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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 108/119
1071
- 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>.
1072
- 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.
1073
- Yun, Hong-Sik
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.1
- pp.79-95
- 1988
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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).
1074
- 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>.
1075
- 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.
1076
- Lee, Jeong-Woo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 20, n.1
- pp.27-47
- 1987
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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.
1077
- Ann, Hong-Sik
- 天文學會誌 = The journal of the Korean Astronomical Society
- 20, n.2
- pp.49-62
- 1987
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Using the detailed two-dimensional surface photometry of 39 galaxies, the observed profiles are decomposed into spheroid, disk and bar components simultaneously. From the analyses of decomposition parameters, the correlations among the three components are investigated to find the global property of barred galaxies. And the lens and ring components, and spiral arm patterns are also examined with Hubble type and decomposition parameters.
1078
- Lee, Jeong-Woo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 20, n.2
- pp.95-95
- 1987
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1079
- Shin, Jun-Ho
- 天文學會誌 = The journal of the Korean Astronomical Society
- 20, n.1
- pp.1-26
- 1987
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By inverting the brightness integral for the dust-scattered continuum, we have determined how the dust grains are distributed inside the Orion nebula. The scattering characteristics of the Orion dust at a given wavelength is kept constant within the nebula, and the geometry of the nebula is assumed to have a hemispherical shape. The resulting radial distance dependence of the distribution of dust number density, <TEX>$N_d(r)$</TEX>, shows that the dust grains are depleted at the central region of the Orion nebula and concentrated in the region <TEX>$5'{\sim}6'$</TEX> away from the Trapezium stars. The scattering characteristics of the Orion dust are of moderately forward throwing nature, and the Orion dust has low values of albedo.
1080
- Ann, Hong-Bae
- 天文學會誌 = The journal of the Korean Astronomical Society
- 19, n.2
- pp.69-89
- 1986
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The global morphology and geometric parameters of 39 barred galaxies are investigated, by using isophote map and isodensity tracings obtained from detailed surface photometry with the Kiso V-band plates. The observed results are as follows: i) There is no strong indication that the ratio of bar length to disk size is correlated with Hubble type, except that the largest bars appear in the SBb galaxies. ii) The mean value of axial ratios of bars is <TEX>$2.0{\pm}0.4$</TEX> and there is a trend that early type galaxies have smaller axial ratios than late type galaxies. iii) About 15% of early type barred galaxies(Sb0-SBb) have triaxial bulges.