANT<i>μ</i>URSAE MAJORIS
Lee, Byeong-Cheol,Han, Inwoo,Park, Myeong-Gu,Mkrtichian, David E.,Hatzes, Artie P.,Jeong, Gwanghui,Kim, Kang-Min American Astronomical Society 2016 The Astronomical journal Vol.151 No.4
<P>We report that the spectroscopic binary mu Ursae Majoris (mu UMa) has secondary RV variations of 471.2 days in addition to those of 230.0 days already known. Keplerian orbit analysis yields stellar mass companions of 1.6. M-circle dot for the 230 day period and 0.14. M-circle dot for the 471 day period. However, the HIPPARCOS photometries show a period similar to the stellar rotational period, which is one-quarter of the RV period. Variations in the bisector velocity curvature show a period of 463.6 days. We also find similar to 473 day variations in the equivalent width (EW) measurements of the H-alpha and H-beta lines, whose origin is probably stellar activity. We note that the nature of 471 day variations is similar to one observed in 'Sequence D' of Asymptotic Giant Branch pulsating stars. We therefore conclude that the RV and the EW variations in the spectroscopic binary M giant mu UMa. A originate from the complex pulsations and the chromospheric activity.</P>