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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 74/119
731
- HYUNG SIEK
- Journal of the Korean astronomical society = 천문학회지
- 33, n.2
- pp.97-110
- 2000
- 원문 바로보기
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.
732
- KIM YONG-CHEOL
- Journal of the Korean astronomical society = 천문학회지
- 32, n.2
- pp.119-126
- 1999
- 원문 바로보기
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.
733
- 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>.
734
- 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.
735
- 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.
736
- 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.
737
- ANN HONG BAE
- Journal of the Korean astronomical society = 천문학회지
- 32, n.2
- pp.83-89
- 1999
- 원문 바로보기
We have conducted a V, I, J, and H surface photometry of a barred galaxy NGC 4314 to analyze the morphology and luminosity distribution of the galaxy. By applying a semi two-dimensional profile decomposition method, we derived the luminosity fractions and the scale lengths of the three distinct components, bulge, disk, and bar: <TEX>$L_b {\approx}0.35,\;L_d{\approx}0.35,\;L_{bar}{\approx}0.30,\;r_e{\approx}22',\;r_o {\approx} 50'$</TEX>, and a <TEX>$\approx$</TEX> 60'. The bulge of NGC 4314 seems to be triaxial due to the isophotal twists but its luminosity distribution is well approximated by the <TEX>$r^{1/4}$</TEX>-law.
738
- LEE JEONG-EUN
- Journal of the Korean astronomical society = 천문학회지
- 32, n.1
- pp.41-53
- 1999
- 원문 바로보기
We have carried out high-resolution observations along one-dimensional cuts through the three Galactic super-shells GS 064-01-97, GS 090-28-17, and GS 174+02-64 in the HI 21 cm and CO J=l-0 lines. By comparing the HI data with IRAS data, we have derived the distributions of the <TEX>$I_{100}$</TEX> and <TEX>$T_{100}$</TEX> excesses, which are, respectively, the 100 <TEX>${\mu}m$</TEX> intensity and 100 <TEX>${\mu}m$</TEX> optical depth in excess of what would be expected from HI emission. We have found that both the <TEX>$I_{100}$</TEX> and <TEX>$T_{100}$</TEX> excesses have good correlations with the CO integrated intensity W co in all three supershells. But the <TEX>$I_{100}$</TEX> excess appears to underestimate <TEX>$H_2$</TEX> column density N(<TEX>$H_2$</TEX>) by factors of 1.5-3.8. This factor is the ratio of atomic to molecular infrared emissivities, and we show that it can be roughly determined from the HI and IRAS data. By comparing the <TEX>$T_{100}$</TEX> excess with <TEX>$W_{co}$</TEX>, we derive the conversion factor X <TEX>$\equiv$</TEX> N (<TEX>$H_2$</TEX>) /<TEX>$W_{co}{\simeq}$</TEX> 0.26 - 0.66 in the three supershells. In GS 090- 28-17, which is a very diffuse shell, our result suggests that the region with N(<TEX>$H_2$</TEX>) <TEX>$\le$</TEX> <TEX>$3 {\times} 10^{20} cm^{-2}$</TEX> does not have observable CO emission, which appears to be consistent with previous results indicating that diffuse molecular gas is not observable in CO. Our results show that the molecular gas has a 60/100 <TEX>${\mu}m$</TEX> color temperature <TEX>$T_d$</TEX> lower than the atomic gas. The low value of <TEX>$T_d$</TEX> might be due either to the low equilibrium temperature or to the lower abundance of small grains, or a combination of both.
739
- ANN HONG BAE
- Journal of the Korean astronomical society = 천문학회지
- 32, n.1
- pp.1-6
- 1999
- 원문 바로보기
We have conducted near-infrared (J- and H-band) surface photometry for two early type barred galaxies, NGC 3412 and NGC 3941. The bulges of NGC 3412 and NGC 3941 show isophotal twists which indicate that they are triaxial. NGC 3412 has a very short bar and its bulge is more centrally concentrated than that of NGC 3941. The unusually short bar and the centrally concentrated triaxial bulge of NGC 3412 might be the result of bar dissolution. The colors of the nuclear region of NGC 3941 resemble those of the blue nuclei, implying the presence of young stellar populations.
740
- SUNG HWANKYUNG
- Journal of the Korean astronomical society = 천문학회지
- 32, n.2
- pp.109-117
- 1999
- 원문 바로보기
UBVI CCD photometry has been obtained for a region around the Wolf-Rayet star WR 12. We found two young stellar associations in the observed field: the nearer one comprises the field members of Vela OBI association at d = 1.8kpc, while the farther one is the young open cluster Bochum 7 (Bo 7) at d = 4.8kpc. The stars associated with Bo 7 showed no central concentration which suggests that Bo 7 is not a young open cluster but simply a local concentration in the density of young stars belonging to the OB association (Vel OB3). These two associations have similar ages but remarkably different mass function slopes (<TEX>$\Gamma$</TEX> = -2.1 <TEX>$\pm$</TEX> 0.3 for Vel OBI and -1.0 <TEX>$\pm$</TEX> 0.3 for Bo 7). The stars in Vel OBI shows an evident age spread (<TEX>${\Delta}T\~ 9Myr$</TEX>). We also found two strong H<TEX>$\alpha$</TEX> emission stars - WR 12 and <TEX>$\sharp$</TEX>1066 - from narrow band H<TEX>$\alpha$</TEX> photometry.