• 한국우주과학회:학술대회논문집(한국우주과학회보)
• /
• 한국우주과학회 2008년도 한국우주과학회보 제17권2호
• /
• pp.22.3-22.3
• /
• 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.

• 천문학회지
• /
• 제37권4호
• /
• pp.143-149
• /
• 2004

We present photometric results for four new variable stars discovered in the vicinity of the ZZ Ceti-type pulsating white dwarf BR Cam. Observations were performed on 5 nights in November 2003 using the 1.8m telescope at Bohyunsan Optical Astronomy Observatory with no filter, on 3 nights in December 2003 using the 0.61m telescope at Sobaeksan Optical Astronomy Observatory with V, I filters, and on 3 nights in October 2004 using the 1.0m telescope at Mt. Lemmon Optical Astronomy Observatory with V, I filters. We estimated their periods from the phase-match technique for one eclipsing binary and the multiple frequency analysis for three pulsating stars. By considering the light curve shape, period and amplitude difference between two passbands, we classified the objects by their variability types as follows: V1 (USNO-A2.0 1425-05691757) is a W UMa-type eclipsing binary with an orbital period of $0^d.4641$; V2 (USNO-A2.0 1425-05703335) is a multi-periodic $\delta$ Set-type pulsating star with a dominant period of $0^d.0649$; V3 (USNO-A2.0 1425-05699659) is also a $\delta$ Set-type pulsating star with a period of $0^d.1408$; and V 4 (USNO-A2.0 1425-05707705) is a RR Lyr-type pulsating star with a period of $0^d.2643$.

• 천문학회지
• /
• 제51권1호
• /
• pp.1-4
• /
• 2018

We study the pseudo-synchronous orbital motion of a binary system on the main sequence. The equations of the pseudo-synchronous orbit are derived up to $O(e^4)$ where e is the eccentricy of the orbit. We integrate the equations to present their solutions. The theoretical results are applied to the evolution of the orbit and spin of the binary star Y Cygni, which has a current eccentricity of $e_0\;=\;0.142$. We tabulate our numerical results for the evolution of the orbit and spin per century. The numerical results for the semi-major axes and rotational angular velocities in the evolutional time scales of three stages (synchronization, circularization, and collapse time scale) are also tabulated. Synchronization is achieved in about $5{\times}10^3\;years$ followed by circularization lasting about $1{\times}10^5\;years$ before decaying in $2{\times}10^5\;years$.

• 천문학논총
• /
• 제22권4호
• /
• pp.141-149
• /
• 2007

Preliminary time-series observations for short-period variability survey (SPVS) were carried out using a 155mm refractor and a $2k{\times}3k$ CCD camera at Bohyunsan Optical Astronomy Observatory. We found 21 new variable stars in the $90'{\times}60'$ test field region : 9 eclipsing binary stars, $5{\delta}$ Scuti type stars, a ${\gamma}$ Doradus type star, and 6 long period variables. The observing field center is R.A. $05^h\;00^m\;00^s$, DEC. $50^{\circ}\;00'\;00"$ (J2000.0). The period and amplitude ranges for the short-period variables, i.e., ${\delta}$ Scuti stars, were 0.052day - 0.107day and 0.012mag - 0.064mag, respectively.

• 천문학논총
• /
• 제20권1호
• /
• pp.29-35
• /
• 2005

Time-series observations were carried out using a 155mm refractor and a $2k{\times}3k$ CCD camera at Bohyunsan Optical Astronomy Observatory. We found 38 new variable stars in the $2.3^{\circ}{\times}2.4^{\circ}$ region around the Cepheid variable TU Cas: 22 eclipsing binary stars, 11 ${\delta}$ Scuti type stars and an RR Lyrae star, and 4 unclassified variables.

• 천문학회지
• /
• 제44권3호
• /
• pp.97-108
• /
• 2011

The photometric light curves of the W-type W UMa eclipsing contact binary system BB Pegasi have been found to be extremely asymmetric over all the observed 63 years in all wavelengths UBVR. The light curves have been characterized by occultation primary minima. Hence, the morphology of these light curves has been studied in view of these different asymmetric degrees. The system shows a distinct O'Connell effect, as well as depth variation. A 22.96 years of stellar dark spots cycle has been determined for the system. Almost the same cycle (22.78 yr) has been found for the depth variation of MinI and MinII. We also present an analysis of mid-eclipse time measurements of BB Peg. The analysis indicates a period decrement of $5.62{\times}10^{-8}$ day/yr, which can be interpreted in terms of mass transfer at a rate of $-4.38{\times}10^{-8}M_{\odot}$/yr, from the more to the less massive component. The O - C diagram shows a damping sine wave covering two different cycles of 17.0 yr and 12.87 yr with amplitudes equal to 0.0071 and 0.0013 day, respectively. These unequal durations show a non-periodicity which may be explained as a result of magnetic activity cycling variations due to star spots. The obtained characteristics are consistent with similar chromospherically active stars, when applying the Applegate's (1992) mechanism.

• 천문학논총
• /
• 제30권3호
• /
• pp.821-832
• /
• 2015

NGC 1039 영역의 변광성 탐사로부터 7개의 ${\delta}$ Scuti형 변광성, 2개의 ${\gamma}$ Doradus형 변광성, 14개의 식쌍성 및 5개의 장지기형 불규칙 변광성을 찾았다. 이 중에서 3개를 제외한 나머지는 모두 새로 발견한 것이다. 이들 중 ${\delta}$ Scuti형 변광성 4개와 ${\gamma}$ Doradus형 변광성 2개 및 장주기형 불규칙 변광성 1개는 성단구성원일 가능성이 크다. 14개의 식쌍성 중에서 12개는 주기와 변광진폭 등을 구하였으며, 나머지 2개는 22일 관측 자료 중 하루치에서만 식 현상이 나타나서 EA형 식쌍성으로 보인다. B, V등급의 변광진폭을 같이 구한 식쌍성의 변광진폭비 $A_V/A_B$는 0.92이며, ${\delta}$ Scuti형 변광성의 결과를 이용한 0.75와 뚜렷이 구분된다. 5개의 장주기형 불규칙 변광성은 하나를 제외하고 나머지는 주기가 너무 길었고, 또한 주기성인지 알 수 없어서 밝기 변화만으로 변광성임을 알 수 있었다. 이 연구에서 찾은 변광성은 V등급이 10.84등급부터 16.30등급까지 분포하며, V등급의 변광진폭이 0.5등급 이상이면 16.3등급까지도 변광 여부를 확인할 수 있었다.

• 천문학회지
• /
• 제48권1호
• /
• pp.1-7
• /
• 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.

• Journal of Astronomy and Space Sciences
• /
• 제22권3호
• /
• pp.223-232
• /
• 2005

질량비가 작은 접촉쌍성 V410 Aur과V776 Cas를 소백산천문대의 61cm망원경에 2K CCD 카메라를 부착하여 측광 관측을 하였으며, 그 결과 이 별들의 새로운 3색(BVR)의 완전한 광도곡선을 얻었다. 새로운 광도곡선과 이미 발표된 분광관측으로부터 WD모델을 이용하여 이 두 별의 궤도요소와 절대 물리량을 얻었다. V410 Aur과 V776 Cas를 포함한 절대물리량이 잘 알려진 19개의 질량비가 작은 접촉쌍성들의 진화 상태를 조사하였다. 그 결과 질량비가 작은 접촉쌍성의 주성은 대부분 TAMS상에 놓이며 반성은 ZAMS 아래 놓이고 있음을 재확인하였다.

• 천문학논총
• /
• 제15권spc1호
• /
• pp.147-151
• /
• 2000

Symbiotic stars, believed to be binary systems of a mass-losing giant and a white dwarf with an emission nebula, are known to exhibit very broad wings around Hex that extend to $\~10^3km\;s^{-1}$. The wing formation mechanism is not a settled matter and recently Lee (2000) proposed that Raman scattering of Ly$\beta$ by neutral hydrogen is responsible for the broad H$\alpha$ wings. In this model, it is predicted that. the Hex wings will be polarized depending on the geometric and kinematic distribution of the scatterers relative to the UV emission region. In this paper, we investigate the polarization of Hex wings in symbiotic stars. Noting that many symbiotic stars possess bipolar nebular morphology, we assume that the distribution of neutral scatterers follows the similar pattern with a receding velocity of several tens of km $s^{-1}$ that mimics the expansion of the neutral envelope of the nebula. It is found that the red wing is more strongly polarized than the blue and main part and that the polarization direction is along the equatorial plane. We obtain a typical degree of polarization $\~10$ percent, however, it varies depending on the detailed distribution of H I scatterers We conclude that spectropolarimetry will provide very important information on the origin of the Hex wings.