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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 109/122
1081
- Lee, See-Woo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 22, n.1
- pp.43-61
- 1989
- 원문 바로보기
The ages of field stars given in the catalogue of Cayrel de Strobel et al. (1985) are derived by the five different methods with combination of theoretical isochrones. By using these ages and metal abundances homogenized by Lee and Choe (1988), the age-metallicity relations are obtained. For disk stars of [Fe/H] > -0.9, the present age-metallicity relations are nearly consistent with those given by Twarog (1980) and Carlberg et al. (1985).
1082
- Kwon, Suk-Min
- 天文學會誌 = The journal of the Korean Astronomical Society
- 22, n.2
- pp.141-160
- 1989
- 원문 바로보기
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.
1083
- Lee, Yoo-Mi
- 天文學會誌 = The journal of the Korean Astronomical Society
- 22, n.1
- pp.31-41
- 1989
- 원문 바로보기
Luminosity profile of the late type spiral galaxy NGC 2403 was obtained using the PDS scan of the plate. Some physical parameters (scale length, total magnitude, central brightness, disk to bulge ratio and concentric indices) were calculated from the brightness distribution. Total mass and the mass to luminosity ratio were estimated from the fitting of various mass models.
1084
- Hong, S.S.
- 天文學會誌 = The journal of the Korean Astronomical Society
- 22, n.2
- pp.127-140
- 1989
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Problem of the diffuse radiation (DFR) transfer is solved exactly for pure hydrogen nebulae of uniform density, and accuracies of the on-the-spot (OTS) approximation are critically examined. For different values of density and spectral types of the central star, we have calculated the degree of ionization and the kinetic temperature of electrons as functions of distance from the central star, and compared them with the corresponding results of the OTS approximation. At most locations inside an HII region. the DFR ionizes considerable amount of hydrogen; therefore, the OTS approximation under-estimates the size of ionized regions. The exact treatment of the DFR transfer results in an about 10 to 20 percent increase in the classical <TEX>$Str{\ddot{o}}mgren$</TEX> radius. The OTS approximation overestimates the local heating rate by raising the density of neutral hydogens. Consequently, it predicts higher values for the local electron temperature. The OTS approximation also exaggerates the dependence of electron temperature on density. When the hydrogen density is changed from <TEX>$10/cm^3$</TEX> to <TEX>$10^3/cm^3$</TEX> with an 06.5V star, the OTS approximation shows an about 3,000 K difference in the electron temperature, while the exact treatment of the DFR-transfer reduces the difference to about 1,000 K. The OTS approximation fails to demonstrate the brightening of the electron temperature close to the ionization boundary.
1085
- Lee, Sang-Gak
- 天文學會誌 = The journal of the Korean Astronomical Society
- 22, n.2
- pp.101-111
- 1989
- 원문 바로보기
We have analysed the proper motion data of LHS catalog, to derive the faint end of the luminosity function more precise than ever before, by mean absolute method, and by making use of the reudced proper motion diagram. It is found that the relations between the mean absolute magnitude and the reduced proper motion for main sequence stars, subdwarfs, and white dwarfs are so different that the proper application of an appropriate relation to each group is much more important. The derived luminosity function shows the broad maximum peak from <TEX>$M_B{\sim}14$</TEX> to <TEX>$M_B{\sim}17$</TEX> and declines after <TEX>$M_B{\sim}17$</TEX> up to <TEX>$M_B{\sim}22$</TEX>.
1086
- Kim, K.T.
- 天文學會誌 = The journal of the Korean Astronomical Society
- 22, n.1
- pp.25-30
- 1989
- 원문 바로보기
We report a null detection of <TEX>$^{12}CO$</TEX> emission from a sub-condensation in a High Velocity Cloud (HVC). As a consequence of this, an upper limit of <TEX>$n(H_2)\frac{X(CO)}{DV/DR}{\leq}2{\times}10^{-5}$</TEX> was set. This implies that <TEX>$^{12}CO$</TEX> abundance is deficient by at least a factor of 10 if the HVC is predominantly molecular, otherwise the CO abundance of the HVC might be normal.
1087
- Chang, Kyong-Ae
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.2
- pp.97-104
- 1988
- 원문 바로보기
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.
1088
- Woo, Jong-Ok
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.1
- pp.57-65
- 1988
- 원문 바로보기
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.
1089
- Chae, Jong-Chul
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.2
- pp.105-116
- 1988
- 원문 바로보기
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.
1090
- 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).