• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.60.2-60.2
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• 2019

Based on our experience on exoplanet transit observation, we propose the exoplanet science cases with Small Telescope Network. One is the follow-up observation for validation of exoplanet candidates. TESS(Transiting Exoplanet Survey Satellite) is pouring out exoplanet candidates in bright stars(V<15) on all the sky. Since Small Telescope Network will consist of 0.5-1m telescopes, we will expect to produce promising outcomes from the follow-up observation of bright candidates. Next is the transit time observation. By spectroscopy of space and large telescopes during transit event, it can be possible to find the bio signatures in exoplanet atmosphere. So, in terms of cost, it is critical to determine the exact time of transit event. In addition, detecting the variation of transit time can reveal another exoplanet and exomoon in the system. In order to determine the transit time and its variation, the accumulation of transit event data is more important than the quality of photometric data. We expect that it can be a challenging project of Small Telescope Network.

• Journal of Astronomy and Space Sciences
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• v.33 no.4
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• pp.257-264
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• 2016

A planet revolving around binary star system is a familiar system. Studies of these systems are important because they provide precise knowledge of planet formation and orbit evolution. In this study, a method to determine the evolution of an exoplanet revolving around a binary star system using different rates of stellar mass loss will be introduced. Using a hierarchical triple body system, in which the outer body can be moved with the center of mass of the inner binary star as a two-body problem, the long period evolution of the exoplanet orbit is determined depending on a Hamiltonian formulation. The model is simulated by numerical integrations of the Hamiltonian equations for the system over a long time. As a conclusion, the behavior of the planet orbital elements is quite affected by the rate of the mass loss from the accompanying binary star.

• Publications of The Korean Astronomical Society
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• v.38 no.2
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• pp.13-24
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• 2023

More than 5,000 exoplanets have been detected nowadays. One of the key motivations of exoplanet detection is to understand what physical/chemical conditions of exoplanets are suitable for harboring extraterrestrial life. Such conditions are called "habitability," and most modern studies assume the existence of liquid water as its key factor. In this paper, we review the current status of exoplanet and habitability studies, as well as some future (habitable) exoplanet survey plans, mostly from National Academies of Sciences, Engineering, and Medicine (2018, 2021). Also, we suggest several research items that the Korean astronomy and space science community could contribute to habitability.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.76.2-76.2
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• 2012

The understanding spectral characterization of possible earth-like extra solar planets has generated wide interested in astronomy and space science. The technical central issue in observation of exoplanet is deconvolution of the temporally and disk-averaged spectra of the exoplanets. The earth model based on atmospheric radiative transfer method has been studied in recent years for solutions of characterization of earthlike exoplanet. In this study, we report on the current progress of the new method of 3D earth model as a habitable exoplanet. The computational model has 3 components 1) the sun model, 2) an integrated earth BRDF (Bi-directional Reflectance Distribution Function) model (Atmosphere, Land and Ocean) and 3) instrument model combined in ray tracing computation. The ray characteristics such as radiative power and direction are altered as they experience reflection, refraction, transmission, absorption and scattering from encountering with each all of optical surfaces. The Land BRDF characteristics are defined by the semi-empirical "parametric-kernel-method" from POLDER missions from CNES. The ocean BRDF is defined for sea-ice cap structure and for the sea water optical model, considering sun-glint scattering. The input cloud-free atmosphere model consists of 1 layers with vertical profiles of absorption and aerosol scattering combined Rayleigh scattering and its input characteristics using the NEWS product in NASA data and spectral SMARTS from NREL and 6SV from Vermote E. The trial simulation runs result in phase dependent disk-averaged spectra and light-curves of a virtual exoplanet using 3D earth model.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.51.3-51.3
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• 2017

We present a general N-body exoplanet simulator in anticipation of upcoming next generation telescopes. Illustrative examples are presented on P-type orbits in stellar binary stellar systems, that should be fairly common as in Kepler 16AB. Specific attention is paid to reduced orbital lfetimes of exoplanets in the habitable zone by the stellar binary, known from Dvorak (1986).

• Journal of The Korean Astronomical Society
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• v.41 no.3
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• pp.59-64
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• 2008

To detect exoplanets and study pulsation of K giant stars, we have observed precise RV (radial velocity) of about 55 early K giant (K0 - K4) stars brighter than V = 5 magnitude since 2003 by using BOES, a high resolution Echelle spectrograph attached to the 1.8 m telescope at BOAO (Bohyunsan Optical Astronomy Observatory). We detected periodic RV variation of KO III star $\beta$ Gem (HD 62509) with a period $P\;=\;596.6\;{\pm}\;2.3$ days and a semi-amplitude $K\;=\;44.8\;{\pm}\;0.7\;ms^{-1}$. If we adopt 1.7 $M_{\odot}$ for the mass of $\beta$ Gem, this yields the minimum mass of the companion m sin i = 2.64 $M_{Jupiter}$. Our results agree well with Hatzes et al. (2006) and Reffert et al. (2006), and confirm their discovery of a planetary object around $\beta$ Gem. We also confirmed about 192 minutes short period stellar oscillation found by Hatzes and Zechmeister (2007). This is the first report of exoplanet detection using BOES and demonstrates that the RV observation using BOES is accurate and stable enough to detect exoplanets around bright K giant stars.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.28.2-28.2
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• 2011

To search for and study the nature of the long-periodic variations of massive stars, we have been carrying out a precise radial velocity (RV) survey for supergiants. Here, we present high-resolution RV measurements of ${\alpha}$ Per which lies near the Cepheid instability strip from November 2005 to February 2011 using the fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) at Bohyunsan Optical Astronomy Observatory (BOAO). The orbital solution yields a period of 129 days, a 2K amplitude of 80 m/s, and an eccentricity of 0.1. Assuming a possible stellar mass of 7.3 $M{\bigodot}$, we estimate the minimum mass for the planetary companion to be 7.5 MJup with the orbital semi-major axis of 0.97 AU. We do not find the correlation between RV variations and chromospheric activity indicator (Ca II H & K region). The Hipparcos photometry and bisector velocity span (BVS) do not show any obvious correlations with RV variations. These analyses suggest that ${\alpha}$ Per is a pulsating supergiant that hosts an exoplanet. If the 129 days variations of ${\alpha}$ Per do not come from an exoplanet but Cepheid-like pulsations, the theoretical boundary of the Cepheid instability strip may need to be extended to the bluer side.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.90.1-90.1
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• 2015

Almost hot-Super Earths ($R_p$~1 to $4R_{earth}$ orbital period < 100 days) are around Sun-like stars. But our solar system does not have hot-Super Earth. Andre et al. 2015 has explained this phenomenon by that Jupiter blocks migration of super earth. We have found a multi-planetary system KOI-94 with exo-Jupiter and hot-Super Earth from NASA exoplanet archive data (http://exoplanetarchive.ipac.caltech.edu). In this study, within multi-planetary systems including hot-Super Earth, we compared those with and without exo-Jupiter using their host star and exoplanet parameters, such as metallicity [Fe/H], $T_{eff}$ and $R_*/R_p$.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.58.1-58.1
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• 2016

During the year 2016 the newly installed NYSC (National Youth Science Center) 1m optical telescope was officially commissioned. Calls for future observational programmes were announced. During test observations we carried out an observational project aimed at follow-up observations of transiting extrasolar planets. To predict future transits we developed the "TransitSearch" code implemented in Python utilizing transit information from the Open Exoplanet Catalogue. During three nights in April and June 2016 we observed planetary transits of HAT-P-3b and TrES-3b. Preliminary light curves of the transit events are presented alongside with best-fit models. From this experience we plan to improve the optical alignment and photometric performance by operating the 1m NYSC telescope in a strongly out-of-focus mode for transit observations.

• The Bulletin of The Korean Astronomical Society
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• v.34 no.1
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• pp.97.2-97.2
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• 2009