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        검색결과 14

        2.
        2013.12 KCI 등재 SCOPUS 서비스 종료(열람 제한)
        We present the first BVRI CCD photometric observations of V345 Cas made on 22 nights during the observing seasons in 2007-2008. Our light curves, resembling those of EB-type binary stars, are analyzed with the 2003 version of the Wilson- Devinney binary code. The photometric study shows that V345 Cas is a typical semi-detached binary system with the primary star being about ΔT = 2400 K hotter, two times more massive, but only 17% larger than the secondary star being filled with it's Roche-lobe. The orbit has a relatively large inclination of about 88°. A cool spot on the secondary component is modeled to explain a small light curve asymmetry. Absolute dimensions and related radiometric parameters of the eclipsing pair are calculated and their evolutionary states are discussed with the HR diagrams of mass-radius and temperature-luminosity. A period analysis of all available times of minima, including our measurements, indicates that the orbital period may vary in a cyclical way, unfortunately the secondary period for the variation can not be uniquely determined because of lack of present timing data.
        3.
        2012.12 KCI 등재 SCOPUS 서비스 종료(열람 제한)
        Astronomical Observations at Chungbuk National University Observatory (CBNUO) with an 1 m telescope have begun since April 2008, and Near-Earth Space Survey observations also have been started since November 2010, with a 0.6 m wide field telescope developed by Korea Astronomy and Space Science Institute. To improve observational efficiency, we developed a weather monitoring system enabling automatic monitoring for the weather conditions and checking the status of the observational circumstances, such as dome status. We hope this weather monitoring system can be helpful to more than 100 Korean domestic observatories, including public outreach facilities. In this paper, we present the statistic analysis of the weather conditions collected at CBNUO for 3 years (2009- 2011) and comparisons were made for clear nights between using only humidity data and both humidity and cloud data.
        4.
        2012.06 KCI 등재 SCOPUS 서비스 종료(열람 제한)
        An intensive analysis of 148 timings of V700 Cyg was performed, including our new timings and 59 timings calculated from the super wide angle search for planets (SWASP) observations, and the dynamical evidence of the W UMa W subtype binary was examined. It was found that the orbital period of the system has varied over approximately 66y in two complicated cyclical components superposed on a weak upward parabolic path. The orbital period secularly increased at a rate of +8.7 (±3.4) × 10-9 day/year, which is one order of magnitude lower than those obtained by previous investigators. The small secular period increase is interpreted as a combination of both angular momentum loss (due to magnetic braking) and mass-transfer from the less massive component to the more massive component. One cyclical component had a 20.y3 period with an amplitude of 0.d0037, and the other had a 62.y8 period with an amplitude of 0.d0258. The components had an approximate 1:3 relation between their periods and a 1:7 ratio between their amplitudes. Two plausible mechanisms (i.e., the light-time effects [LTEs] caused by the presence of additional bodies and the Applegate model) were considered as possible explanations for the cyclical components. Based on the LTE interpretation, the minimum masses of 0.29 M⊙ for the shorter period and 0.50 M⊙ for the longer one were calculated. The total light contributions were within 5%, which was in agreement with the 3% third-light obtained from the light curve synthesis performed by Yang & Dai (2009). The Applegate model parameters show that the root mean square luminosity variations (relative to the luminosities of the eclipsing components) are 3 times smaller than the nominal value (ΔL/Lp,s ≈ 0.1), indicating that the variations are hardly detectable from the light curves. Presently, the LTE interpretation (due to the third and fourth stars) is preferred as the possible cause of the two cycling period changes. A possible evolutionary implication for the V700 Cyg system is discussed.