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- 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 76/122
751
- 안영숙
- Journal of the Korean astronomical society = 천문학회지
- 33, n.3
- pp.177-183
- 2000
- 원문 바로보기
We arrange Korean ancient calendar with Solar calendar during Choseon Dynasty(A.D. 1392-1910). In this period, we have one representable history books and several books, and most of information for date are found from them, ChoseonWangjosillok(조선왕조실록) and Jeungbomunheonbigo(증보문헌비고), etc. In those books many astronomical data and calendar information data are contained, so we can make chronological tables. Most of the data are arranged based on those several books, and for doubtable data are identified from eclipse, historical events and lunar phase calculations etc. We find that arranged chronological tables during Choseon Dynasty are similar to that of China and somewhat different from that of Japan. In addition we summarize all misrecorded date data in ChoseonWangjosillok
752
- MOON Y.-J.
- Journal of the Korean astronomical society = 천문학회지
- 33, n.1
- pp.47-55
- 2000
- 원문 바로보기
Nonpotential characteristics of magnetic fields in AR 5747 are examined using Mees Solar Observatory magnetograms taken on Oct. 20, 1989 to Oct. 22, 1989. The active region showed such violent flaring activities during the observational span that strong X-ray flares took place including a 2B/X3 flare. The magnetogram data were obtained by the Haleakala Stokes Polarimeter which provides simultaneous Stokes profiles of the Fe I doublet 6301.5 and 6302.5. A nonlinear least square method was adopted to derive the magnetic field vectors from the observed Stokes profiles and a multi-step ambiguity solution method was employed to resolve the <TEX>$180^{\circ}$</TEX> ambiguity. From the ambiguity-resolved vector magnetograms, we have derived a set of physical quantities characterizing the field configuration, which are magnetic flux, vertical current density, magnetic shear angle, angular shear, magnetic free energy density, a measure of magnetic field discontinuity MAD and linear force-free coefficient. Our results show that (1) magnetic nonpotentiality is concentrated near the inversion line in the flaring sites, (2) all the physical parameters decreased with time, which may imply that the active region was in a relaxation stage of its evolution, (3) 2-D MAD has similar patterns with other nonpotential parameters, demonstrating that it can be utilized as an useful parameter of flare producing active region, and (4) the linear force-free coefficient could be a evolutionary indicator with a merit as a global nonpotential parameter.
753
- KIM HYUN-GOO
- Journal of the Korean astronomical society = 천문학회지
- 33, n.3
- pp.151-158
- 2000
- 원문 바로보기
We conducted a deep CCD observations in V band to obtain stellar density distribution and to determine the distances toward two molecular clouds with anomalous velocity in the Galactic anti-center region. Star count method based on the linear programming technique was applied to the CCD photometric data. We found two prominent peaks at distances of around 1.4 and 2.7 kpc. It is found that the first peak coincides well with stellar density enhancement of B8-A0 stars and the second one with the outer Perseus arm. The effect of the choice of the luminosity function is discussed. The stellar number density distribution is used to derive the distances to the molecular clouds and the visual extinctions caused by the clouds. We found that two molecular clouds are located almost at the same distance of about 1.1 <TEX>$\pm$</TEX> 0.1 kpc, and the peak extinctions caused by the clouds are about 2.2 <TEX>$\pm$</TEX> 0.3 mag in V band.
754
- KYEONG JAE-MANN
- Journal of the Korean astronomical society = 천문학회지
- 33, n.3
- pp.143-149
- 2000
- 원문 바로보기
We present the results of near-IR band (JHK) photometric study for the old open cluster To 2. Combined with existing optical data, our IR photometry is used to derive the reddening E(B- V)=0.24<TEX>$\pm$</TEX>0.12 and the distance (m-M)o=14.6<TEX>$\pm$</TEX>0.42. Comparison with theoretical isochrones suggests the age and metallicity of To 2 are log t<TEX>$\~$</TEX>9.3 and [Fe/H]<TEX>$\~$</TEX>-0.3, respectively.
755
- HYUNG SIEK
- Journal of the Korean astronomical society = 천문학회지
- 33, n.2
- pp.97-110
- 2000
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Planetary nebulae provide a direct way to probe elemental abundances, their distributions and their gradients in populations in nearby galaxies. We investigate bulge planetary nebulae in M 31 and M 32 using the strong emission lines, H<TEX>$\alpha$</TEX>, He I, [O III], [N II], [S II] and [Ne III]. From the [O III] 4363/5007 line ratio and the [O II] 3727/3729, we determine the electron temperatures and number densities. With a standard modeling procedure (Hyung, 1994), we fit the line intensities and diagnostic temperatures, and as a result, we derive the chemical abundances of individual planetary nebulae in M 31 and M 32. The derived chemical abundances are compared with those of the well-known Galactic planetary nebulae or the Sun. The chemical abundances of M 32 appear to be less enhanced compared to the Galaxy or M 31.
756
- KIM YONG-CHEOL
- Journal of the Korean astronomical society = 천문학회지
- 32, n.2
- pp.119-126
- 1999
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The standard stellar models for <TEX>$\alpha$</TEX> Cen A and B have been constructed without resorting to the arbitrary constraint of the Solar mixing length ratio. Assuming that the chemical compositions and the ages of the two stars are the same, series of models have been constructed. Using the observational constraints, [Z/X], we were able to constrain the number of the 'possible' models. We find that utilizing the observational constraints of [Z/X] the best models for <TEX>$\alpha$</TEX> Cen system are with the initial Z = 0.03, X = 0.66<TEX>$\~$</TEX>0.67. In particular, the primary and the secondary stars may have the same mixing length ratio 1.6<TEX>$\~$</TEX>1.7, which is the same as that of the calibrated Solar model. And, the age of the system is about 5.4 Gyr. Finally, the large spacing of the p-modes is predicted to be 104 <TEX>$\pm$</TEX> 4<TEX>$\mu$</TEX>Hz for <TEX>$\alpha$</TEX> Cen A.
757
- HYUNG SIEK
- Journal of the Korean astronomical society = 천문학회지
- 32, n.1
- pp.55-63
- 1999
- 원문 바로보기
NGC 6537 is an extremely high excitation bipolar planetary nebula. It exhibits a huge range of excitation from lines of [N I] to [Si VI]or [Fe VII], i.e. from neutral atoms to atoms requiring an ionization potential of <TEX>$\~$</TEX>167eV. Its kinematical structures are of special interest. We are here primarily concerned with its high resolution spectrum as revealed by the Hamilton Echelle Spectrograph at Lick Observatory (resolution <TEX>$\~0.2{\AA}$</TEX>) and supplemented by UV and near-UV data. Photoionization model reproduces the observed global spectrum of NGC 6537, the absolute H<TEX>$\beta$</TEX> flux, and the observed visual or blue magnitude fairly well. The nebulosity of NGC 6537 is likely to be the result of photo-ionization by a very hot star of <TEX>$T_{eff} \~ 180,000 K$</TEX>, although the global nebular morphology and kinematics suggest an effect by strong stellar winds and resulting shock heating. NGC 6537 can be classified as a Peimbert Type I planetary nebula. It is extremely young and it may have originated from a star of about 5 <TEX>$M_{\bigodot}$</TEX>.
758
- KIM K.-T.
- Journal of the Korean astronomical society = 천문학회지
- 32, n.2
- pp.75-82
- 1999
- 원문 바로보기
Diffuse radio emission in Abell 2256 was detected above 3 <TEX>$\sigma$</TEX> with DRAO observations at 1420 MHz. The halo size is <TEX>$\~13' {\times}10' (\~1h^{-1}_{50}\;Mpc$</TEX>) in full extent and is elongated along a position angle of about <TEX>$112^{\circ}$</TEX>. The total flux density contained in the halo is 30<TEX>$\pm$</TEX>10 mJy at 1420 MHz and its spectral index is -2.04<TEX>$\pm$</TEX>0.04, showing no evidence for steepening up to 1420 MHz. Using the size estimate, yields a more reliable equipartition magnetic field strength which is <TEX>$0.34(1 + k)^{2/7}{\mu}G$</TEX>. In addition, five new radio sources are identified.
759
- KIM YOUNG KWANG
- Journal of the Korean astronomical society = 천문학회지
- 32, n.1
- pp.17-39
- 1999
- 원문 바로보기
We investigate dynamical evolution of globular clusters with multi-mass component under the Galactic tidal field. We compare the results with our previous work which considered the cases of single-mass component m the globular clusters. We find the followings: 1) The general evolutions are similar to the cases of single-mass component. 2) There is no evidence for dependence on the orbital phase of the cluster as in the case of single-mass component. 3) The escape rate in multi-mass models is larger than that in the single-mass models. 4) The mass-function depends on radius more sensitively in anisotropic models than in isotropic models.
760
- MOON YONG-JAE
- Journal of the Korean astronomical society = 천문학회지
- 32, n.2
- pp.127-136
- 1999
- 원문 바로보기
In this study we present the study of solar active regions based on BOAO vector magnetograms and H<TEX>$\alpha$</TEX> filtergrams. With the new calibration method we analyzed BOAO vector magnetograms taken from the SOFT observational system to compare with those of other observing systems. In this study it has been demonstrated that (1) our longitudinal magnetogram matches very well the corresponding Mitaka's magnetogram to the extent that the maximum correlation yields r=0.962 between our re-scaled longitudinal magnetogram and the Mitaka's magnetogram; (2) according to a comparison of our magnetograms of AR 8422 with those taken at Mitaka solar observatory their longitudinal fields are very similar to each other while transverse fields are a little different possibly due to large noise level; (3) main features seen by our longitudinal magnetograms of AR 8422 and AR 8419 and the corresponding Kitt Peak magnetograms are very similar to each other; (4) time series of our vector magnetograms and H-alpha observations of AR 8419 during its flaring (M3.1/1B) activity show that the filament eruption followed the sheared inversion line of the quadrupolar configuration of sunspots, indicating that the flare should be associated with the quadrupolar field configuration and its interaction with new filament eruption. Finally, it may be concluded that the Solar Flare Telescope at BOAO works normally and it is ready to do numerous observational and theoretical works associated with solar activities such as flares.