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정장해,김천휘,김용기,Jeong, Jang-Hae,Kim, Chun-Hwey,Kim, Yong-Gi 한국우주과학회 2007 Journal of Astronomy and Space Sciences Vol.24 No.2
W UMa형 접촉쌍성 CC Com을 소백산 천문대에서 61cm 망원경과 2K CCD 카메라로 2002년 3월 3일부터 4월 3일까지 3일간 측광관측하여 총 824개의 관측점(${\Delta}B$: 206점, ${\Delta}V$: 206점, ${\Delta}R$: 206점, ${\Delta}I$: 206점)을 얻었다. 우리의 관측점으로부터 9개의 새로운 극심시각(주극심: 6개, 부극심: 3개)을 산출하였다. 2004년 Wilson-Devinney(WD) 쌍성 모형 계산 프로그램으로 우리가 얻은 새로운 BVRI 광도곡선과 발표된 이중시선속도 곡선들을 결합하여 분석함으로서 CC Com의 제 물리요소를 새롭게 산출하였다. 광도곡선에 나타난 작은 비대칭을 반성에 고온 반점 2개를 도입하여 설명하였다. A total of 824 observations (206 in ${\Delta}B$, 206 in ${\Delta}V$, 206 in ${\Delta}R$, 206 in ${\Delta}I$ for CC Com were made on 3 nights from March 3 to April 3 in 2002 using the 61cm telescope with 2K CCD camera of the Sobaeksan Optical Astronomy Observatory of KASI. From our observations 9 times of minimum light were newly determined. Combined analysis of our new BVRI light curves with the double-lined radial velocity curves of Pribulla et al. (2007) were made with the 2004 Wilson-Devinney(WD) binary model code to yield new physical parameters of the CC Com system. Small asymmetries in light curves were explained with the adoption of two hot spots on the cool secondary.
정장해,Jeong, Jang-Hae 한국과학기술단체총연합회 2001 과학과 기술 Vol.34 No.2
UFO는 '미확인물체'라는 뜻이므로 그런 물체는 우주 도처에 얼마든지 있을 수 있다. 그러나 오늘날의 과학이 갖고 있는 한계로는 외계인이 타고 온 비행체일 가능성은 거의 없다. 우주실험실, 우주정거장, 우주공장 등 연구영역을 우주로 확대해 나가고 있는 이 시점에서 우주를 향한 우리 과학자들의 자세를 한번 점검해 보아야 할 것이다.
WZ Cephei: A Dynamically Active W UMa-Type Binary Star
정장해,김천휘 한국우주과학회 2011 Journal of Astronomy and Space Sciences Vol.28 No.3
An intensive analysis of 185 timings of WZ Cep, including our new three timings, was made to understand the dynamical picture of this active W UMa-type binary. It was found that the orbital period of the system has complexly varied in two cyclical components superposed on a secularly downward parabola over about 80^y. The downward parabola, corresponding to a secular period decrease of -9.^d97 × 10^(-8) y^(-1), is most probably produced by the action of both angular momentum loss (AML) due to magnetic braking and mass-transfer from the massive primary component to the secondary. The period decrease rate of -6.^d72 × 10^(-8) y^(-1) due to AML contributes about 67% to the observed period decrease. The mass flow of about 5.16 × 10^(-8) M_⊙ y^(-1) from the primary to the secondary results the remaining 33% period decrease. Two cyclical components have an 11.^y8 period with amplitude of 0.^d0054 and a 41.^y3 period with amplitude of 0.^d0178. It is very interesting that there seems to be exactly in a commensurable 7:2 relation between their mean motions. As the possible causes, two rival interpretations (i.e., light-time effects (LTE) by additional bodies and the Applegate model) were considered. In the LTE interpretation, the minimum masses of 0.30 M_⊙ for the shorter period and 0.49 M_⊙ for the longer one were calculated. Their contributions to the total light were at most within 2%, if they were assumed to be main-sequence stars. If the LTE explanation is true for the WZ Cep system, the 7:2 relation found between their mean motions would be interpreted as a stable 7:2 orbit resonance produced by a long-term gravitational interaction between two tertiary bodies. In the Applegate model interpretation, the deduced model parameters indicate that the mechanism could work only in the primary star for both of the two period modulations, but could not in the secondary. However, we couldn't find any meaningful relation between the light variation and the period variability from the historical light curve data. At present, we prefer the interpretation of the mechanical perturbation from the third and fourth stars as the possible cause of two cycling period changes.