• Journal of Astronomy and Space Sciences
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• 제15권1호
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• pp.83-90
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• 1998

Svechnikow & Kuznetsova (1990)의 Catalogue of Approximate Photometric and Absolute Elements of Eclipsing Variable로 부토 3780개의 식 쌍성들을 이용하여 식 쌍성의 질량-궤도 각 운동량과의 상관 관계를 조사하였다. 그 결과 쌍성이 진화하는 동안 궤도 각 운동량이 보전되지 못하며, 비록 일정한 값을 갖지는 않지만 점진적으로 분리형에서 준분리 형으로 그리고 접촉형으로 진화할수록 그 값이 감소하는 것으로 나타났다.

• Journal of Astronomy and Space Sciences
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• 제29권1호
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• pp.69-77
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• 2012

This report describes the inception, development and extensive use over 30 years of elliptical polarimeters at the University of Pennsylvania. The initial Mark I polarimeter design utilized oriented retarder plates and a calcite Foster-Clarke prism as the analyzer. The Mark I polarimeter was used on the Kitt Peak 0.9 m in 1969-70 to accomplish a survey of approximately 70 objects before the device was relocated to the 0.72 m reflector at the Flower and Cook Observatory. Successive generations of automation and improvements included the early-80's optical redesign to utilize a photoelastic modulated wave plate and an Ithaco lock-in amplifier-the photoelastic modulating polarimeter. The final design in 2000 concluded with a fully remote operable device. The legacy of the polarimetric programs includes studies of close binaries, pulsating hot stars, and luminous late-type variables.

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

• 천문학회보
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• 제41권1호
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• pp.68.1-68.1
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• 2016

Binary black hole mergers are one of the important candidate of gravitational wave (GW) emission. Recently a successful GW observation was done by LIGO team, but it is still uncertain how many GW signals will be observable. In this research, we perform simplified N-body simulations containing three mass components, ordinary stars with two kind of stellar mass black holes. Various BH compositions are tested to investigate the effect of BH mass function on binary formation rate. As a result, we find the binary formation rate is not much affected by BH mass function and always around 30 %, but the detectable merging binaries are largely depend on higher mass BH population.

• 천문학회지
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• 제51권6호
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• pp.171-183
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• 2018

To celebrate the tenth anniversary since the launch of Fermi Gamma-ray Space Telescope, we take a retrospect to a series of breakthroughs Fermi has contributed to pulsar astronomy in the last decade. Apart from significantly enlarging the population of ${\gamma}$-ray pulsars, observations with the Large Area Telescope onboard Fermi also show the population is not homogeneous. Instead, many classes and sub-classes have been revealed. In this paper, we will review the properties of different types of ${\gamma}$-ray pulsars, including radio-quiet ${\gamma}$-ray pulsars, millisecond pulsars, ${\gamma}$-ray binaries. Also, we will discuss the prospects of pulsar astronomy in the high energy regime.

• 천문학회보
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• 제44권1호
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• pp.58.1-58.1
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• 2019

Gravitational-wave (GW) sources for the next decades would be in majority binaries consisting of neutron stars and/or black holes reside in the extragalactic environment. For example, GW170817 was the first extragalactic neutron star - neutron star binary found by GW observations and it was proved the power of multi-messenger astronomy (MMA) including the KMTNet observations. With the ever increased sensitivity, the $3^{rd}$ observation run (O3) led by the advanced LIGO and advanced Virgo this year aims to search for more 'standard' populations as well as 'exotic' ones expected by stellar evolution. I will present highlights of on-going efforts by researchers in Korea and those in abroad for estimating physical parameters of a source. Mass, spin, distance, and location are prerequisite information to constrain theoretical understanding of the source formation and evolution. Furthermore, these information are to be shared with the international community for follow-up multi-messenger observations. I will present the observational accuracy expected for the future GW observations and discuss their implications. If time allows, I will make a few remarks on prospects of O3 with KAGRA collaborations, which many domestic researchers are closely involved in.

• Journal of Astronomy and Space Sciences
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• 제9권1호
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• pp.41-51
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• 1992

근접쌍성 AO Can과 AW Cam을 1984년의 관측 계절에 소백산 천문대의 61cm 반사 망원경으로 광전 관측하였다. 이 두별의 관측으로 부터 AO Cam의 채 1 극심시각 l개와 AW Cam익 체 1 극심시각 3 개를 각각 구하였다. 여러 문헌으로 부터 수집한 이 두 별의 극심시각들을 이용하여 최소자송법으로 A0 Cam파 AW Cam의 새로운 광도요소를 구하였다. AO Cam의 공전주기는 1980년 10월(JD 2444520) 부터 1985년 2월 (JD 2446107)까지 일정하였다. 그러나 최근에 Mullis와 Faulkner (1991)가 발표한 AO Cam의 l개의 제2극심시각 (JD 2447864. 7879)은 우리가 새로 구한 광도요소와 약 +4.6분 ( (0.0032일)의 큰 차이가 난다. AO Carn의 극심시각의 앞으로의 관측은 이 별의 공전주기 변화 연구에 중요하다. AW Cam의 공전주기는 지난 1930년대 초 이래 현재짜지 약 60년 동안 P=$0^d.77134645$로 일정하다

• 천문학회지
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• 제55권1호
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• pp.1-9
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• 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.

• 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.

• Journal of Astronomy and Space Sciences
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• 제23권4호
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• pp.311-318
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• 2006

ROTSE(Robotic Optical Transient Search Experiment) 후속관측을 통하여 W UMa형 식쌍성으로 재분류했던 변광성 중 광도곡선의 형태가 특이한 2개의 변광성에 대하여 2004년 5월 1일부터 5일간에 걸쳐 레몬산천문대 1m 망원경을 이용하여 고정밀 측광관측을 BVI 영역에서 수행하였다. W UMa형 식쌍성의 체계적인 분석을 위하여 2005년 개정한 Wilson-Devinney 쌍성코드를 사용하는 광도곡선분석 스크립트를 작성하였다. GSC2576-0319와 GSC2584-1731의 광도곡선을 분석하여 얻은 궤도경사각 (i)은 $43.^{\circ}5$와 $57.^{\circ}6$로써 비교적 낮은 값을 가지고 있으며, GSC2S84-1731의 광도곡선상 비대칭 효과를 설명하기 위하여 흑점모델을 적용하고, 이때의 흑점인자를 결정하였다.