• 천문학회지
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• 제2권1호
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• pp.23-32
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• 1969

The photometric orbital elements of the eclipsing variable, RZ Pyxidis, are derived by means of Fourier series from photoelectric observations which were made by Michel Breger (1964). Physical dimensions and a model of the system are suggested here.

• 천문학회보
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• 제25권1호
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• pp.43-43
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• 2000

• 천문학논총
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• 제28권3호
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• pp.83-93
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• 2013

NGC 6871을 중심으로 한 Cyg OB3 성협 영역에 대한 변광성 탐사로부터 Paper I에 이어 27개의 식쌍성과 19개의 장주기형 불규칙 변광성을 찾았다. 이 중에서 5개를 제외한 나머지는 모두 새로 발견한 것이다. 27개의 식쌍성 중에서 20개는 주기와 변광진폭 등을 구하였으며, 나머지 7개는 모두 EA형 식쌍성으로 보이지만 관측자료의 부족으로 주기를 결정하지는 못하였다. 주기를 구한 20개의 식쌍성 중에서 주극소의 깊이를 확실하게 구하지 못한 V27를 제외한 V와 B등급의 변광진폭비 $A_V/A_B$가 0.88로서 Paper I의 ${\delta}$ Scuti형 변광성의 결과를 이용한 0.72와 뚜렷이 구분된다. EW형 식쌍성 만을 이용할 경우 변광진폭비는 0.92로 더 뚜렷이 구분되었다. 19개의 장주기형 불규칙 변광성은 주기가 너무 길고, 또한 비주기성 변광성으로 보이므로 주기를 얻지는 못하고, 밝기 변화만 알 수 있었다. 이 연구에서 찾은 변광성은 V등급이 9.05등급부터 16.47등급까지 분포하며, 변광진폭이 클 경우 16.5등급까지도 변광 여부를 확인할 수 있었다.

• Journal of Astronomy and Space Sciences
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• 제20권2호
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• pp.143-152
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• 2003

식쌍성 극심시각의 체계적인 측광관측을 위하여 충북대학교 교내에 소형 반자동 망원경 관측시스템을 구축하였다. 이 시스템은 Paramount GT-1100s 독일식 마운트와 Celestron 14 광학계, 그리고 SBIG ST-8 CCD 카메라로 구성되었다. 한편, 관측시스템의 제어는 OBSTOOL이라는 소프트웨어에 의하여 이루어지는데, 이는 상용소프트웨어인 The Sky와 MaximDL에서 지원하는 COM(Component Object Model)을 이용하여 망원경과 CCD 카메라를 제어하도록 개발하였다. 이 시스템은 광전관측방법과 유사하게 망원경을 변광성, 비교성, 검토성 등으로 이동시키며 관측을 수행한다. 또한, 효율적인 자료처리를 위하여 작성한 Perl 스크립트로 관측 자료를 날짜별, 관측시야별, 필터별로 분류하고, IRAF소프트웨어를 이용하여 관측 영상의 전처리작업 등을 수행하도록 하였다. 또한, 이 시스템으로 관측한 식쌍성들의 식부근 광도곡선을 제시한다.

• 천문학회지
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• 제53권2호
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• pp.43-48
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• 2020

We report an analysis of two poorly studied eclipsing binary stars, GSC 04396-00605 and GSC 04395-00485 (recently named V455 Dra and V454 Dra, respectively). Photometric data of the two stars were obtained using the 1-m Korean telescope of the LOAO operated by KASI while monitoring the cataclysmic variable DO Dra in the frame of the Inter-Longitude Astronomy (ILA) project. We derived periods of 0.434914 and 0.376833 days as well as initial epochs JD 2456480.04281 and JD 2456479.0523, respectively, more accurate than previously published values by factors 9 and 6. The phenomenological characteristics of the mean light curves were determined using the New Algol Variable (NAV) algorithm. The individual times of maxima/minima (ToM) were determined using the newly developed software MAVKA, which outputs accurate parameters using "asymptotic parabola" approximations. The light curves were approximated using phenomenological and physical models. In the NAV algorithm, the phenomenological parameters are well determined. We derived physical parameters using the Wilson-Devinney model. In this model, the best-fit parameters are highly correlated, thus some of them were fixed to reasonable values. For both systems, we find evidence for the presence of a cool spot and estimate its parameters. Both systems can be classified as overcontact binaries of EW type.

• 천문학회지
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• 제37권4호
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• pp.143-149
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• 2004

We present photometric results for four new variable stars discovered in the vicinity of the ZZ Ceti-type pulsating white dwarf BR Cam. Observations were performed on 5 nights in November 2003 using the 1.8m telescope at Bohyunsan Optical Astronomy Observatory with no filter, on 3 nights in December 2003 using the 0.61m telescope at Sobaeksan Optical Astronomy Observatory with V, I filters, and on 3 nights in October 2004 using the 1.0m telescope at Mt. Lemmon Optical Astronomy Observatory with V, I filters. We estimated their periods from the phase-match technique for one eclipsing binary and the multiple frequency analysis for three pulsating stars. By considering the light curve shape, period and amplitude difference between two passbands, we classified the objects by their variability types as follows: V1 (USNO-A2.0 1425-05691757) is a W UMa-type eclipsing binary with an orbital period of $0^d.4641$; V2 (USNO-A2.0 1425-05703335) is a multi-periodic $\delta$ Set-type pulsating star with a dominant period of $0^d.0649$; V3 (USNO-A2.0 1425-05699659) is also a $\delta$ Set-type pulsating star with a period of $0^d.1408$; and V 4 (USNO-A2.0 1425-05707705) is a RR Lyr-type pulsating star with a period of $0^d.2643$.

• 천문학회보
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• 제41권1호
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• pp.41.1-41.1
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• 2016

We present the physical properties of KIC 6220497 exhibiting multiperiodic pulsations from the Kepler photometry. The light curve synthesis represents that the eclipsing system is a semi-detached Algol with a mass ratio of q=0.243, an orbital inclination of i=77.3 deg, and a temperature difference of ${\Delta}T=3,372K$, in which the detached primary component fills its Roche lobe by ~87% and is about 1.6 times larger than the lobe-filling secondary. To detect reliable pulsation frequencies, we analyzed separately the Kepler light curve at the interval of an orbital period. Multiple frequency analyses of the eclipse-subtracted light residuals reveal 32 frequencies in the range of $0.75-20.22d^{-1}$ with semi-amplitudes between 0.27 and 4.55 mmag. Among these, four frequencies ($f_1$, $f_2$, $f_5$, $f_7$) may be attributed to pulsation modes, while the other frequencies can be harmonic and combination terms. The pulsation constants of 0.16-0.33 d and the period ratios of $P_{pul}/P_{orb}=0.042-0.089$ indicate that the primary component is a ${\delta}$ Sct pulsating star in p modes and, thus, KIC 6220497 is an oscillating eclipsing Algol (oEA) star. The dominant pulsation period of about 0.1174 d is considerably longer than the values given by the empirical relations between the pulsational and orbital periods. The surface gravity of log $g_1=3.78$ is significantly smaller than those of the other oEA stars with similar orbital periods. The pulsation period and the surface gravity of the pulsating primary demonstrate that KIC 6220497 would be the more evolved EB, compared with normal oEA stars.

• 천문학논총
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• 제30권2호
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• pp.175-178
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• 2015

Due to the lack of an accretion disk in a polar (magnetic cataclysmic variable, MCV), the material transferred from the secondary is directly accreted onto the white dwarf, forming an accretion stream and a hot spot on the white-dwarf component. During the eclipses, different light components can be isolated. Therefore, the monitoring of eclipsing polars could provide valuable information on several modern astrophysical problems, e.g., CVs as planetary hosting stars, mass transfer and mass accretion in CVs, and the magnetic activity of the most rapidly rotating cool dwarfs. In the past five years, we have monitored about 10 eclipsing polars (e.g., DP Leo and HU Aqr) using several 2-m class telescopes and about 100 eclipse profiles were obtained. In this paper, we will introduce the progress of our research group at YNOs. The first direct evidence of variable mass transfer in a CV is obtained and we show that it is the dark-spot activity that causes the mass transfer in CVs. Magnetic activity cycles of the cool secondary were detected and we show that the variable mass transfer is not caused by magnetic activity cycles. These results will shed light on the structure and evolution of close binary stars (e.g., CVs and Algols).

• 천문학논총
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• 제30권2호
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• pp.219-221
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• 2015

We present our recent observations of SDSS J102102.25+174439.9, a new eclipsing white dwarf - main sequence WDMS binary with an orbital period of 0.14 days. This system belongs to the post common-envelope binary group as shown by the spectrum from the Sloan Digital Sky Survey. We obtained our data using the ULTRASPEC instrument installed on the 2.4-m telescope at the Thai National Observatory (TNO). Our multi-band observations reveal an unusual and persistent drop in brightness after the primary eclipse. These dips, which appear to show variations in amplitude, also have a complex shape that changes within days. Dips in WDMS systems have been observed on only one other occasion, in the light curve of QS Vir prior to the eclipse of the white dwarf. The dips in SDSS J1021+1744 are unique because they are present at different wavelengths and they occur approximately at similar phases. Hosting a DA white dwarf and an M4 companion star, this system is known to be the only WDMS to show these kind of dips in its light curve. It is possible that these dips are caused by ejected materials from an active companion star, such as in QS Vir. The light curve in the g' filter exhibits deep and narrow features, implying that the material which passes in front of the white dwarf in SDSS J1021 must be dense and small in size. Furthermore, we try to constrain the stellar and orbital parameters of SDSS J1021+1744 using the Binary Maker 3 software. We use g' and r' data for our light curve analysis to have a better approximation for the red dwarf star.

• 천문학회보
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• 제44권1호
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• pp.84.2-84.2
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• 2019

We present the absolute properties of the double-lined eclipsing binary KIC 6206751 exhibiting multiperiodic pulsations. The Kepler light curve of this system was simultaneously solved with the previously published radial-velocity data. The results indicate that the binary star is a short-period semi-detached system with fundamental parameters of $M_1=1.66{\pm}0.04M_{\odot}$, $M_2=0.215{\pm}0.006M_{\odot}$, $R_1=1.53{\pm}0.02R_{\odot}$, $R_2=1.33{\pm}0.02R_{\odot}$, $L_1=5.0{\pm}0.6L_{\odot}$, and $L_2=0.96{\pm}0.09L_{\odot}$. We applied multiple frequency analyses to the eclipse-subtracted light residuals and detected the 42 frequencies below $2.5days^{-1}$. Among these, three independent frequencies of $f_2$, $f_3$, and $f_4$ can be identified as high-order ($38{\leq}n{\leq}40$) low-degree (l=2) gravity-mode oscillations, whereas the other frequencies may be orbital harmonics and combination terms. The ratios between the orbital frequency and the pulsation frequencies are $f_{orb}:f_{2-4}{\simeq}2:3$, which implies that the ${\gamma}$ Dor pulsations of the detached primary star may be excited by the tidal interaction of the secondary companion. The short orbital period, and the low mass ratio and $M_2$ demonstrate that KIC 6206751 is an R CMa-type star, which is most likely evolving into an EL CVn star. Of seven well-studied R CMa-type stars, our program target is the only eclipsing binary with a ${\gamma}$ Dor pulsating component.