• Bulletin of the Korean Space Science Society
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• 1992.10a
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• pp.17-17
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• 1992

As a part of the project for The Atlas of (d-C) Diagams of Eclipsing Binaries, a total of 1822 times of minimum lights for Algol distributed from 1782 to 1988 are collecte dand analyzed to investigate the period-changes of the system. An (0-C) diagram constructed shows that the orbital period of Algol has varied in complicated ways. In this paper, we would interprets these variations as the sudden changes of the periodrather than as a somewhat periodic ones. The importancy of the observations for the times of minimum lights of Algol system will be stressed.

• Journal of Astronomy and Space Sciences
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• v.15 no.1
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• pp.39-48
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• 1998

We present the results of a search for photometric variable blue straggler stars(BSSs) in the globular cluster M53. Six of 151 probable BSSs are identified as variable candidates based on the robust variable star detection technique of Welch & Stetson (1993). Most variable BSS candidates appear to occupy the instability strip in the color-magnitude deagram, and they appear to have visual light amplitudes of 0.2 mag-0.3 mag. Further observations are required, however, to resolve the natrue of variabil-ity between pulsating stars and eclipsing binaries for these variable BSS candidates.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.22.3-22.3
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• 2008

We present the results of the investigations of high dispersion spectra of two stars. These are the eclipsing binary RR Lyn, and $\rho$ Pup - the prototype of the group of pulsating variables. The spectra were obtained at 1.8 m Bohyuunsan observatory telescope, and 8.2 m VLT. We found the chemical composition. The both components of RR Lyn are Am stars (metallic line stars), but the abundance patterns of the components are not similar - the iron abundance and the abundances of other elements are surely different. For few elements the differences exceeds 1 dex. We found the abundances of 56 chemical elements in the atmosphere of $\rho$ Pup. This is one of the best stellar abundance patterns. It permits to investigate the role of the charge-exchange reactions in stellar atmospheres. These reactions can produce the abundance anomalies in the atmospheres of B-F type stars. These reactions can be one of the sources of galactic cosmic rays, and the reason of the braked rotation of A-F type chemically peculiar stars.

• Journal of Astronomy and Space Sciences
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• v.29 no.1
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• pp.63-67
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• 2012

Observations with milliarsecond resolution using the Navy Optical Interferometer have been obtained for a number of stellar systems which include high-mass binaries, eclipsing binaries, and radio stars. These observations also reveal the previously unseen companions in single-lined spectroscopic binaries via directly measured flux ratios. We will present examples of published and ongoing research efforts of these systems to illustrate how an optical interferometer contributes to our knowledge of stars, their environment, and companions. These studies include a conclusive revealing of the previously unseen companion in the single-lined binary ${\Phi}$ Herculis, the direct determination of orbital parameters in the wide and close orbits of Algol, and revealing the orbit of ${\beta}$ Lyrae with spatially resolved images of the $H{\alpha}$ emission.

• Journal of Astronomy and Space Sciences
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• v.11 no.2
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• pp.175-184
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• 1994

RI photometric observations of an extreme long period eclipsing binary star AZ Cas have been made at the Yonsei University Observatory using the 60-cm Goto reflector for three seasons from 1990 to 1993. A total of 884 observations are made for 77 nights. All the data are standardized and determined the magnitudes and colors of AZ Cas. No significant light variation at the outside eclipse phase between $0.^p54$∼$0.^p87$. RI and color curves of AZ Cas are presented.

• Journal of Astronomy and Space Sciences
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• v.6 no.2
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• pp.119-125
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• 1989

UBV observations of the primary eclipse of Algol-type long period eclipsing binary AY Persei have been successfully made using the 61-cm reflector at the Ilsan Station of Yonsei University Observatory in September and October, 1989. These light curves furnish ones to deduce following results; (1) the total duration of the eclipse lasted for about 0.066(0.78 days) with no clear evidence of the existence of the totality, (2) the depths of mid-eclipse of $0^m.91$ and $1^m.07$ for V and B, respectively, (3) two times of minimum light, JD2447820.203 and JD 2447820.200 for V and B, respectively, and (4) no period variation with the improved light elements, Min I =JD2427152.237+$11^d.776620e$, $pm$10 $pm$4 are made.

• Journal of Astronomy and Space Sciences
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• v.6 no.2
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• pp.109-117
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• 1989

A total of 266 photoelectric observations(91 in V, 93 in B, and 82 in U) for an eclipsing binary, ZZ Cnc, has been secured by using the 61-cm reflector and an uncooled iP21 photomultiplier phototube of Yonsei University Observatory during 4 years from March 1984 to May 1988. One time of minimum light, JD 2446887.534 is obtained. Although Kim et al.(1988) suggested the possibility of the period change, the present study shows that the orbital period of ZZ Cnc should be constant. According in a reasonable interpretation of the eclipse light curves. Min I = JD Hel 2446887.574+25d.5944E $pm$2 $pm$2 may be useflul as new light elements for future observations.

• Journal of Astronomy and Space Sciences
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• v.11 no.1
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• pp.21-30
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• 1994

VV Cep-type long period spectroscopic-eclipsing binary AZ Cas has been observed for five years, 1985 Oct~1990 Feb, UBV at the Ilsan Station of Yonsei University Observatory. A total of 431 observations (U=129, B=142 and V=160) are made for 86 nights. Instrumental differential UBV and B-V light curves made with these observations cover phases nearly a half of one period. There is no appreciable light variation in V but in other two passbands a gradual decrease of the brightness is clearly noticed. The loss of light in B resulted in a reddening in $\Delta(B-V)$ by + 0.06 at phases between 0.4~0.5 as compared with that of at phase ~0.1. This intrinsic reddening arouses a question why at the orbital phase of the transit of a hot star in front of a cool M supergiant the heating of the facing hemisphere of M supergiant by the strong radiation from the B stat is absent. With regard to this unusual situation we propose a hypothesis that a large amount of gas stream of low temperature ejected from the surface of M supergiant component towards the B star dominates the brightness of B star and the reflection effect.

• Journal of The Korean Astronomical Society
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• v.29 no.1
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• pp.31-41
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• 1996

We present results of time-series CCD photometry for 178 stars in the young open cluster M29 (=NGC6913). Total 1036 V-band CCD frames were collected for five nights between August 12 and September 13, 1994. The photometric precision is about 7.6 mmag for 9th-10th mag stars in M29 with exposure times of 30 seconds. From the dispersion diagram and the light curves, one detached eclipsing binary (HD194378) and two suspected variables are newly discovered. $A\;\gamma\;Cas$ type variable, V1322 Cyg, which has been known as a member of M29, did not show any light variations during the period of present observations, indicating that it passed the steady phase without the eruption during our observing runs.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.63.2-63.2
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• 2017

우리 은하에 있는 618개 이심궤도 식쌍성의 카타로그를 제작하였다. 그 이심 식쌍성들은 우리의 극심시각 database에 수록된, 또는 여러 전천 탐사 자료에서 수집된 측광 자료로부터 새롭게 결정된, 또는 우리가 직접 관측하여 얻은 약 13만개의 극심시각 자료의 식시각도 분석을 통하여 편집된 것이다. 618개의 이심 식쌍성 중에서 근성점 운동을 보이는 시스템은 모두 170개이며, 이중에서 30개의 쌍성이 근성점 운동과 광시간 효과가 동시에 일어난다. 근성점 운동을 보이는 별들의 근성점 운동 변수들을 일관된 방식으로 산출하여 카타로그에 수록하였다. 우리가 작성한 최신의 카타로그는 기존 카타로그에 비해 양과 내용에 있어 가장 방대하다. 우리 은하 근성점 운동 쌍성들과 소마제란 성운과 대마젤란 성운에서 발견된 근성점 운동 쌍성들을 모아 근성점 운동 변수들의 통계적 분포를 살펴 보았고, 그 결과들을 논의한다.