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 116/122
1151
- 우종옥
- 天文學會誌 = The journal of the Korean Astronomical Society
- 14, n.1
- pp.43-49
- 1981
- 원문 바로보기
Making use of log <TEX>$T_{eff}-M_{bol}$</TEX> diagram along with Stohers' stellar evolutionary tracks (1972), we estimated the masses of 107 O stars in HII regions, which were selected from the catalogue compiled by Goy (1973). It is found that our estimated masses of O stars range from <TEX>$20M_{\odot}\;to\;120M_{\odot}$</TEX> and about 20% of them falls in the mass range above <TEX>$60M_{\odot}$</TEX> in agreement with earlier findings of Conti et al. (1975).
1152
- Lee, H.M.
- 天文學會誌 = The journal of the Korean Astronomical Society
- 14, n.2
- pp.79-87
- 1981
- 원문 바로보기
Theoretical profiles of selected rotational lines of <TEX>$C_2$</TEX> CH, CN, TiO and MgH are computed by using the current models of sunspot unbrae and penumbrae. It is found that the lines of the diatomic carbides are enhanced in penumbrae relative to umbrae, while MgH lines are more strongly enhanced in umbrae than in penumbrae and the quiet photosphere. The results are discussed with respect to selecting lines suitable for studying the structure of sunspots.
1153
- Hong, Seung-Soo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 13, n.1
- pp.35-44
- 1980
- 원문 바로보기
Various assumptions used in interpreting the observations of hydrogen recombination lines are critically assessed to confirm the gradient of electron temperature with distance from the galactic center. The total temperature increase from 5 to 13 kpc is about 2,500 K. Among many suggestions, we have singled out the decrease of trace dement abundances with the galactoccntric distance as the most viable cause for the temperature gradient. This will impose an important constraint on evolutionary models of the Galaxy.
1154
- Minn, Y.K.
- 天文學會誌 = The journal of the Korean Astronomical Society
- 13, n.1
- pp.9-14
- 1980
- 원문 바로보기
The abundances of simple molecules are examined in terms of the time-dependent cloud evolution. The formation and destruction mechanisms of <TEX>$H_2CO$</TEX> are reviewed. The average value of the fractional abundance of <TEX>$H_2CO$</TEX> is derived to be in the range of <TEX>$10^{-10}\;to\;5{\times}10^{-9}$</TEX>. This is comparable to the observed values. The expected variations of the molecules formed from or destroyed by CO, CI, and <TEX>$C^+$</TEX> whose abundances depend on the evolutionary state of the cloud are discussed.
1155
- Chun, M.S.
- 天文學會誌 = The journal of the Korean Astronomical Society
- 13, n.1
- pp.27-33
- 1980
- 원문 바로보기
Surface density distributions for globular clusters were obtained from photoelectric surface photometry (using centered aperture photometry). These surface brightness profiles were then compared with the theoretical surface density distribution of King's model. From the comparison of the theoretical and observed surface density distributions, we determine he structural parameters of the clusters (the core radius <TEX>$r_c$</TEX>, the tidal cut off <TEX>$r_t$</TEX>, and the concentration factor C).
1156
- Lee, See-Woo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 13, n.1
- pp.45-62
- 1980
- 원문 바로보기
Defining a metal parameter <TEX>$(Sp)_c$</TEX>, which is related to the morphological parameters of C-M diagrams, we have estimated metal abundances for 97 globular clusters in our Galaxy. A correlation between absolute magnitude of the horizontal branch and metal abundance is derived, which is used for the determining distances to globular clusters whose visual magnitudes of the horizontal branch are known. The space distribution of globular clusters and the chemical evolution of the halo are examined. Our analysis suggests an initial mean gradient of metallicity to be d[Fe/H]/<TEX>$dr_G$</TEX> = -0.06 <TEX>$kpc^{-1}$</TEX> for the halo in galactocentric distance, <TEX>$r_G$</TEX><20 kpc. Our findings also imply a slow collapse of protogalaxy.
1157
- Yun, Hong-Sik
- 天文學會誌 = The journal of the Korean Astronomical Society
- 13, n.1
- pp.1-8
- 1980
- 원문 바로보기
Simultaneous observations of high resolution spectra of CaII H, K, <TEX>${\lambda}8542\;and\;{\lambda}8498$</TEX> have been made over a sunspot umbra (SPO 5007) by means of Sacramento Peak Observatory's HIRKHAD program with the Echelle spectrograph at the Vacuum Tower Telescope. The observed spectra scanned by SPO's fast microphotometer have been reduced for later theoretical interpretations. The reduced profiles, sampled over a region which is thought to be coolest over the spot, are presented in units of absolute intensity. The core intensity ratios of <TEX>$I(K_3)/I(H_3);and\;I({\lambda}8498)/I({\lambda}8542)$</TEX> arc found to be 1.3 and 1.14, respectively.
1158
- Lee, See-Woo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 13, n.1
- pp.15-26
- 1980
- 원문 바로보기
The BV-photographic photometry was made for 1714 stars (V<19.5) in NGC 6752. The C-M diagram of this cluster shows an unusually extended blue horizontal branch <TEX>$(V=13.5{\sim}17.8)$</TEX> with a wide gap <TEX>$(V=16{\sim}16.7)$</TEX> and the well defined giant branch with gaps at V=13.85 and 16.2. The turnoff point is defined at <TEX>$V=17.25{\pm}0.15$</TEX> and (B-V) = <TEX>$0.46{\pm}0.02$</TEX>. If we take <TEX>$V_{HB}=13.85$</TEX> for NGC 6752, then <TEX>${\Delta}V=2.80,\;(B-V)_{0,g}=0.76\;and\;{\Delta}V_{TO}=3.40$</TEX> and the chemical abundance is estimated to be [Fe/H]=-1.67 or <TEX>$Z=4.3{\times}10^{-4}\;and\;Y=0.26$</TEX>. Some other physical parameters of this cluster are derived and compared with those for the well observed clusters M 3, M 13, M 15 and M 92.
1159
- 현정준
- 天文學會誌 = The journal of the Korean Astronomical Society
- 12, n.1
- pp.1-5
- 1979
- 원문 바로보기
The usual assumption of the pressure equilibrium between the convective elements and the surrounding fluid has been dropped, and the effects of the pressure perturbation of the convective element on its velocity and T perturbation have been estimated.
1160
- Lee, See-Woo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 12, n.1
- pp.41-70
- 1979
- 원문 바로보기
From <TEX>$B\ddot{o}hm$</TEX>-Vitense's atmospheric model calculations, the relations, [<TEX>$T_e$</TEX>, (B-V)] and [B.C, (B-V)] with respect to heavy element abundance were obtained. Using these relations and evolutionary model calculations of Rood, and Sweigart and Gross, analytic expressions for some physical parameters relating to the C-M diagrams of globular clusters were derived, and they were applied to 21 globular clusters with observed transition periods of RR Lyrae variables. More than 20 different parameters were examined for each globular cluster. The derived ranges of some basic parameters are as follows; <TEX>$Y=0.21{\sim}0.33,\;Z=1.5{\times}10^{-4}{\sim}4.5{\times}10^{-3},\;age,\;t=9.5{\sim}19{\times}10^9$</TEX> years, mass for red giants, <TEX>$m_{RG}=0.74m_{\odot}{\sim}0.91m_{\odot}$</TEX>, mass for RR Lyrae stars, <TEX>$m_{RR}=0.59m_{\odot}{\sim}0.75m_{\odot}$</TEX>, the visual magnitude difference between the turnoff point and the horizontal branch (HB), <TEX>${\Delta}V_{to}=3.1{\sim}3.4(</TEX><TEX><</TEX><TEX>{\Delta}V_{to}</TEX><TEX>></TEX><TEX>=3.32)$</TEX>, the color of the blue edge of RR Lyrae gap, <TEX>$(B-V)_{BE}=0.17{\sim}0.21=(</TEX><TEX><</TEX><TEX>(B-V)_{BE}</TEX><TEX>></TEX><TEX>=0.18),\;[\frac{m}{L}]_{RR}=-1.7{\sim}-1.9$</TEX>, mass difference of <TEX>$m_{RR}$</TEX> relative to <TEX>$m_{RG},(m_{RG}-m_{RR})/m_{RG}=0.0{\sim}0.39$</TEX>. It was found that the ranges of derived parameters agree reasonably well with the observed ones and those estimated by others. Some important results obtained herein can be summarized as follows; (i) There are considerable variations in the initial helium abundance and in age of globular clusters. (ii) The radial gradient of heavy element abundance does exist for globular clusters as shown by Janes for field stars and open clusters. (iii) The helium abundance seems to have been increased with age by massive star evolution after a considerable amount (Y>0.2) of helium had been attained by the Big-Bang nucleosynthesis, but there is not seen a radial gradient of helium abundance. (iv) A considerable amount of heavy elements (<TEX>$Z{\sim}10{-3}$</TEX>) might have been formed in the inner halo (<TEX>$r_{GC}$</TEX><10 kpc) from the earliest galactic co1lapse, and then the heavy element abundance has been slowly enriched towards the galactic center and disk, establishing the radial gradient of heavy element abundance. (v) The final galactic disk formation might have taken much longer by about a half of the galactic age than the halo formation, supporting a slow, inhomogeneous co1lapse model of Larson. (vi) Of the three principal parameters controlling the morphology of C-M diagrams, it was found that the first parameter is heavy clement abundance, the second age and the third helium abundance. (vii) The globular clusters can be divided into three different groups, AI, BI and CII according to Z, Y an d age as well as Dickens' HB types. BI group clusters of HB types 4 and 5 like M 3 and NGC 7006 are the oldest and have the lowest helium abundance of the three groups. And also they appear in the inner halo. On the other hand, the youngest AI clusters have the highest Z and Y, and appear in the innermost halo region and in the disk. (viii) From the result of the clean separations of the clusters into three groups, a three dimensional classification with three parameters, Z, Y and age is prsented. (ix) The anomalous C-M diagrams can be expalined in terms of the three principal parameters. That is, the anomaly of NGC 362 and NGC 7006 is accounted for by the smaller age of the order of <TEX>$1{\sim}2{\times}10^9$</TEX> years rather than by the helium abundance difference, compared with M 3. (x) The difference in two Oosterhoff types I and II can be explained in terms of the mean mass difference of RR Lyrae variables rather than in terms of the helium abundance difference as suggested by Stobie. The mean mass of the variables in Oosterhoff type I clusters is smaller by <TEX>$0