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1968년 ~ 2025년까지 1,227 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 : 1,227건 (DB Construction : 1,227 Articles)
총 게시글 1,227건
페이지 111/123
1101
- 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>.
1102
- 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.
1103
- 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.
1104
- 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.
1105
- 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.
1106
- 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).
1107
- Lee, See-Woo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.2
- pp.182-182
- 1988
- 원문 바로보기
1108
- 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.
1109
- 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.
1110
- Lee, Sang-Gak
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.2
- pp.173-181
- 1988
- 원문 바로보기
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.