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1968년 ~ 2024년까지 1,211 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 : 1,211건 (DB Construction : 1,211 Articles)
총 게시글 1,211건
페이지 110/122
1091
- Hong, Seung-Soo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.2
- pp.155-171
- 1988
- 원문 바로보기
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.
1092
- Lee, See-Woo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.2
- pp.182-182
- 1988
- 원문 바로보기
1093
- Lee, See-Woo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.1
- pp.37-55
- 1988
- 원문 바로보기
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.
1094
- 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.
1095
- Kim, Kwang-Tae
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.2
- pp.117-132
- 1988
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Multi-frequency polarization observations of Abell 695 are reported here. The brightest radio source 0838+325, which was previously classified as a wide angled head-tail radio source, is, in the present observations, resolved into two separable sources, a head-tail source 0838+325 AB and a diffuse one 0838+325C. The radio-tail shows high degree of linear polarization(<TEX>${\sim}50$</TEX>-25%) along the radio-tail, suggesting that the interaction with its surrounding intracluster medium (ICM) is not highly turbulent. With the present data, thermal particle densities at the locations of these sources are estimated to be n > <TEX>$10^{-5}\;cm^{-3}$</TEX>.
1096
- Chang, Kyong-Ae
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.2
- pp.97-104
- 1988
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This study presents the specific rule governing the image configurations of an extended source for micro lensing of the two body gravitational lens system developed by Chang and Refsdal (1979). Various topological situations of a source are considered in relation to the regions bounded by the so-called critical curves.
1097
- Yun, Hong-Sik
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.1
- pp.79-95
- 1988
- 원문 바로보기
To examine relations between stellar activity and rotation we estimated parameters of stellar activity such as <TEX>$R'_{HK}$</TEX>, <TEX>$R'_{MgII}$</TEX>, <TEX>$R'_{CII}$</TEX>, <TEX>$R'_{CIV}$</TEX> and <TEX>$R'_{X-ray}$</TEX> from the published data which measure the activity levels of stellar chromospheres, transition regions and coronae. In the present study we considered only the main sequence stars in an attempt to minimize the influence of other stellar parameters such as radius, age and stellar convection on stellar activity since they are also known to affect the magnetic field generation. In the present analysis we selected only those stars that satisfy the following conditions: (1) flux measurements are available together with Ca II fluxes and (2) rotation periods are determined by Ca II observations. We derived relations between the <TEX>${\bar{R}}ossby$</TEX> number <TEX>$R_o$</TEX> and stellar activity <TEX>$R'_{HK}$</TEX>, <TEX>$R'_{MgII}$</TEX>, <TEX>$R'_{CII}$</TEX>, <TEX>$R'_{CIV}$</TEX> and <TEX>$R'_{X-ray}$</TEX> and assessed the relations by plotting <TEX>$R'_{HK}$</TEX>, <TEX>$R'_{MgII}$</TEX> and <TEX>$R'_{X-ray}$</TEX> against rotation period <TEX>$P_{rot}$</TEX> for comparison with observations. From the comparison it is found that as far as the rotation-activity relation is concerned, (1) normalized surface flux <TEX>$R'_{HK}$</TEX> is better than the surface flux <TEX>$F'_{HK}$</TEX>, in the sense that <TEX>$R'_{HK}$</TEX> differentiates the color dependence better and (2) <TEX>$R'_{HK}$</TEX> defined by Rutten (1984) describes the observations notably better than <TEX>$R'_{HK}$</TEX> of Noyes et al. (1984).
1098
- Kim, Kwang-Tae
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.2
- pp.133-153
- 1988
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Linear polarization has been measured for fifteen extragalactic radio sources in the field of supernova remnant S 147. These observations were made at 4885, 4835, 1665, 1515, 1465, and 1385 MHz using the Very Large Array, primarily to determine unambiguous Rotation Measures (RM) of the sources. This yields a total of 11 new RM sources. Comparisons of a sample of sources which are seen through S 147 were made with sources located farther away. The result tentatively indicates that the distribution of the rotation measure of the former population is broadened, with more than a 85% level of confidence. This constitutes evidence that there is a SNR contribution to rotation measure in sources seen through the SNR. Limits on this RM contribution are statistically at 30 < | RM | < 70 rad <TEX>$m^{-2}$</TEX> with a 85% statistical level of confidence. These result imply the magnetic field in the rim of S 147 has strength 10 microguass if the electron density is <TEX>$1\;cm^{-3}$</TEX>.
1099
- Sung, Hwan-Kyung
- 天文學會誌 = The journal of the Korean Astronomical Society
- 20, n.2
- pp.63-94
- 1987
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Using many homogeneous data of DDO and UBV colors for all luminosity classes and physical quantities known from spectroscopic observations, new calibration schemes with DDO photometric parameters are presented for metal abundance, effective temperature and surface gravity of stars. And an intrinsic color relation is derived for the reddening estimate.
1100
- Lee, Jeong-Woo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 20, n.1
- pp.27-47
- 1987
- 원문 바로보기
In the present study a two-mode, separately concurring resonant cavity model is proposed for theoretical interpretation of the 3 minute umbral oscillation. The proposed model has been investigated by calculating the transmission coefficients of the waves propagating through the umbral photosphere (photospheric weak-field cavity) and chromosphere (chromospheric strong-field cavity) into the corona, for 3 different umbral model atmospheres by Staude (1982), Beebe et al. (1982) and Avrett (1981). In computing the transmission coefficients we made use of multi-layer approximation by representing the umbra] atmosphere by a number of separate layers with (1) temperature varying linearly with depth and (2) temperature constant within each layer. The medium is assumed to be compressible, non-viscous, perfectly conducting under gravity. The computed resonant periods, transmission spectra, phase spectra, and kinetic energy density of the waves associated with the oscillations are presented in comparison with the observations and their model dependent characteristics are discussed.