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- The Korean Astronomical Society (The Korean Astronomical Society)
- 계간 (Quarterly)
- ISSN : 1225-4614 (ISSN : 1225-4614)
1225-4614
- DB구축현황 : 1,211건 (DB Construction : 1,211 Articles)
총 게시글 1,211건
페이지 105/122
1041
- MINH Y. C.
- Journal of the Korean astronomical society = 천문학회지
- 26, n.2
- pp.99-101
- 1993
- 원문 바로보기
We have searched for the 2 mm transitions of <TEX>$H_2COH^+(2_{02}-1_{01})$</TEX> and <TEX>$H_2\;^{13}CO(2_{02} - 1_{01},\; 2_{12}-1_{11},\;and\;2_{11}-1_{10})$</TEX> toward the dense interstellar molecular clouds Orion A, TMC-1 and L134N using the FCRAO 14 m telescope. None of the transitions have been detected except the <TEX>$H_2\;^{13}CO$</TEX> transitions toward Orion-KL. We set upper limits for the abundances of the protonated formaldehyde ion <TEX>$(H_2COH^+)$</TEX>, which are close to the abundances expected from ion-molecule chemistry.
1042
- Hong, S.S.
- 天文學會誌 = The journal of the Korean Astronomical Society
- 25, n.1
- pp.23-46
- 1992
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The electrical, mechanical and optical capabilities have been tested of the microdensitometer PDS 1010GMS at the Korea Astronomy Observatory. The highest stage of scan speed 255 csu (conventional speed unit) is measured to be 47 mm/s. At this speed the position is displaced by <TEX>$4{\mu}m$</TEX> to the direction of scanning and the density is underestimated by <TEX>$0.4{\sim}0.7D$</TEX>. Standard deviation in the measured density is proportional to <TEX>$A^{-0.46}$</TEX>, where A is the area of scan aperture. The accuracy of position repeatability is <TEX>${\pm}1{\mu}m$</TEX>, and that of density repeatability is <TEX>${\pm}(0.003{\sim}0.03)D$</TEX>. Callier coefficient is determined to be 1.37; the semispecular density is directly proportional to the diffuse density up to 3.5D. Because the logarithmic amplifier has a finite response time, the densities measured at high scan speeds are underestimated to the degree that speeds higher than 200 csu are inadequate for making an accurate astronomical photometry. After power is on, an about 5 hour period of warming is required to stabilize the system electrically and mechanically as well. On the basis of this performance test, we have determined the followings as the optimum scan parameters for the astronomical photometry: For the scan aperture <TEX>$10\;\sim\;20{\mu}m$</TEX> is optimal, and for the scan speed. <TEX>$20\;{\sim}\;50$</TEX> csu is appropriate. These parameter values are chosen in such a way that they may keep the density repeatability within <TEX>${\pm}0.01D$</TEX>, the position displacement under <TEX>$1{\mu}m$</TEX>, and the density underestimation below 0.1D even in high density regions.
1043
- Lee, Hyung-Mok
- 天文學會誌 = The journal of the Korean Astronomical Society
- 25, n.2
- pp.111-128
- 1992
- 원문 바로보기
Infrared emissions from spherical dust, clouds are calculated using quasi-diffusion method. We have employed graphite-silicate mixture with power-law size distribution for the dust model. The grains are assumed to be heated and cooled by radiative processes only. The primary heating source is diffuse interstellar radiation field. hut the cases with an embedded source are also considered. Since graphite grains have higher temperature than silicate grains, the observed IR emission is mainly due to graphite grains, unless the fraction of graphite grains is negligibly small. The color temperature of Bok globules obtained from IRAS 60 and <TEX>$100{\mu}m$</TEX> data are found to be consistent with the dust cloud with graphite-silicate mixture exposed to average interstellar radiation field. The color temperature is sensitive to the external radiation field, but rather insensitive to the size distribution of the grains. We found that the density distribution can be recovered outside the beam size using the inversion technique that assumes negligible optical depth. However, the information within the beam size is lost for if beam convolved intensity distributions are used in deriving density profile.
1044
BLUE STRAGGLERS, CATACLYSMIC VARIABLES, X-RAY BINARIES, AND MILLISECOND PULSARS IN GLOBULAR CLUSTERS
- Lee, Hyung-Mok
- 天文學會誌 = The journal of the Korean Astronomical Society
- 25, n.1
- pp.47-64
- 1992
- 원문 바로보기
Cores of globular clusters are an ideal place for close encounters between stars. The outcome of tidal capture can be stellar mergers, close binaries between normal stars (W UMa type), cataclysmic variables composed of white dwarf and normal star pairs, or low-mass X-ray binaries consisting of a neutron star and a normal star pairs. Stellar mergers can be the origin of blue stragglers in dense globular clusters although they are hard to observe. Low mass X-ray binaries would eventually become binary pulsars with short pulse periods after the neutron stars accrete sufficient amount of matter from the companion. However, large number of recently discovered, isolated millisecond pulsars (as opposed to binary pulsars) in globular clusters may imply that they do not have to gain angular speeds during the X-ray binary phase. We propose that these isolated millisecond pulsars may have formed through the disruptive encounters, which lead to the formation of accretion disk without Roche lobe filling companion, between a neutron star and a main-sequence star. Based on recently developed multicomponent models for the dynamical evolution of globular clusters, we compute the expected numbers of various systems formed by tidal capture as a function of time.
1045
- Rhee, Myung-Hyun
- 天文學會誌 = The journal of the Korean Astronomical Society
- 25, n.1
- pp.11-21
- 1992
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Applying mass model to disk galaxy NGC 300, since the observed rotation curve of NGC 300 is flatter than Toomre's mass model n = 1, two cases are used; obtaining parameters <TEX>$a^n$</TEX> and <TEX>$b^n$</TEX> from the polynomial fitting of the observed rotation curve (case A) and from the least square fitting between the observed rotation curve and model rotation curve (case B). In any case, n bas a fixed value of 1. Brandt's mass model is also discussed. which has a shape parameter n = 1.4. Calculated total mass and total mass to luminosity ratio are <TEX>$3.3{\times}10^{10}M_{\odot}$</TEX>, l2.1 for case A and <TEX>$2.8{\times}10^{10}M_{\odot}$</TEX>, 10.3 for case B. In case of Brandt's model, the values are <TEX>$4.2{\times}10^{10}M_{\odot}$</TEX> and 15.4. The rise in the local mass to luminosity ratio in the outer part of NGC 300 implies existence of massive halo. Other dynamical properties are also discussed.
1046
- La, Daile
- 天文學會誌 = The journal of the Korean Astronomical Society
- 25, n.2
- pp.105-109
- 1992
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We show that spacing patterns of planets and satellites in the solar system are formulatable in a single form. It is suggested that a possible explanation for the rule might be the orbital resonance effect, which has existed at an earlier epoch of the solar (planet) system. By extrapolating the formulated spacing patterns beyond the sun-Pluto distance, we find the sun-Planet X distance falls in a range (<TEX>$46{\sim}79$</TEX>) A. U..
1047
- Chang, Kyong-Ae
- 天文學會誌 = The journal of the Korean Astronomical Society
- 25, n.2
- pp.79-90
- 1992
- 원문 바로보기
The physical properties of the flux factor K and its application are discussed in connection to the high amplification events. The effects due to random motions of stars in a foreground galaxy are examined in the frame work of moving caustics of gravitational microlenses.
1048
- Sung, Hwan-Kyung
- 天文學會誌 = The journal of the Korean Astronomical Society
- 25, n.2
- pp.91-104
- 1992
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New photoelectric UBV Photometry of 112 stars in open cluster M35 field was obtained. The distance modulus and age of the cluster are <TEX>$9.^m3$</TEX>(725pc) and <TEX>$8.5{\times}10^7yrs$</TEX>, respectively. The internal differential reddening within the cluster is apparent.
1049
- Oh, K.S.
- 天文學會誌 = The journal of the Korean Astronomical Society
- 25, n.1
- pp.1-9
- 1992
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We present new approach to analysis of velocity data of globular clusters. Maximum likelihood method is applied to get model parameters such as central potential, anisotropy radius, and total mass fractions in each mass class. This method can avoid problems in conventional binning method of chi-square. We utilize three velocity components, one from line of sight radial velocity and two from proper motion data. In our simplified scheme we adopt 3 mass-component model with unseen high mass stars, intermediate visible stars, and low mass dark remnants. Likelihood values are obtained for 124 stars in M13 for various model parameters. Our preferred model shows central potential of <TEX>$W_o=7$</TEX> and anisotropy radius with 7 core radius. And it suggests non-negligible amount of unseen high mass stars and considerable amount of dark remnants in M13.
1050
- Park, Y.S.
- 天文學會誌 = The journal of the Korean Astronomical Society
- 25, n.2
- pp.67-78
- 1992
- 원문 바로보기
Effects of cloud rotation 011 the profiles of CO J=<TEX>$1{\rightarrow}0$</TEX> lines arc investigated by theoretically general ing line profiles under physical conditions similar to t he ones in large globules. The synthesized profiles are presented and their characteristics are discussed. It is found that when the Doppler shift of the observed CO lines is interpreted as the rotation velocity, the optically thin <TEX>$^{13}CO$</TEX> lines underestimate the rotation velocity by up to 10 percents, while the self-reversed optically thick <TEX>$^{12}CO$</TEX> lines overestimate the velocity up to 20 percents. The optically thin line is shown to be of use in probing the distribution of rotation velocity in dark globules.