• 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.

• 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
• /
• 제55권1호
• /
• pp.1-9
• /
• 2022

We present the photometric properties of V608 Cas from detailed studies of light curves and eclipse timings. The light curve synthesis indicates that the eclipsing pair is an overcontact binary with parameters of ∆T = 155 K, q = 0.328, and f = 26%. We detected the third light ℓ₃, which corresponds to about 8% and 5% of the total systemic light in V and R bands, respectively. Including our 6 timing measurements, a total of 38 times of minimum light were used for a period study. It was found that the orbital period of V608 Cas has varied in some combination of an upward parabola and two periodic variations. The continuous period increase with a rate of +3.99 × 10^-7 d yr^-1 can be interpreted as a mass transfer from the secondary component to the primary star at a rate of 1.51 × 10^-7 M_⊙ yr^-1. The periods and semi-amplitudes of the two periodic variations are about P₃ = 16.0 yr and P₄ = 26.3 yr, and K₃ = 0.0341 d and K₄ = 0.0305 d, respectively. The most likely explanation of both cycles is a pair of light-traveling time effects operated by the possible presence of third and fourth components with estimated masses of M₃ = 2.20 M_⊙ and M₄ = 1.27 M_⊙ in eccentric orbits of e₃ = 0.66 and e₄ = 0.52. Because the contribution of ℓ₃ is very low compared to the estimated masses of two circumbinary objects, they can be inferred as very faint compact objects.

• 천문학회보
• /
• 제35권1호
• /
• pp.49.2-49.2
• /
• 2010

We have presented the evolutionary status of four detached double line spectroscopic eclipsing binaries which are CD Tau, CM Lac, HS Hya and ZZ Boo because the component stars of these binary systems still act as a single star. We determined the absolute dimensions of these binary systems using photometric and spectroscopic solutions from analysis of light curves and radial velocity curves. Using the luminosities, effective temperatures and masses we choose evolutionary tracks of these binary systems. Finally we obtained ages and metallicity of the stars. We found that CM Lac and HS Hya are very young stars and their ages are in range of 0.15-1.05 and 0.22-1.14 Gyrs. For CD Tau and ZZ Boo, they are older than the others and their age in range of 1.95-2.95 and 1.48-1.73 Gyrs.

• 천문학논총
• /
• 제30권2호
• /
• pp.215-216
• /
• 2015

Close binary stars are so close that one component has an effect on the evolution of the other. But how do they form and evolve? This is an unsolved problem. One speculation is that the binary is a part of a hierarchical triple and its orbit shrinks due to interaction with the third component. Therefore, searching for and investigating tertiary components, especially close-in ones, in close binary stars are important for understanding their origin, as well as to test theories of star formation and stellar dynamical interaction.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
• /
• 한국우주과학회 2010년도 한국우주과학회보 제19권1호
• /
• pp.32.4-32.4
• /
• 2010

Evolution of the Cosmos (ARCSEC). We have presented the evolutionary status of seven detached double line spectroscopic eclipsing binaries which are CD Tau, CM Lac, CW CMa, HS Hya, IT Cas, KM Hya, and ZZ Boo because the component stars in the binary systems still act as a single star. We determined the absolute dimensions of the binary systems using photometric and spectroscopic solutions by analyzing of the light curves and radial velocity curves. We chose evolutionary tracks of these binary systems. Using the luminosities, effective temperatures and masses. Finally we obtained ages and metallicity of the stars.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
• /
• 한국우주과학회 2009년도 한국우주과학회보 제18권2호
• /
• pp.24.1-24.1
• /
• 2009

V994 Her(ADS 11373 AB, HIP 90483) has been recently known as a quadruple system which consists of double eclipsing and double double-lined spectroscopic binaries (Lee et al. 2008). BV CCD photometric observations of the intricate star system were made during the observing seasons from 2007 to 2008 with the 35cm reflector of the Campus station of the Chungbuk National University Observatory. From the observations a total of 10 times of minimum lights were newly determined. All timings collected, including ours, were intensively analyzed to yield new interesting findings: 1) two eclipsing binaries with the orbital periods of 2.d08326 and 1.d42001 in V994 Her system show possibly apsidal motions with different apsidal periods of 46.y4 and 15.y3, and eccentricities of 0.058 and 0.082, respectively. 2) a light-time effect with a period of 0.y93 may be possible, implying that a third-body be revolving around the binary with the orbital period of 2.d08326.

• 천문학회지
• /
• 제43권6호
• /
• pp.201-211
• /
• 2010

We present an analysis of the measurements of mid-eclipse times of V839 Oph, collected from literature sources. Our analysis indicates a period increase of $3.2{\times}10^{-7}$ day/yr. This period increase of V839 Oph can be interpreted in terms of mass transfer of rate $1.76{\times}10^{-7}M_{\odot}/yr$, from the less to the more massive component. The O - C diagram shows a damping sine wave covering two different complete cycles of 36.73 yr and 19.93 yr with amplitudes approximately equal to 0.0080 and 0.0043 day, respectively. The third cycle has to be expected to cover about 13.5 years with lower amplitude than those of the former two cycles. These unequal duration cycles show a non periodicity which may be explained as resulting from either the presence of a tertiary component to the system or cyclic magnetic activity variations due to star spots. For the later mechanism, the obtained characteristics are consistent when applying Applegate (1992) mechanism.

• Journal of Astronomy and Space Sciences
• /
• 제9권1호
• /
• pp.30-40
• /
• 1992

세 종류의 식쌍성에 대한 반사 효과를 Wilson과 Devinney의 모델과 Russell과 Merrill의 모델로 분석하였다. 반사 효과를 Wilson과 Devinney의 광도 곡선 프로그램을 이용하여 이론적인 광도 곡선에 여러가지 유형별로 나타내었다. 그후 반사효과가 나타난 이론적인 광도 곡선을 Russell과 Merrill의 방법으로 근접 효과를 보정하여 두 모델을 비교 분석하였다. 두 별의 온도 차이와 반사도의 차이가 작은 경우에만 반사 효과에 관한한 두 모델이 일치함을 보였다.

• Journal of Astronomy and Space Sciences
• /
• 제29권2호
• /
• pp.169-173
• /
• 2012

A summary is presented of what is currently known about the surface temperatures of accreting white dwarfs (WDs) detected in non-magnetic and magnetic cataclysmic variables (CVs) based upon synthetic spectral analyses of far ultraviolet data. A special focus is placed on WD temperatures above and below the CV period gap as a function of the orbital period, $P_{orb}$. The principal uncertainty of the temperatures for the CV WDs in the $T_{eff}-P_{orb}$ distribution, besides the distance to the CV, is the mass of the WD. Only in eclipsing CV systems, an area of eclipsing binary studies, which was so central to Robert H. Koch's career, is it possible to know CV WD masses with high precision.