• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2008년도 한국우주과학회보 제17권2호
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• pp.38.3-38.3
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• 2008

In There are inventoried 308 eclipsing systems among 1,158 multiple systems listed in Tokovinin (1997, 2007)'s multiple system catalog. Their characteristics of (O-C) variations for 83 systems among the 308 systems, which have timings of minimum lights enough to see the trends of their period changes, were investigated with the Kreiner, Kim and Nha (2001)'s recent database of times of minimum lights of eclipsing binaries. It is found that the (O-C) variations for 39 systems, corresponding to 47% of the investigated 83 systems, does not show any anticipated light-time effects (hereafter LITE) at all. Among the rest 44 systems 7 systems with apsidal motion also have a single LITE. Only 6 systems have a single LITE or double LITEs. The rest 31 systems show a secular variation superposed on a single or double or more LITEs or very complicated variation patterns. Some possible explanations for their diverse differentiation of variation are discussed.

• Journal of Astronomy and Space Sciences
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• 제29권2호
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• pp.123-129
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• 2012

The BINSYN program package, recently expanded to calculate synthetic spectra of cataclysmic variables, is being further extended to include synthetic photometry of ordinary binary stars in addition to binary stars with optically thick accretion disks. The package includes a capability for differentials correction optimization of eclipsing binary systems using synthetic photometry.

• 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).

• 천문학회보
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• 제27권2호
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• pp.42-42
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• 2002

• 천문학회보
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• 제3권
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• pp.45-51
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• 1978

• Journal of Astronomy and Space Sciences
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• 제15권1호
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• pp.83-90
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• 1998

Svechnikow & Kuznetsova (1990)의 Catalogue of Approximate Photometric and Absolute Elements of Eclipsing Variable로 부토 3780개의 식 쌍성들을 이용하여 식 쌍성의 질량-궤도 각 운동량과의 상관 관계를 조사하였다. 그 결과 쌍성이 진화하는 동안 궤도 각 운동량이 보전되지 못하며, 비록 일정한 값을 갖지는 않지만 점진적으로 분리형에서 준분리 형으로 그리고 접촉형으로 진화할수록 그 값이 감소하는 것으로 나타났다.

• 천문학논총
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• 제26권4호
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• pp.141-146
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• 2011

In the region of the open cluster M48 (NGC 2548), time-series BV CCD images were taken for 22 nights from February 28 in 2008 to March 17 in 2011. From this observation, we found 10 new variable stars. They include five eclipsing binaries, an RR Lyrae, two ${\delta}$ Scuti, and two semi-periodic and/or slow irregular type variable stars. We fail to find the member stars of the open cluster among the 10 variable stars.

• 천문학회지
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• 제48권1호
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• pp.1-7
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• 2015

The orbital period changes of the W UMa eclipsing binary AU Ser are studied using the (O-C) method. We conclude that the period variation is due to mass transfer from the primary star to the secondary one at a very low and decreasing rate $dP/dt=-8.872{\times}10^{-8}$, superimposed on the sinusoidal variation due to a third body orbiting the binary with period $42.87{\pm}3.16$ years, orbital eccentricity $e=0.52{\pm}0.12$ and a longitude of periastron passage ${\omega}=133^{\circ}.7{\pm}15$. On studying the magnetic activity, we have concluded that the Applegate mechanism failed to describe the cycling variation of the (O-C) diagram of AU Ser.

• 천문학회지
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• 제43권6호
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• pp.201-211
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• 2010

We present an analysis of the measurements of mid-eclipse times of V839 Oph, collected from literature sources. Our analysis indicates a period increase of $3.2{\times}10^{-7}$ day/yr. This period increase of V839 Oph can be interpreted in terms of mass transfer of rate $1.76{\times}10^{-7}M_{\odot}/yr$, from the less to the more massive component. The O - C diagram shows a damping sine wave covering two different complete cycles of 36.73 yr and 19.93 yr with amplitudes approximately equal to 0.0080 and 0.0043 day, respectively. The third cycle has to be expected to cover about 13.5 years with lower amplitude than those of the former two cycles. These unequal duration cycles show a non periodicity which may be explained as resulting from either the presence of a tertiary component to the system or cyclic magnetic activity variations due to star spots. For the later mechanism, the obtained characteristics are consistent when applying Applegate (1992) mechanism.

• 천문학논총
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• 제24권1호
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• pp.19-34
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• 2009

From the short-period variability survey (SPVS) in Bohyunsan Optical Astronomy Observatory, I obtained time-series BV CCD images in the region of the young open cluster M29 (NGC 6913) for 15 nights from May 30, 2008 to September 17, 2009. I observed 48 variable stars including 45 new ones. They consisted of 5 $\delta$ Scuti, a Cepheid, 16 eclipsing binaries and 24 semi-long periodic and/or slow irregular type variable stars including $\beta$ Cephei and LPB type stars. For the rest two ones, the type of variability was not defined. I also checked the variability of the 26 known variable stars listed in the GCVS. Only three ones among 26 known variable stars confirmed variability.