• Journal of Astronomy and Space Sciences
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• 제29권1호
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• pp.47-49
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• 2012

Massive binary stars lose mass by two mechanisms: jet-driven mass loss during periods of active mass transfer and by wind-driven mass loss. Beta Lyrae is an eclipsing, semi-detached binary whose state of active mass transfer provides a unique opportunity to study how the evolution of binary systems is affected by jet-driven mass loss. Roche lobe overflow from the primary star feeds the thick accretion disk which almost completely obscures the mass-gaining star. A hot spot predicted to be on the edge of the accretion disk may be the source of beta Lyrae's bipolar outflows. I present results from spectropolarimetric data taken with the University of Wisconsin's Half-Wave Spectropolarimeter and the Flower and Cook Observatory's photoelastic modulating polarimeter instrument which have implications for our current understanding of the system's disk geometry. Using broadband polarimetric analysis, I derive new information about the structure of the disk and the presence and location of a hot spot. These results place constraints on the geometrical distribution of material in beta Lyrae and can help quantify the amount of mass lost from massive interacting binary systems during phases of mass transfer and jet-driven mass loss.

• 천문학논총
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• 제32권3호
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• pp.421-438
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• 2017

Through the short-period variability survey program, we obtained time-series BV CCD images for $1.5^{\circ}{\times}1.0^{\circ}$ region around the young open cluster NGC 457. As a result, we have detected 61 variable stars including 31 new ones after checking light curves of all stars by eyes. The 61 variable stars were included 14 ${\delta}$ Scuti variable stars, a ${\beta}$ Cephei variable star, 10 variable Be and slowly pulsating B stars, 13 eclipsing binary stars, 21 semi-long periodic or slow irregular variables and an RR Lyrae variable star, respectively. Many variable B-type stars were known through a well-defined zero-age main sequence to the ${\beta}$ Cepheid region of NGC 457. Most of the variable B-type stars found this paper were known variable stars. But, 11 out of 14 ${\delta}$ Scuti variable stars were newly discovered. The new variable stars except for ${\delta}$ Scuti stars were 4 variable B-type stars, 5 eclipsing binaries and 11 semi-long periodic or slow irregular variables. We have performed frequency analysis for all ${\delta}$ Scuti stars, a ${\beta}$ Cepheid star and an RR Lyrae star.

• Journal of Astronomy and Space Sciences
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• 제13권1호
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• pp.1-8
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• 1996

CCD time series photometry was performed for two Oosterhoff type II field RR Lyrae stars, SV Eri and XX And, to construct light curves in B and V bands. The maximum light times from our observations were combined with those in the literature to construct phase shift diagrams, from which we determined the period change rates ${\beta}$. We obtained large positive period change rates for these stars, which are expected from current evolutionary models if these stars are evolving rapidly from blue to red toward the end of core helium burning phase.

• 천문학회지
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• 제38권1호
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• pp.13-16
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• 2005

We present a period analysis of the well known $\beta$ Lyrae type eclipsing binary GO Cyg $(P= 0^d .7177)$. Several new times of minimum light, recorded photoelectrically, have been gathered. Analysis of all available eclipse timings of GO Cyg has confirmed a significant period increase with rate of $2.52 {\times} 10^{-10}$ day / cycle, also new period has been estimated. New linear and quadratic ephemerides have been calculated for the system.

• Journal of Astronomy and Space Sciences
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• 제29권1호
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• pp.63-67
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• 2012

Observations with milliarsecond resolution using the Navy Optical Interferometer have been obtained for a number of stellar systems which include high-mass binaries, eclipsing binaries, and radio stars. These observations also reveal the previously unseen companions in single-lined spectroscopic binaries via directly measured flux ratios. We will present examples of published and ongoing research efforts of these systems to illustrate how an optical interferometer contributes to our knowledge of stars, their environment, and companions. These studies include a conclusive revealing of the previously unseen companion in the single-lined binary ${\Phi}$ Herculis, the direct determination of orbital parameters in the wide and close orbits of Algol, and revealing the orbit of ${\beta}$ Lyrae with spatially resolved images of the $H{\alpha}$ emission.

• Journal of Astronomy and Space Sciences
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• 제12권1호
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• pp.21-29
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• 1995

$\beta$ Lyrae형 식쌍성 AW Cam을 UBV 세파장 영역에서 광전 관측하여 얻은 UBV 광도곡선을 Wilson and Devinney 쌍성 모델의 2가지 mode( mode 2와 mode 5)로 분석하였다. 이는 Russo and Milano (1983)가 산출한 측광 질량비(q=0.21)와 Mammano et al. (1967)의 분광질량비(q=0.43)가 일치하지 않는 모순-AW Cam 계의 남아 있는 문제인-올 해결하기 위한 것이다. Mode 2로 구한 측광학적 해가 mode 5로 구한 해보다 관측된 광도곡선을 더 잘 반영하는 것으로 계산되었다. 이는AW Cam이 정상준분리형계가 아나라 분리형 쌍성계임을 제시하는 것으로 해석될 수 있다. 또한 산출한 질량비 (q=0.43)로 계산한 AW Cam계의 삼차원 로쉬 모형을 보면 가벼운 반성은 안쪽 로쉬 한계면에 잘 들어 있는 반연 더 무거운 주성이 로쉬 한계면에 거의 접촉하고 있다. 로쉬 기하, 공전주기의 일정성, 그리고 다른 측광학적 증거들로 부터 AW Cam은 Giuricin and Mardrossian (1981)이 제안한 ‘접촉이 깨진 상태’에 있는 진화된 분리형 쌍성계가 아니라, ‘접촉 상태’로 가고 있는case A 진화 상 태에 있는 덜 진화된 분리형 쌍성계로 잠정적으로 결론짓는다