• 천문학회보
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• 제43권1호
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• pp.46.3-47
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• 2018

We present a general N-body exasolar system simulator in anticipation of upcoming searches for exoplanets and even exomoons by next generation telescopes such as James Webb Space Telescope. For habitable zones, traditionally defined by temperature, we here address the essential problem of dynamical stability of planetary orbits. Illustrative examples are presented on P-type orbits in stellar binary systems, that should be fairly common as in Kepler 16b. Specific attention is paid to reduced orbital lifetimes of exoplanets in the habitable zone by the stellar binary, that is propoesed by Maurice van Putten (2017). Especially, we focused on a classic work of complex three-body problem that is well known by Dvorak(1986). We charge his elliptic restricted three-body problem to extend unrestricted three-body problem to look into dynamical motions in view of circumbinary planet, furthermore, we suggest that opposite angular orientation of the planet is relative to the stability of orbits. In here, counter-rotation case is relatively more faster than co-rotation case for being stable. As a result, we find that various initial conditions and thresholds to approach dynamical stability and unstability with unexpectable isolated islands over enormous parameter space. Even, superkeplerian effect of binary is important to habitability of the exoplanet and we can verify that superfaster binary doesn't effect on th planet and increases survivality of planet around the binary.

• 천문학회보
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• 제36권2호
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• pp.140.2-140.2
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• 2011

We present high-resolution radial velocity (RV) measurements of K2 giant HD 66141 from December 2003 to January 2011 using the fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) at Bohyunsan Optical Astronomy Observatory (BOAO). We find that the RV measurements for HD 66141 exhibit a periodic variation of 480 days with a semi-amplitude of 146 m/s. We do not find the correlation between RV variations and a chromospheric activity indicator (H line). The Hipparcos photometry as well as bisector velocity span (BVS) also do not show any obvious correlations with RV variations. Thus, Keplerian motion is the most likely explanation, which suggests that the RV variations arise from an orbital motion. Assuming a possible stellar mass of 1.5 $M{\odot}$, for HD 66141, we obtain a minimum mass for the planetary companion of 7.4 MJup with an orbital semi-major axis of 1.4 AU, and an eccentricity of 0.07. We support that planet occurrence rate around evolved stars is more than 10 % (Dollinger et al. 2009) as well as more massive stars do form significantly more massive planetary companions (Johnson et al. 2007; Lovis & Mayor 2007; Dollinger et al. 2009).

• 천문학회지
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• 제47권2호
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• pp.69-76
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• 2014

We report the detection of an exoplanet candidate in orbit around ${\sigma}$ Persei from a radial velocity (RV) survey. The system exhibits periodic RV variations of $579.8{\pm}2.4$ 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 ${\sigma}$ 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 $2.25{\pm}0.5$ $M_{\odot}$, we obtain a minimum planetary companion mass of $6.5{\pm}1.0$ $M_{Jup}$, with an orbital semi-major axis of $1.8{\pm}0.1$ AU, and an eccentricity of $0.3{\pm}0.1$ around ${\sigma}$ Per.

• 천문학논총
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• 제30권2호
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• pp.295-296
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• 2015

This study deals with the generalization of the Elliptic Restricted Three-Body Problem (ER3BP) by considering the effects of radiation and oblate spheroid primaries. This may illustrate a gas giant exoplanet orbiting its host star with eccentric orbit. In the three dimensional case, this generalization may possess two additional equilibrium points ($L_{6,7}$, out-of-plane). We determine the existence of $L_{6,7}$ in ER3BP under the effects of radiation (bigger primary) and oblateness (small primary). We analytically derive the locations of $L_{6,7}$ and assume initial approximations of (${\mu}-1$, ${\pm}\sqrt{3A_2}$), where ${\mu}$ and $A_2$ are the mass parameter and oblateness factor, respectively. The fixed locations are then determined. Our results show that the locations of $L_{6,7}$ are periodic and affected by $A_2$ and the radiation factor ($q_1$).

• 천문학회보
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• 제46권2호
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• pp.78.1-78.1
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• 2021

A Lunar observatory not only provides ideas and experiences for space settlements from the Moon to Mars, but also puts the telescope in an optimal position to compete with space telescopes. Earth observation on the Moon's surface has the advantage of no atmospheric scattering or light pollution and is a stable fuel-free observation platform, allowing all longitude and latitude of the Earth to be observed for a month. Observing the entire globe with a single observation instrument, which has never been attempted before, and calculating the global albedo will significantly help predict the weather and climate change. Spectropolarimetric observations can reveal the physical and chemical properties of the Earth's atmosphere, track the global distribution and migration path of aerosols and air pollutants, and can also help detect very small space debris of which the risk has increased recently. In addition, the zodiacal light, which is difficult to observe from Earth, is very easy to observe from the lunar observatory, so it will be an opportunity to reveal the origin of the solar system and take a step closer to understanding the exoplanet system. In conclusion, building and developing a lunar observatory will be a groundbreaking study to become the world's leader that we have never tried before as a first step in expanding human experience and intelligence.

• 천문학회지
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• 제43권3호
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• pp.75-93
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• 2010

We present the characteristics of the Seoul National University 4k Camera (SNUCAM) and report its performance on the 1.5m telescope at the Maidanak observatory in Uzbekistan. SNUCAM is a CCD camera with a pixel scale of 0.266" in $4096{\times}4096$ format, covering $18.1'{\times}18.1'$ field of view on the 1.5m. The camera is currently equipped with Bessell UBVRI, $H{\alpha}$, SDSS ugriz, and Y-band filters, allowing us to carry out a variety of scientific programs ranging from exoplanet studies to survey of quasars at high redshift. We examine properties of SNUCAM such as the bias level and its temporal variation, the dark current, the readout noise, the gain, the linearity, the fringe patterns, the amplifier bias, and the bad pixels. From our observations, we also constructed the master fringe frames in I-, z-, and Y-band. We outline some of the current scientific programs being carried out with SNUCAM, and demonstrate that SNUCAM on the 1.5m can deliver excellent images that reach to the $5-{\sigma}$ detection limits of R~25.5 mag and z~22.7 mag in 1 hour total integration.

• 천문학회보
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• 제35권2호
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• pp.65.2-65.2
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• 2010

We present four new transits of the planetary system TrES-3 observed between 2009 May and 2010 June. Among those, the third transit by itself indicates possible evidence for brightness disturbance, which could originate from a starspot or an overlapping double transit. A total of 107 transit times, including our measurements, were used to determine the improved ephemeris with a transit epoch of $2454185.910950\pm0.000073$ HJED (Heliocentric Julian Ephemeris Date) and an orbital period of $1.30618698\pm0.00000016$ d. We analyzed the transit light curves using the JKTEBOP code and adopting the quadratic limb-darkening law. In order to derive the physical properties of the TrES-3 system, the transit parameters are combined with the empirical relations from eclipsing binary stars and stellar evolutionary models, respectively. The stellar mass and radius obtained from a calibration using $T_{eff}$, log $\rho$ and [Fe/H] are in good agreement with those from the isochrone analysis within the uncertainties. We found that the exoplanet TrES-3b has a mass of $1.93\pm0.07\;M_{Jup}$, a radius of $1.30\pm0.04\;R_{Jup}$, a surface gravity of $28.2\pm1.1\;m\;s^{-1}$, a density of $0.82\pm0.06\;\rho_{Jup}$, and an equilibrium temperature of $1641\pm23K$.

• 천문학회보
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• 제43권1호
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• pp.42.1-42.1
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• 2018

Deep Ecliptic Patrol of the Southern Sky (DEEP-South) observation is being made during the off-season for exoplanet survey, using Korea Microlensing Telescope Network (KMTNet). An optimal combination of its prime focus optics and the 0.3 billion pixel CCD provides a four square degrees field of view with 0.4 arcsec/pixel plate scale which is also best suited for small body studies. Normal operation of KMTNet started in October 2015, and a significant portion of the allocated telescope time for DEEP-South is dedicated to targeted observation, Opposition Census (OC), of near-Earth asteroids for physical and taxonomic characterization. This is effectively achieved through multiband, time series photometry using Johnson-Cousins BVRI filters. Uninterrupted monitoring of the southern sky with KMTNet is optimized for spin characterization of a broad spectrum of asteroids ranging from the near-Earth space to the main-belt, including binaries, asteroids with satellites, slow/fast- and non-principal axis-rotators, and thus is expected to facilitate the debiasing of previously reported lightcurve observations. Our software subsystem consists of an automated observation scheduler, a pipelined data processing system for differential photometry, and an easy-to-use lightcurve analysis toolkit. Lightcurves, spin periods and provisional determination of class of asteroids to which the lightcurve belongs will be presented, using the dataset from first year operation of KMTNet. Our new taxonomic classification scheme for asteroids will also be summarized.

• 천문학회보
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• 제41권1호
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• pp.56.2-56.2
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• 2016

We present a multi-aperture photometry pipeline for DEEP-South (Deep Ecliptic Patrol of the Southern Sky) time-series data, written in C. The pipeline is designed to do robust high-precision photometry and calibration of non-crowded fields with a varying point-spread function, allowing for the wholesale search and characterization of both temporal and spatial variabilities. Our time-series photometry method consists of three parts: (i) extracting all point sources with several pixel/blind parameters, (ii) determining the optimized aperture for each source where we consider whether the measured flux within the aperture is contaminated by unwanted artifacts, and (iii) correcting position-dependent variations in the PSF shape across the mosaic CCD. In order to provide faster access to the resultant catalogs, we also utilize an efficient indexing technique using compressed bitmap indices (FastBit). Lastly, we focus on the development and application of catalog-based searches that aid the identification of high-probable single events from the indexed database. This catalog-based approach is still useful to identify new point-sources or moving objects in non-crowded fields. The performance of the pipeline is being tested on various sets of time-series data available in several archives: DEEP-South asteroid survey and HAT-South/MMT exoplanet survey data sets.

• 천문학회보
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• 제41권1호
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• pp.55.1-55.1
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• 2016

Near Earth Asteroid (NEA) population has attracted keen attention not only from the scientific community but from the general public ever since their terrestrial impact risk achieved wide recognition. Potentially Hazardous Asteroids (PHAs), the subset of NEAs, recently became the center of interest of planetary defense folks and mining industry due to their proximity to, and the potential effects on planet Earth. However, we have long been ignorant about either the physical properties or dynamical source regions of individual objects. For instance, their rotational periods are only known for five percent of the total population (The NEA Database of DLR, updated on Feb 2016). The primary scientific objective of DEEP-South (DEep Ecliptic Patrol of the Southern sky) is to physically characterize 70 percent of km-class PHAs until 2019. In order to achieve this goal, we implemented an observation mode so-called "OC (Opposition Census)" targeting objects around opposition. OC observations were conducted during the period between Feb 2015 and Mar 2016, at CTIO in early periods, and at three KMTNet stations (CTIO, SSO and SAAO) since late July 2015, excluding the "bulge season" when the telescope time is exclusively used for exoplanet search. We present the preliminary lightcurves of 66 PHAs and 59 NEAs that we obtained during the OC runs.