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- 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 107/119
1061
- Kwon, Suk-Min
- 天文學會誌 = The journal of the Korean Astronomical Society
- 22, n.2
- pp.141-160
- 1989
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In order to derive time dependence of the atmospheric diffuse light, which consists of the airglow continuum emission and diffusely scattered radiations of the intergrated starlight, the diffuse Galactic light, and the zodiacal light, we have analyzed the meridian scan observations of the sky brightness at <TEX>$5,080\;{\AA}$</TEX> and <TEX>$5,300\;{\AA}$</TEX>. Amplitude of the time-variation becomes larger for lower elevation, and maximum amplitude is found to be about <TEX>$50\;S_{10}(V)_{G2V}$</TEX> at elevation <TEX>$10^{\circ}$</TEX>. The atmospheric diffuse radiation attains maximum brightness at around midnight, and afterward it decreases slowly with time. The time-variations for the two wavelengths are similar to each other. The observed brightness distribution of the diffuse light along the zenith distance is fitted to an empirical relation of two parameters. By making the two parameters time-dependent, we describe the spatial and time variations of the atmospheric diffuse light. This enables us to make time dependent correction for the atmospheric diffuse component in the reduction of zodiacal light brightness.
1062
- Hong, S.S.
- 天文學會誌 = The journal of the Korean Astronomical Society
- 22, n.1
- pp.63-79
- 1989
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Current estimates, based on the same star-count analysis, of the distance to the globule Bamard 361 range from 300 pc to 650 pc. All the problems associated with the estimates have been fully rectified in this study, and a modification has been made to the classical Wolf diagram to improve the accuracy in the distance determination. A reference field was carefully selected close to the globule but well outside the globule boundary, and star counts for this field were performed on the blue POSS plate in order to set up the reference magnitude sequence appropriate to the general area of B 361. From the reference sequence, the stellar density function has been derived specifically for the direction toward the globule. Correction was made for the general interstellar extinction, and the luminosity function with the Wielen's dip was adopted. The resulting density function clearly reveals the existence of the local Cygnus-Orion arm in the direction of B 361 at about 700 pc away from the Sun. Analysis of the star-count data for the program field locates the globule at distance <TEX>$600{\pm}50$</TEX> pc ; thus, the globule is an object located in the Cygnus-Orion arm, residing somewhat toward its leading edge.
1063
- Woo, Jong-Ok
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.1
- pp.57-65
- 1988
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The absolute measurements of fluxes in the region <TEX>${\lambda}{\lambda}3,100-8,090\;{\AA}$</TEX> emitted in the visible continua of some galactic Wolf-Rayet stars are presented. These observations were made by a two-channel scanner which was built up cooperatively by the Observatoire of Lyon and the Laboratoire d'Astronomie Spatiale. The fluxes, dereddened from those data, were combined with IUE and ANS ultraviolet measurements. These fluxes were compared with those of LTE plane paralleled model atmospheres of Kurucz (1979) and were also integrated in order to derive effective temperatures and bolometric corrections for the program stars. The derived effective temperatures and bolometric corrections for the stars were in the range of <TEX>$25,000\;K{\sim}32,700\;K$</TEX>, and of <TEX>$-2.5\;mag.{\sim}-3.7\;mag.$</TEX>, respectively.
1064
- Chae, Jong-Chul
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.2
- pp.105-116
- 1988
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We have investigated hydrodynamical behaviors of spicules by solving numerically the hydrodynamic equations subject to proper boundary conditions using the method of characteristics. We examined the behaviors of MHD slow mode waves propagating through rigid magnetic flux tubes which were excited by the pressure perturbations at the lower boundary. It is found that the spicules are identified as the manifestation of the movement of the transition region being pushed upward by collisions with the shock waves. One of the most important findings is the presence of the rebound shocks and their roles. We interpreted the rebound shocks in terms of the observed recurrent spicules.
1065
- Lee, Sang-Gak
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.2
- pp.173-181
- 1988
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The usual method of classification for metal poor stars is based on the normal standard stars. In this study, we show that among the sample of stars classified by this method, a systematic bias in the observed classes of metal weakness is found and, also that this method is not appropriate for classification of metal poor stars, by showing that the spectral line dependences on the temperature and pressure in the extreme metal poor stars are different from those in the normal standard stars. Therefore, we suggest that the 3-dimensional classification system, like 2-dimensional MK system, is necessary for an accurate classification of metal poor stars.
1066
- Chun, Mun-Suk
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.1
- pp.67-77
- 1988
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Nine giant star's spectra in NGC 3201 were obtained using the image tube in Sutherland. From the analysis of these spectra we found the increase of Ca I and CH abundances with decreasing the radial distnace, but CN, Ca II and Fe abundances do not show this. Dependence of the calculated parameters seems to exist among CN, Ca I, Ca II and CH abundances.
1067
- Hong, Seung-Soo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.2
- pp.155-171
- 1988
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We have examined how sensitively the extinction value determined by the method of star-count depends on such factors as the plate limit, the size of counting reseau, the non-linearity in the number distribution of stars with magnitude, and the angular resolution demanded by the given problem. We let the Poisson distribution portray the statistical nature of the countings, and chose the region containing the globule Barnard 361 as an example field. Uncertainties due to various combinations of the factors are presented in graphic forms: (1) Dynamic range in the extinction measurements is evaluated as a function of reseau size for varying plate limits. (2) Statistical errors involved in the star-count are analized in terms of the signal-to-noise ratio, the plate limit and the reseau size. (3) Systematic error due to the non-linearity in the number distribution are thoroughly analized. (4) Finally, a methodology is presented for correcting the systematic error in the observed radial density gradient. These graphs are meant to be used in selecting proper size of the reseau and in estimating errors inherent to the star-count analysis.
1068
- Lee, See-Woo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.2
- pp.182-182
- 1988
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1069
- Lee, See-Woo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.1
- pp.37-55
- 1988
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Combining the luminosity functions of main sequence stars in 3 associations and 22 open clusters, the initial luminosity function and mass function for these clusters are derived. For stars of m > <TEX>$0.6m_{\odot}$</TEX>, they are well consistent with those for the field stars.
1070
- Lee, See-Woo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.1
- pp.1-36
- 1988
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The temperature calibration of stars by photometric parameters and spectral type is discussed, using the catalogue data of Cayrel de Strobel et al. (1985) and Morel et al. (1976). The H-R diagrams and the mass-luminosity relation of stars in this catalogue are presented in the [log(L/M)-log <TEX>$T_e$</TEX>]-and [<TEX>$M_{bol}$</TEX>-log(L/M)]-planes, respectively, discussing the age of main sequence (MS) stars and giant stars. The age-metallicity relation of the nearby stars suggests the initial rapid enrichment of metal abundance.