• 천문학회보
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• 제35권1호
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• pp.83.2-83.2
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• 2010

During the formation of cosmic web, collisionless shock waves are produced around and inside the substructures. In these shock waves electrons and ions are accelerated to such high energies that they can produce gamma rays in several ways. Many authors have studied the contribution of shock-induced radiation to the cosmic gamma-ray background. However not all the important physical processes are included in their calculation. By considering more complete physical process, we re-investigate the problem. In our model, the energy distribution of the cosmic rays (CRs) are calculated by widely accepted diffusive shock acceleration model, both primary and secondary CR electrons are included, both inverse Compton scattering and bremsstrahlung process are considered. The difference of the results are discussed.

• 천문학회보
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• 제35권2호
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• pp.35.1-35.1
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• 2010

Unlike the initial mass function, the initial size distribution of globular cluster (GC) systems is not well known. We calculate the evolution of the mass function (MF), radial distribution (RD), and size distribution (SD) of the Galactic GC system. By comparing the results from this calculation and the present-day MF, RD, and SD of the Galactic GC system, we infer the initial SD of the GC system. We find that a Gaussian distribution of the half-mass radius and a Gaussian distribution of the half-mass to Jacobi radius ratio are the best-fit initial SDs of the Galactic GC system.

• 천문학회지
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• 제31권2호
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• pp.105-108
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• 1998

We have found that the two-point correlation function of the APM clusters of galaxies has an amplitude much higher than that claimed by the APM group. As the richness limit increases from R = 53 to 80, the correlation length increases from 17.5 to 28.9 $h^{-1}Mpc$. This indicates that the richness dependence of the APM cluster correlation function is also much stronger than what the APM group has reported. The richness dependence can be represented by a fitting formula ro = 0.53dc + 0.01, which is consistent with the Bahcall's formula ro = 0.4dc. We have tried to find the possible reason for discrepancies. However, our estimates for the APM cluster correlation function are found to be robust against variation of the method of calculation and of sample definition.

• 천문학회지
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• 제29권2호
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• pp.93-105
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• 1996

We have solved the radiative transfer problem using a Sobolev approximation with an escape probability method in case of the supersonic expansion of a stellar envelope to an ambient medium. The radiation from the expanding envelope turns out to produce a P-Cygni type profile. In order to investigate the morphology of the theoretical P-Cygni type profile, we have treated $V_\infty,\;V_{sto},\;\beta$ (parameters for the velocity field), it and E(parameter for collisional effect) as model parameters. We have investigated that the velocity field and the mass loss rate affect the shapes of the P-Cygni type profiles most effectively. The secondarily important factors are $V_\infty,\;V_{sto}$. The collisional effect tends to make the total flux increased but not so much in magnitude. We have infered some physical parameters of 68 Cyg, HD24912, and $\xi$ persei such as $V_\infty,\;M$ from the model calculation, which shows a good agreenment with the observational results.

• 천문학회지
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• 제45권2호
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• pp.49-57
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• 2012

In this study, I calculate the past and future dynamical states of the Earth-Moon system by using modified Lambeck's formulae. I find that the ocean tidal effect must have been smaller in the past compared to its present amount. Even though the Moon is already in the spin-orbit synchronous rotational state, my calculation suggest that it will not be in geostationary rotational state in the next billion years or so. This is due to the associated Earth's obliquity increase and slow retardation of Earth's spin and lunar orbital angular velocities. I also attempt to calculate the precessional period of the Earth in the future. To avoid uncertainties in the time scale, the future state is described by using the Earth-Moon distance ratio as independent parameter. Effects due to solar tidal dissipation are included in all calculations.

• 천문학회보
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• 제38권1호
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• pp.56.2-56.2
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• 2013

Compact binaries are important sources of gravitational waves. They are also prime targets for long baseline laser interferometers. In this talk, we present latest progresses made in the Galactic merger rate calculations for compact binaries in the Galactic disk, with an emphasis on NS-NS binaries. For the first time, the non-recycled pulsar found in the Double Pulsar system (PSR J0737-3039B) is included in the rate calculation. We then discuss the prospects of detecting gravitational waves for Earth-based detectors such as advanced LIGO (Laser Interferometer Gravitational-wave Observatory) in US and advanced Virgo in Europe, extrapolating the Galactic rate estimates up to the detection volume of the advanced LIGO-Virgo network, Our results support the expectation that gravitational waves emitted from compact binary mergers will be detected within a decade. However, the detection rate of gravitational waves associated with NS-NS mergers is most likely to be several per year that is much smaller than what has been previously known.

• 천문학논총
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• 제4권1호
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• pp.1-15
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• 1989

A jet plasmoid model for 3C.449 has been constructed by introducing a plasma.ejecting black hole orbiting around the center of its parent cD galaxy. We examined the characteristics of the jet trajectory by varying the values of (1) orbiting radius and velocity of the black hole, (2) plasma ejection velocity, (3) size, mass and space velocity of the parent galaxy, (4) size of the galactic core and (5) the density of the intergalactic medium. In our model calculation the effect of the gravity by the parent galaxy and the ram pressure by the intergalactic medium have been taken in account. It is found that our dynamical model accounts reasonably well for the observed structure of 3C449. Our proposed model suggests that the buoyancy force near the galactic center plays an important role in the formation of the curved structure of the radio jet.

• 천문학회보
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• 제41권1호
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• pp.51.2-51.2
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• 2016

이 연구에서는 중수대명력(重修大明曆)에서 태양과 달의 운동 계산 방법에 대해 분석하였다. 중수대명력은 금(金)대의 양급(楊級)이 만든 대명력을 당대의 조지미(趙知微)가 중수한 역법으로 1281년 수시력(授時曆)이 도입되기 전까지 원(元)에서 사용되었다. 반면 조선에서는 "칠정산내편", "칠정산외편"과 더불어 일 월식 계산에 사용된 것으로 알려져 있다. 이를 위해 세종 26년(1444)에는 이순지(李純之) 등에 의해 "중수대명력"과 "중수대명력 정묘년 교식가령(丁卯年 交食假令)" 등이 편찬되었으며, "중수대명력"의 경우 "금사(金史)" 의 내용과 동일한 것으로 알려져 있다. 이 논문에서는 이들 문헌을 활용하여 중수대명력에서의 태양과 달의 운동, 특히 이들의 부등속운동 계산방법에 대해 분석하고, 이를 수시력에서의 방법과 비교 하였다.

• 천문학회보
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• 제39권1호
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• pp.82.2-82.2
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• 2014

지상에서 천체 분광관측을 하면 천체 스펙트럼에 대기 흡수선이 겹쳐 나타나기 때문에 이를 제거해주어야 한다. 대기 흡수선은 주로 적외선 영역에 많이 나타나고, 주로 H2O, O2, CO2, O3, CH4 등의 분자에 의하여 생긴다. 대기 흡수선을 제거하기 위하여 조기형 별을 관측하여 그 스펙트럼으로 천체스펙트럼을 나누어주는 방법이 널리 이용된다. 본 연구에서는 인공 흡수선 스펙트럼을 계산하여 대기 흡수선을 제거하는 방법을 소개하기로 한다. 인공 흡수선 스펙트럼 계산은 LBLRTM 코드를 이용하였으며 대기모델은 MIPAS를 채택하였다. 이렇게 계산한 인공 스펙트럼을 실제 관측된 대기 흡수선에 맞추기 위하여 가우시안 라인 프로파일을 이용하고 파장 눈금을 조정해 준다. 이 과정에서 대기 흡수선을 정밀 시선속도 측정을 위한 파장 표준으로 이용할 수 있다.

• 천문학논총
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• 제11권1호
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• pp.221-229
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• 1996

We have developed a measurement system with which harmful radio noise can be detected. It was designed to cover 1GHz band width centered at l.5GHz and 22.2GHz ($H_2O$ line).The system consists of pyramid horn antennas, receivers, equatorial tracking system, spectrum analyzer, and PC for the control of the servo and data taking. As a test of the system, the site of Taeduk Radio Astronomy Observatory (TRAO) was investigated to see if there is any harmful radio interference. It is found that in 22GHz band there is no significant radio noise, but there are identified and unidentified artificial radio signals in 1-2GHz range. However a simple calculation of radiation power shows that it is week enough not to affect the observations in TRAO.