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1968년 ~ 2023년까지 1,187 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 : 1,187건 (DB Construction : 1,187 Articles)
총 게시글 1,187건
페이지 111/119
1101
- Chang, K.
- 天文學會誌 = The journal of the Korean Astronomical Society
- 17, n.1
- pp.15-22
- 1984
- 원문 바로보기
The transverse velocities of the gravitational lens system (galaxy plus a 'disturbing star') and their dependences on unkown properties of the source and the deflecting object are discussed. We have derived an analytic expression for the transverse velocity in terms of the velocities of the light source, the gravitational lensing galaxy and the 'disturbing star', and the observer. The results are then further applied to an estimate of the expectation value of the absolute transverse velocity and of the probable time scales of flux changes of the double QSO 0957+561A, B.
1102
- Hong, Seung-Soo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 17, n.2
- pp.115-125
- 1984
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Effect of magnetic field on the thermal instability is studied in the radiatively cooling region behind an interstellar shock of moderate propagation velocity (<TEX>${\sim}10\;km/sec$</TEX>). It is shown that the presence of interstellar magnetic field of a few micro gauss is very effective in preventing the thermal instability from building-up density concentration. In the absence of magnetic field, the shock-induced thermal instability amplifies preshock density inhomogeneity by more than an order of magnitude. However, in the presence of magnetic field, the amplified density contrast is shown to be only a factor 2.
1103
- Woo, Jong-Ok
- 天文學會誌 = The journal of the Korean Astronomical Society
- 17, n.2
- pp.104-114
- 1984
- 원문 바로보기
The effective temperatures, <TEX>$T_{eff}$</TEX> (flux) of 52 early type stars are derived from de-reddened monochromatic and integrated fluxes obtained by absolute spectrophotometry, using the method of graphical analysis pioneered by Blackwell and Shallis (1977), similar to that of Underhill (1982) and Tobin (1983). We also estimated the effective temperatures, <TEX>$T_{eff}$</TEX> (comp) of the same stars by comparing their de-reddened energy distributions with those of the LTE model atmospheres by Kurucz (1979). The effective temperatures derived from these two methods are found to be in good agreement, confirming that they are effective for the estimation of effective temperatures of early type stars.
1104
- Lee, Sang-Gak
- 天文學會誌 = The journal of the Korean Astronomical Society
- 16, n.1
- pp.23-30
- 1983
- 원문 바로보기
About two hundred stars within 50 pc from the sun, whose tangential velocity larger than 100 km/sec, have been selected on the basis of their proper motions and trigonometric parallaxes. A list of them along with their photoelectric UBV data and spectral types is given. The criterion on the tangential velocity, <TEX>$v_t$</TEX> > 132 km/sec, was adopted for selection of high-velocity stars. The H-R diagram of these nearby high-velocity stars resembles that of a globular cluster, with the turnoff around <TEX>$B-V{\approx}0.35$</TEX> and <TEX>$M_v{\approx}4.0$</TEX>, and the subdwarfs among these high-velocity stars are fainter than the main-sequence stars of Hyades by the amount of <TEX>$1^m.25{\pm}0^m.30$</TEX> in the region with B-V < 1.40 on the average.
1105
- Yun, Hong-Sik
- 天文學會誌 = The journal of the Korean Astronomical Society
- 16, n.1
- pp.19-22
- 1983
- 원문 바로보기
The reduced profiles of <TEX>$C_2$</TEX> 5150.56, CN 3864.32, MgH 5150.20 and FeI 5150.84 lines, representing the penumbra, the penumbra-umbra boundary and the umbra of spa 6403 have been analyzed by comparing them with the synthetic profiles computed from a set of umbral and penumbral models. The results are presented and discussed. It is suggested that there may be a significant lateral flow of pbotospheric radiation into the umbral and penumbral regions of the sunspots.
1106
- Kwon, Suk-Minn
- 天文學會誌 = The journal of the Korean Astronomical Society
- 16, n.1
- pp.7-17
- 1983
- 원문 바로보기
During the period between January and November in 1982, UBV photoelectric observations were made for 48 stars in NGC 2264, 66 stars in IC 1805 and 22 stars in IC 348. From these observations, various physical parameters such as distance, mean color excess, total-to-selective extinction ratio and mean age of the clusters were determined. Making use of these parameters, the star formation rates were examined for IC 348 and NGC 2264. The overall formation rate is found to be increase rapidly during the period of the active star formation. The age spread (ranging from <TEX>$5\times10^6$</TEX> yrs to <TEX>$10^7$</TEX> yrs) of stars in a given cluster appears to be real which occurs in the extremely young open clusters.
1107
- Chun, Mun-Suk
- 天文學會誌 = The journal of the Korean Astronomical Society
- 16, n.1
- pp.1-5
- 1983
- 원문 바로보기
Four HII regions of the Sd galaxy NGC 7793 were observed using AAT/IPCS. From these spectra we determined abundances of the elements using observed emission lines and electron temperatures. The calculated abundances show that this galaxy does not show any significant radial abundance gradient. The mean oxygen abundance is very much like the Orion nebulae and the nitrogen abundance is similar to the late type barred spiral galaxy NGC 1313.
1108
- Park, Young-Deuk
- 天文學會誌 = The journal of the Korean Astronomical Society
- 16, n.2
- pp.31-42
- 1983
- 원문 바로보기
Making use of a relation proposed by Wielen (1977), a new empirical relation between Call emission flux and stellar age is derived by analyzing Wilson and Woolley's spectroscopic data (1970) of late type main sequence stars (K0-M5) and kinematic properties of those stars given by Gliese (1969). The proposed relation shows that the emission flux excess of the Call H-K lines, <TEX>$F_k'+F_k'$</TEX> introduced by Linsky et al. (1979) decreases with stellar age <TEX>$\tau$</TEX> as <TEX>$\tau^{-0.51}$</TEX>, consistent with the inverse square law as noted by Skumanich (1972).
1109
- Lee, Sang-Gak
- 天文學會誌 = The journal of the Korean Astronomical Society
- 16, n.2
- pp.55-63
- 1983
- 원문 바로보기
From UBVRI photometry and space motion data of 232 late type dwarf stars, it is found that for the stars of (R-I)<0.5, <TEX>$\Delta$</TEX>(U-B) and <TEX>$\Delta$</TEX>(B-V) color excesses are correlated with their orbital eccentricities. Therefore, <TEX>$\Delta$</TEX>(U-B) and <TEX>$\Delta$</TEX>(B-V) color excesses can be used as possible photometric abundance indicators for the stars of (R-I)<0.5. For the stars of (R-I)<TEX>${\geq}$</TEX>0.5, the correlation between color excess and orbital eccentricity is not clear. However, it is interesting to note that the high orbital eccentricity stars show some blue deficiencies and these blue deficiencies seem to be correlated with orbital eccentricity.
1110
- Lee, See-Woo
- 天文學會誌 = The journal of the Korean Astronomical Society
- 16, n.2
- pp.43-54
- 1983
- 원문 바로보기
The present day mass functions of main sequence stars in the well observed open clusters, Hyades, Praesepe, Pleiades, NGC 654 and NGC 6530 arc derived and compared with those computed from the model of time-dependent initial mass function and star formation rate. The agreements between the observed and computed present day mass functions suggest the importance of fragmentation process at the early phase and fragment interaction at the later phase of cluster evolution. This process of star formation is different from that related to the evolution of the solar neighborhood, and also could explain the lack of low mass stars observed in some open clusters.