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1968년 ~ 2023년까지 1,187 건의 한국천문학회지를 격월간 확인하실 수 있습니다.
- The Korean Astronomical Society (The Korean Astronomical Society)
- 계간 (Quarterly)
- ISSN : 1225-4614 (ISSN : 1225-4614)
1225-4614
- DB구축현황 : 1,187건 (DB Construction : 1,187 Articles)
총 게시글 1,187건
페이지 93/119
921
- LIU HANPING
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.175-176
- 1996
- 원문 바로보기
922
- IYE MASANORI
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.371-374
- 1996
- 원문 바로보기
An updated project status review of the Japan 8m telescope, Subaru, scheduled for its first light in the second quater of 1998 atop Mauna Kea is given.
923
- YOON SO-YOON
- Journal of the Korean astronomical society = 천문학회지
- 29, n.2
- pp.119-136
- 1996
- 원문 바로보기
To examine the effect of neighboring galaxies on the gravitational lensing statistics, we performed numerical simulations of lensing by many galaxies. The models consist of a galaxy in the rich cluster like Coma, or a galaxy surrounded by field galaxies in <TEX>$\Omega_0 = 1$</TEX> universe with <TEX>$\Omega_{gal} = 0.1,\;\Omega_{gal} = 0.3\;or\;\Omega_{gal}=1.0\;,\;where\;\Omega_{gal}$</TEX> is the total mass in galaxies. Field galaxies either have the same mass or follow Schechter luminosity function and luminosity-velocity relation. Each lensing galaxy is assumed to be singular isothermal sphere (SIS) with finite cutoff radius. In most simulations, the lensing is mainly due to the single galaxy. But in <TEX>$\Omega_{gal} = 3$</TEX> universe, one out of five simulations have 'collective lensing' event in which more than two galaxies collectively produce multiple images. These cases cannot be incorporated into the simple 'standard' lensing statistics calculations. In cases where 'collective lensing' does not occur, distribution of image separation changes from delta function to bimodal distribution due to shear induced by the surrounding galaxies. The amount of spread in the distribution is from a few <TEX>$\%\;up\;to\;50\%$</TEX> of the mean image separation in case when the galaxy is in the Coma-like cluster or when the galaxy is in the field with <TEX>$\Omega_{gal} = 0.1\;or\;\Omega_{gal}=0.3.$</TEX> The mean of the image separation changes less than <TEX>$5\%$</TEX> compared with a single lens case. Cross section for multiple image lensing turns out to be relatively insensitive to the presence of the neighboring galaxies, changing less than <TEX>$5\%$</TEX> for Coma-like cluster and <TEX>$\Omega_{gal}=0.1,\;0.3$</TEX> universe cases. So we conclude that Coma-like cluster or field galaxies whose total mass density <TEX>$\Omega_{gal}<0.3$</TEX> do not significantly affect the probability of multiple image lensing if we exclude the 'collective lensing' cases. However, the distribution of the image separations can be significantly affected especially if the 'collective lensing' cases are included. Therefore, the effects of surrounding galaxies may not be negligible when statistics of lensing is used to deduce the cosmological informations.
924
- WIRAMIHARDJA SUHARDJA D.
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.265-266
- 1996
- 원문 바로보기
925
- LEE SEE-WOO
- Journal of the Korean astronomical society = 천문학회지
- 29, n.1
- pp.53-62
- 1996
- 원문 바로보기
31 white dwarfs in 10 open clusters are examined, and their maximum mass and the upper mass limit of their progenitors are obtained as <TEX>$1.22\pm0.02M_{\bigodot}\;and\;7.2\pm0.4M_{\bigodot}$</TEX> respectively, suggesting that the upper mass limit of white dwarfs is less than <TEX>8M_{\bigodot}$</TEX> The final mass of white dwarfs shows no clear correlation with the initial mass of their progenitors, and it is found that a deficient gap of initial mass exists between <TEX>$\~4\;and\;~5.2M_{\bigodot}$</TEX>. This gap seems to correspond to the mass range for carbon detonation or deflagration. The total expected numbers of white dwarfs are <TEX>$11\~22$</TEX> in Hyades with 7 known white dwarfs and 17 in Praesepe with 8 known white dwarfs. These known white dwrfs are all younger than the others in both clusters. But one known white dwarf in Pleiades is older one among <TEX>$2\~3$</TEX> expected white dwarfs.
926
- WU XUE-BING
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.231-232
- 1996
- 원문 바로보기
The local instabilities of accretion disks were extensively studied, with the considerations of radial advection, thermal diffusion and different disk geometry, dominated pressure and optical depth. Two inertial-acoustic modes in a geometrically thin, radiative cooling dominated disk depart from each other if very little advection is included. A geometrically slim, advection-dominated disk is found to be always stable if it is optically thin. However, if it is optically thick, the thermal diffusion has no effect on the stable viscous mode but has a significant contribution to enhance the thermal instability.
927
- YANAGISAWA KENSHl
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.75-76
- 1996
- 원문 바로보기
We have started multi-color imaging program of nearby galaxies since last year and present preliminary result here. We selected 12 nearby galaxies classfied from E to Sab type and observed in BVRIJHK' bands. Photomtric parameters such as isophotal diameter, axial ratio, isophotal magnitude were measured and observed colors were compared with theoritical model. We find a standard evolution model agrees well with observed results.
928
- KOZAI YOSHIHIDE
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.351-354
- 1996
- 원문 바로보기
In this paper it is explained how most of asteroids can avoid very close approach to Jupiter, to the earth for earth orbit crossing asteroids, and to Neptune for Kuiper-belt asteroids by mechanisms which work also for Neptune-Pluto system. In fact the mutual distance of the planets cannot become very small as the critical argument librates around <TEX>$180^{\circ}$</TEX> because of 2:3 mean motion resonance and the argument of perihelion of Pluto librates around <TEX>$90^{\circ}$</TEX>. And it is found that among nearly 40 Kuiper-belt asteroids discovered in recent years <TEX>$40\%$</TEX> have orbits similar to Pluto. For main-belt asteroids the distribution with respect to the semi-major axes has peculiar characteristics and the author tries to explain how their peaks and gaps are created. It is also found that <TEX>$30\%$</TEX> of 80 earth orbit crossing asteroids which have minimum perihelion distances less than 1.04AU have no chance to collide with the earth. Still <TEX>$30\%$</TEX> of them have a few probability to collide with the earth as they have dynamical characteristics of short-periodic comets.
929
- CHITRE S. M.
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.31-33
- 1996
- 원문 바로보기
The role of gravitational lenses as valuable tools for astrophysics and cosmology is highlighted.
930
- TSIOPA O. A.
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.215-216
- 1996
- 원문 바로보기
The wind-formed features observed in the early SNe spectra type II and Ia give an evidence of the existence of an ellipsoidal shell formed by the stellar wind prior to the explosion. Such non-spherical shell can occur not only at scales of parsec (the case of SN 1987 A progenitor), but at the scales of 1000 times less. Such shells can be the result of the radial pulsation. The prolate multi-shell structures are interpreted as a result of a pulsation processes with recurrent wind ejections with velocity increasing.