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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 82/122
811
- HIREMATH K. M.
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.313-314
- 1996
- 원문 바로보기
Assuming that the solar activity and the solar cycle phenomena may be manifestations of global torsional MHD oscillations, we compute the Alfven wave travel times along the field lines in the five models of magnetic field described in the following text. For all these models, we compute standard deviation and it's ratio to mean Alfvenic wave travel times. The last two models yield the smallest relative bandwidth for the frequencies of the MHD oscillations. However, the last model is the only admissible one which can sustain global Alfvenic oscillations with well defined frequency for the fundamental mode
812
- TOVMASSIAN H. M.
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.393-393
- 1996
- 원문 바로보기
A new concept of a simple and cheap construction of giant telescope is described.
813
- ZHANG X.
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.199-200
- 1996
- 원문 바로보기
814
- YUN H. S.
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.339-340
- 1996
- 원문 바로보기
In the present study we examine physical characteristics of a thin and rigid magnetic flux tube with a steady flow inside, which is embedded vertically upward in the solar atmosphere. We found from this study that (1) The downward material flow gives rise to a dominant heating in the flux tube which works with the conductive heating in the same direction. However, the upflow flow creates a dominant cooling which works against the conductive heating, resulting in a steeper temperature gradient with a shallower transition region. (2) Since the thickness of the transition region determines the material content in the transition region, a broader transition region of the downflow tube produces a larger differential measure.
815
- LAI S. P.
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.327-328
- 1996
- 원문 바로보기
816
- BUDDlNG E.
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.205-208
- 1996
- 원문 바로보기
Multi-wavelength observing has been particularly fruitful in cool star research. There have been some well-observed examples, eg AB Dor, though ambiguity remains. This raises issues of data information content and model parameter determinacy, which are examined firstly in an optical context. We then widen the discussion to show how multi-site and multi-wavelength data can be combined to point to better constrained models. Particular cases, involving near-simultaneous radiometry and photometry, are discussed to clarify such modelling.
817
- SHAMSHIEV FAZILIDDIN T.
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.73-74
- 1996
- 원문 바로보기
This paper deals with steady-state gravitational potentials of nonaxisymmetric three dimensional systems which rotate with a constant angular velocity. For these systems a class of potentials with local integrals has been found.
818
- LEE YOUNG-WOOK
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.49-51
- 1996
- 원문 바로보기
New population synthesis models, with the effects of metallicity spread and the horizontal-branch (HB) morphology, provide a way to break the well-known age-metallicity degeneracy in the analysis of the integrated light of elliptical galaxies. Our models suggest that the far- UV radiation of these systems is dominated by a minority population of metal-poor, hot HB stars and their post-HB progeny, while the optical radiation is dominated by a metal-rich population. The systematic variation of UV upturn depends on the contribution from metal-poor, hot HB stars and their post-HB progeny, which in turn depends on the ages of old stellar populations in galaxies. Our result implies a prolonged epoch of galaxy formation, in the sense that more massive galaxies (in denser environments) formed first. Our models also suggest that the strenghth of H<TEX>$\beta$</TEX> index is strongly affected by HB stars, and hence previous age estimation without detailed modeling of the HB would underestimate the ages of ellipticals by <TEX>$\~$</TEX>7 Gyr.
819
- CHOE SEUNG-URN
- Journal of the Korean astronomical society = 천문학회지
- 29, n.2
- pp.93-105
- 1996
- 원문 바로보기
We have solved the radiative transfer problem using a Sobolev approximation with an escape probability method in case of the supersonic expansion of a stellar envelope to an ambient medium. The radiation from the expanding envelope turns out to produce a P-Cygni type profile. In order to investigate the morphology of the theoretical P-Cygni type profile, we have treated <TEX>$V_\infty,\;V_{sto},\;\beta$</TEX> (parameters for the velocity field), it and E(parameter for collisional effect) as model parameters. We have investigated that the velocity field and the mass loss rate affect the shapes of the P-Cygni type profiles most effectively. The secondarily important factors are <TEX>$V_\infty,\;V_{sto}$</TEX>. The collisional effect tends to make the total flux increased but not so much in magnitude. We have infered some physical parameters of 68 Cyg, HD24912, and <TEX>$\xi$</TEX> persei such as <TEX>$V_\infty,\;M$</TEX> from the model calculation, which shows a good agreenment with the observational results.
820
- WEE SUN-OK
- Journal of the Korean astronomical society = 천문학회지
- 29, n.2
- pp.181-194
- 1996
- 원문 바로보기
We present a study of the metallicity of the old open cluster NGC 1245 , based on the Washington CCD photometry obtained using the 0.6 m telescope at the Sobaeksan Observatory, Korea. NGC 1245 has been known to be a unique cluster among the known open clusters in the sense that the previous metallicity estimates for this cluster are much larger <TEX>$(by\;\sigma)$</TEX> than the value expected from the radial metallicity gradient of the old open clusters in Our galaxy. We have estimated the metallicity of the cluster red giants using the four color-color diagrams, obtaining a value for the mean metallicity of <TEX>$[Fe/H] = -0.04\pm0.05$</TEX> dex. The total error including the error of the metallicity calibration, 0.15 dex, is 0.16 dex. The metallicity estimate of NGC 1245 we have obtained in this study is smaller than previous estimates, and is consistent with the radial metallicity gradient of the old open clusters, showing that the mean metallicity of NGC 1245 is not abnormally high. The reddening, distance, and age of the cluster have also been derived using the isochrones based on the convective overshooting models: the reddening <TEX>$E(B-V) = 0.28\pm0.03$</TEX>; the distance <TEX>$d = 2.5\pm0.2 kpc$</TEX> (the corresponding galactocentric distance is RGC = 10.7 kpc, and the distance from the galactic plane is z = -0.4 kpc); and the age <TEX>$t = 1.1\pm0.1 Gyrs$</TEX>.