• Journal of The Korean Astronomical Society
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• v.51 no.1
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• pp.17-25
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• 2018

Detecting exoplanets around giant stars sheds light on the later-stage evolution of planetary systems. We observed the M giant HD 18438 and the K giant HD 158996 as part of a Search for Exoplanets around Northern circumpolar Stars (SENS) and obtained 38 and 24 spectra from 2010 to 2017 using the high-resolution Bohyunsan Observatory Echelle Spectrograph (BOES) at the 1.8m telescope of Bohyunsan Optical Astronomy Observatory in Korea. We obtained precise RV measurements from the spectra and found long-period radial velocity (RV) variations with period 719.0 days for HD 18438 and 820.2 days for HD 158996. We checked the chromospheric activities using Ca $\text\tiny{II}$ H and $H{\alpha}$ lines, HIPPARCOS photometry and line bisectors to identify the origin of the observed RV variations. In the case of HD 18438, we conclude that the observed RV variations with period 719.0 days are likely to be caused by the pulsations because the periods of HIPPARCOS photometric and $H{\alpha}$ EW variations for HD 18438 are similar to that of RV variations in Lomb-Scargle periodogram, and there are no correlations between bisectors and RV measurements. In the case of HD 158996, on the other hand, we did not find any similarity in the respective periodograms nor any correlation between RV variations and line bisector variations. In addition, the probability that the real rotational period can be as longer than the RV period for HD 158996 is only about 4.3%. Thus we conclude that observed RV variations with a period of 820.2 days of HD 158996 are caused by a planetary companion, which has the minimum mass of 14.0 $M_{Jup}$, the semi-major axis of 2.1 AU, and eccentricity of 0.13 assuming the stellar mass of $1.8 M_{\odot}$. HD 158996 is so far one of the brightest and largest stars to harbor an exoplanet candidate.

• Journal of Astronomy and Space Sciences
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• v.26 no.2
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• pp.141-156
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• 2009

Through the photometric observations of the near-contact binary, XZ CMi, new BV light curves were secured and seven times of minimum light were determined. An intensive period study with all published timings, including ours, confirms that the period of XZ CMi has varied in a cyclic period variation superposed on a secular period decrease over last 70 years. Assuming the cyclic change of period to occur by a light-time effect due to a third-body, the light-time orbit with a semi-amplitude of 0.0056d, a period of 29y and an eccentricity of 0.71 was calculated. The observed secular period decrease of $-5.26{\times}10^{-11}d/P$ was interpreted as a result of simultaneous occurrence of both a period decrease of $-8.20{\times}10^{-11}d/P$ by angular momentum loss (AML) due to a magnetic braking stellar wind and a period increase of $2.94{\times}10^{-11}d/P$ by a mass transfer from the less massive secondary to the primary components in the system. In this line the decreasing rate of period due to AML is about 3 times larger than the increasing one by a mass transfer in their absolute values. The latter implies a mass transfer of $\dot{M}_s=3.21{\times}10^{-8}M_{\odot}y^{-1}$ from the less massive secondary to the primary. The BV light curves with the latest Wilson-Devinney binary code were analyzed for two separate models of 8200K and 7000K as the photospheric temperature of the primary component. Both models confirm that XZ CMi is truly a near-contact binary with a less massive secondary completely filling Roche lobe and a primary inside the inner Roche lobe and there is a third-light corresponding to about 15-17% of the total system light. However, the third-light source can not be the same as the third-body suggested from the period study. At the present, however, we can not determine which one between two models is better fitted to the observations because of a negligible difference of $\sum(O-C)^2$ between them. The diversity of mass ratios, with which previous investigators were in disagreement, still remains to be one of unsolved problems in XZ CMi system. Spectroscopic observations for a radial velocity curve and high-resolution spectra as well as a high-precision photometry are needed to resolve some of remaining problems.

• (The)Study of the Eastern Classic
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• no.66
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• pp.331-362
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• 2017

The paintings of the Eight Drunken Immortals refer to the paintings based on an influential poem called "The Song of the Eight Drunken Immortals" by Du Fu, a Chinese poet from the Tang Dynasty. This poem is about the eccentricity of the Eight Immortals known for their love of drinking. The Eight Drunken Immortals have been widely appreciated among East Asian intellectuals, and their stories have also been translated into paintings. Greatly influenced by Li Gonglin's Painting of the Eight Drunken Immortals, people in China have the tendency to create similar scroll paintings, using contour drawing tools. Meanwhile, in Korea, the paintings of the Eight Drunken Immortals have been widely appreciated both as a type of visual art embodying the Drunken Immortals' taste for the arts and as a meaningful object conveying the people's wish for longevity and eternal friendship. According to historical records, the paintings of the Eight Drunken Immortals from the Ming Dynasty were drawn on eight-fold folding screens using a sophisticated ink wash painting technique. In the meantime, the Painting of the Eight Drunken Immortals appreciated by King Jeongjo from the Joseon Dynasty was a colored landscape painting with small human figures on an eight-fold folding screen. Since the recent discovery of Yi Han-cheol's Painting of the Eight Drunken Immortals on an eight-fold folding screen, it has now become possible to imagine how renowned artists such as Kim Hong-do and Kim Yang-gi would have made the narrative figure paintings. In particular, the story of Li Bai, one of the Eight Immortals, was the most famous one often told in the paintings. After the 19th century, there was even an entire panel of narrative folding screen made about Li Bai. As painting manuals and outline drawings were pervasively used, the narrative paintings on Li Bai were mass-produced among commoners. As you can see from this, the Eight Drunken Immortals have been visually represented as thirsty souls who are not disconnected from the world, as honest men of refined taste for the arts, and as protagonists of an object that conveys the people's wish for longevity and eternal friendship. In other words, the paintings of the Eight Drunken Immortals embody multiple undertones: as paintings based on Du Fu's poems and as narrative paintings on the Eight Immortals.