• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2006년도 한국우주과학회보 제15권1호
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• pp.69-69
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• 2006

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2010년도 한국우주과학회보 제19권1호
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• pp.32.1-32.1
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• 2010

The BVR CCD observations of the solar-type contact binary GW Cephei, known as very active dynamically and photometrically, has been made for 20 nights from Nov. 03, 2008 to Dec. 31, 2008 with 1-m reflector of Jincheon station of Chungbuk National University Observatory. A total of 2035 measurements (B: 647, V: 722, R: 666) were obtained to secure new multi-color light curves. From our observations fifteen times of minimum light were newly determined. In this paper both a new period study and an intensive light synthesis were made. Our results will be compared and discussed with the latest thorough studies of the system by Lee et al. (2010).

• Journal of Astronomy and Space Sciences
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• 제11권2호
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• pp.185-195
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• 1994

우리는 충북대학교가 보유하고 었는 $1024\times1024$ pixel의 CCD 카메라를 이용하여 식변광성 U Cep를 1993년 1월 11-12일에 측광관측하였다. 이날 얻은 총 62개의 관측점을 가지고 제1극심 부근의 광도곡선을 완성하여 JD Hel 2448999.7274의 극심 시각을 결정하였다. 한편 1993년 10월 21-22일에 미국 네브라스카 대학의 Behlen 천문대에서 변광성 GW Cep와 V700 Cyg를 CCD 측광관측하여 총 168개의 관측점을 만들었다. 이들 자료를 가지고 광도곡선들을 완성하였고, GW Cep의 광도극심 시각 JD Hel 2449282.8485와 V700 Cyg의 광도극심 시각 JD Hel 2449282.7979을 각각 결정하였다. Behlen천문대의 CCD 관측방법과 충북대의 관측방법의 장단점을 비교하고 충북대 관측 방법의 개선을 위해 노출후 램에 기억되어 있는 CCD화상으로부터 직접 필요한 부분의 밝기만을 측정하고 이를 저장하는 방식의 개념을 제시하였다.

• Journal of Astronomy and Space Sciences
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• 제27권2호
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• pp.89-96
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• 2010

BVR CCD observations of GW Cep were made on 15 nights in November through December 2008 with a 1-m reflector at the Jincheon station of the Chungbuk National University Observatory. Nineteen new times of minimum lights for GW Cep were determined and added to a collection of all other times of minima available to us. These data were then intensively analyzed, by reference to an O-C diagram, to deduce the general form of period variation for GW Cep. It was found that the O-C diagram could be interpreted as presenting two different forms of period change: an exclusively quasi-sinusoidal change with a period of 32.6 years and an eccentricity of 0.10; and a quasi-sinusoidal change with a period of 46.2 years and an eccentricity of 0.36 superposed on an upward parabola. Although a final conclusion is somewhat premature at present, the latter seems more plausible because late-type contact binaries allow an inter-exchange of both energy and mass between the component stars. The quasi-sinusoidal characteristics were interpreted in terms of a light-time effect due to an unseen tertiary component. The minimum masses of the tertiary component for both cases were calculated to be nearly the same as the $0.23-0.26M\;{\odot}$-ranges which is hardly detectable in a light curve synthesis. The upward parabolic O-C diagram corresponding to a secular period increase of about $4.12{\times}10^{-8}\;d/yr$ was interpreted as mass being transferred from the lesser to more massive component. The transfer rate for a conservative case was calculated to be about $2.66\;{\times}\;10^{-8}\;M_{\odot}/yr$ which is compatible with other W UMa-type contact binaries.