모달창 닫기
- 홈으로 이동
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, 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>.
1082
- Whang, Yun-Oh
- 天文學會誌 = The journal of the Korean Astronomical Society
- 22, n.1
- pp.1-24
- 1989
- 원문 바로보기
By applying population synthesis method, stellar populations in the nuclei of M31 and M32 are studied. We obtained five and four models for M31 and M32 respectively, for different main sequence turn-offs and keeping the astrophysical constraints as loose as possible. The best models for M31 and M32 are thought to have G0-5 and F5-8 main sequence trun-offs respectively. These models show that the main sequence stars outnumber the giants, which indicates the dwarf-dominance in external galactic nuclei. Even though there are some computational difficulties because of non-uniqueness in solution, two major points can be pointed out when compared to the previous papers. First, the ultraviolet deficiency expected from the conventional metal rich population models is not detected in our models, Instead ultraviolet radiation turns out to be somewhat higher than that of observation. Second one is the minor contribution from the Super Metal Rich (SMR) K giants to the integrated light of the program galaxies. That is, in our models, the SMR contribution is at best the same level as normal giants contrary to the SMR dominance of previous models. Since the loose astrophysical constraints are the major difference of our study from the previous ones, one should re-examine carefully for their validity further.
1083
- 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).
1084
- 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.
1085
- 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.
1086
- Hong, S.S.
- 天文學會誌 = The journal of the Korean Astronomical Society
- 22, n.1
- pp.63-79
- 1989
- 원문 바로보기
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.
1087
- 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.
1088
- 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.
1089
- 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.
1090
- Chun, Mun-Suk
- 天文學會誌 = The journal of the Korean Astronomical Society
- 21, n.1
- pp.67-77
- 1988
- 원문 바로보기
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.