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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 117/122
1161
- 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.
1162
- 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>$0
1163
- Yun, Hae-Young
- 天文學會誌 = The journal of the Korean Astronomical Society
- 12, n.1
- pp.17-25
- 1979
- 원문 바로보기
The two methods for the derivation of helium abundance are presented. The magnitude of the largest bump along the red giant branch is fainter as helium abundance decreases and metal abundance increases. Using this relation and observed bump magnitude, the He-abundances of globular clusters are estimated. The another method is to use the relation that the ratio of asymptotic giant branch and horizontal branch stars increases with decreasing He-abundance. The comparison of the He-abundances derived from the two methods with those derived from the other two methods shows that they are consistent within the dispersion less than <TEX>${\Delta}Y=0.1$</TEX>.
1164
- Kim, Yong-Duk
- 天文學會誌 = The journal of the Korean Astronomical Society
- 12, n.1
- pp.7-9
- 1979
- 원문 바로보기
The rate of gravitational quadrupole radiation is derived in the formalism of source theory. It is also shown that gravitational superradiance is theoretically possible.
1165
- Hong, Seung-Soo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 12, n.1
- pp.27-34
- 1979
- 원문 바로보기
Temperature history of very small interstellar dust particles is followed under diffuse interstellar radiation. Because of extremely small thermal capacities of these grains with sizes ranging from a few tens to hundred Angstroms in radii, they are to experience strong fluctuations in temperature whenever they are hit by interstellar ultraviolet photons. Fluctuating temperature can inhibit these smaller component of interstellar dust from growing into core-mantle particles of submicron sizes by continuously evaporating atoms and molecules adsorbed on their surface. This is interpreted as a possible physical reason for the bimodal nature in grain size distribution. A brief discussion is also given to the far infrared emission properties of such small grains in diffuse interstellar dust clouds.
1166
- Lee, See-Woo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 11, n.1
- pp.1-30
- 1978
- 원문 바로보기
The four dimensional classification of globular dusters with the parameters, Z, Y, age and HB type is presented defining two new parameters. <TEX>$(B-V)_{1/2}\;and\;S_{3/2}$</TEX> which are shown to be tightly correlated with Kinman's spectral types and the helium abundances obtained from the R-method, respectively. The Z- and Y- abundances are derived from <TEX>$(B-V)_{1/2}\;and\;S_{3/2}$</TEX>, respectively, and the latter parameters determine the age class of clusters with help of Dickens' HB type, which is a function of Z. Y and age. For the examined forty two globular clusters the computed range at Z and Y are <TEX>$1.5{\times}10^{-4}{\leq}Z{\leq}4.5{\times}10^{-2}\;and\;0.23</TEX><TEX><</TEX><TEX>Y{\leq}0.41$</TEX>. The age difference between the oldest (HB type 1) and the youngest (HB type 7) clusters is roughly estimated to be <TEX>$2-4{\times}10^9$</TEX> years. Using these four parameters the known anomalous C-M diagrams seem to be reasonably interpreted without taking into account some complicate parameters such as unusually overabundant heavy elements, mass loss and mass spread, etc. The four dimensional scheme strongly suggests the slow successive collapses of the proto-Galaxy rather than a single fast collapse, and by this slow collapse model the inversion of chemical abundance gradient in the Galaxy can be explained. It is also shown that the clump position along the RGB near the HB level removes down to the fainter magnitude as the Z(Y)- abundance increases (decreases).
1167
- Yun, Hong-Sik
- 天文學會誌 = The journal of the Korean Astronomical Society
- 11, n.1
- pp.37-46
- 1978
- 원문 바로보기
A hydrostatic model atmosphere of a typical umbral core is constructed on the basis of both Na I <TEX>$D_2$</TEX> line profile and umbral core-to disk continuum intensity ratio. The observations were obtained by Mullan and Wyller with photoelectric means over the range from <TEX>$4000{\AA}\;and\;6500{\AA}$</TEX>. The computed line profile of Na I <TEX>$D_2$</TEX> and the emergent continuum intensity distribution are compared with the observations. The temperature of umbral cores is found to be lower by <TEX>$300^{\circ}K\;to\;500^{\circ}K$</TEX> than that of their ambient umbral region. The detailed physical structure of a working model of umbral cores is proposed.
1168
- 이은성
- 天文學會誌 = The journal of the Korean Astronomical Society
- 11, n.1
- pp.47-54
- 1978
- 원문 바로보기
Twelve Chih was sasigned to each day in the old Chinese calendar. This paper clarifres the relations between 12 Chih and the diurnal motion of Big Dipper or the clock, and it shows the long term table and formula for the dayly assignment of 12 Chih in the calendar.
1169
- Beebe, Reta Fay
- 天文學會誌 = The journal of the Korean Astronomical Society
- 11, n.1
- pp.55-58
- 1978
- 원문 바로보기
An extensive molecular equilibrium calculation has been performed under sunspot conditions in order to resolve the current dispute on the presence of <TEX>$C_2$</TEX> lines in the spectrum of sunspots. Equilibrium abundance of <TEX>$C_2$</TEX> has been computed under the conditions of umbral cores, umbrae and the normal photosphere. As the results, it is found that the umbral cores yield unfavorable environment for <TEX>$C_2$</TEX> formation. It is concluded that <TEX>$C_2$</TEX> molecular lines are not likely tn be observed in the spectrum of sunspots.
1170
- Hong, Seung-Soo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 11, n.1
- pp.31-36
- 1978
- 원문 바로보기
Although Serkowski used a single value K=1.15 in representing all the observed interstellar linear polarization curves by his empirical relation <TEX>$p({\lambda})/P_{max}$</TEX>=exp (-K <TEX>$1n^2({\lambda}_{max}/{\lambda})$</TEX>), where <TEX>$p_{max}$</TEX> is the maximum polarization at wavelength <TEX>${\lambda}_{max}$</TEX>, we have noticed a meaningful variation in K from observations of 72 stars. By comparing K's with <TEX>$P_{max}/E_{B-V}\;and\;with\;{\lambda}_{max}$</TEX>, we have examined how the shape of the polarization curve is related with the degree of grain alignment on one hand, and with grain sizes on the other. We have shown that correlations between K, <TEX>$P_{max}/E_{B-V}\;and\;with\;{\lambda}_{max}$</TEX>, are consistent with the idea of Davis-Greenstein mechanism for grain alignment.