• Journal of the Korean earth science society
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• v.29 no.5
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• pp.419-427
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• 2008

The Galactic planetary nebulae emit many strong recombination and forbidden lines. By analyzing such lines, the physical condition of the planetary nebulae has been inferred using the strategically important diagnostic line ratios. In order to fully understand the physical condition of a planetary nebula and to derive its chemical abundances, the photoionization model codes, e.g., CLOUDY and NEBULA, were employed for an analysis of gaseous nebular spectra. For the well-studied, relatively simple planetary nebula NGC 7026, theoretical investigation was done with about the same input parameters in models. The predictions made by both codes seem to be in good accord. However, the predicted physical conditions, such as electron temperature and density, are slightly different. Especially, the electron temperatures are predicted to be higher in CLOUDY, which may cause a problem in chemical abundance determination. Our analysis shows that the main discordance may occur due to the diffuse radiation.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.59.2-59.2
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• 2010

The structures of the protoplanetary nebula have been examined under various conditions of the stellar wind and the mass distribution of the nebula by assuming that the nebula is steady and geometrically thick. T Tauri stars commonly accompany with disks as well as the stellar wind. Therefore, the nebula around T Tauri stars should be influenced by the stellar wind. The results are summarized as follows ; The height of the geometrical surface of the nebula is suppressed by the dynamical pressure of the wind but depends very weakly on the wind strength. The surface becomes higher slightly when the wind strength becomes weaker. Furthermore, the dependency of the nebular height on the mass distribution of the nebula is also weak. As a natural result of the above, the temperature distribution in the nebula is insensitive to the wind strength and the mass distribution of the nebula, too. Thus, we can conclude that the temperature and geometrical surface height of the nebula under the stellar wind does not depend on neither the wind properties nor the mass distribution of nebula.

• Journal of The Korean Astronomical Society
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• v.32 no.1
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• pp.55-63
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• 1999

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 $\~$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 $\~0.2{\AA}$) and supplemented by UV and near-UV data. Photoionization model reproduces the observed global spectrum of NGC 6537, the absolute H$\beta$ 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 $T_{eff} \~ 180,000 K$, 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 $M_{\bigodot}$.

• Journal of The Korean Astronomical Society
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• v.37 no.4
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• pp.273-279
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• 2004

Chemical compositions of planetary nebulae are of interest for a study of the late stage of stellar evolution and for elemental contributions to the interstellar medium of reprocessed elements since possibly a large fraction of stars in 0.8 - 8 $M_{\bigodot}$ range go through this stage. One of the methods for getting chemical composition is a construction of theoretical photoionization models, which involves geometrical complexities and a variety of physical processes. With modelling effort, one can analyze the high dispersion and find the elemental abundances for a number of planetary nebulae. The model also gives the physical parameter of planetary nebula and its central star physical parameter along with the knowledge of its evolutionary status. Two planetary nebulae, NGC 7026 and Hu 1-2, which could have evolved from about one solar mass progenitor stars, showed radically different chemical abundances: the former has high chemical abundances in most elements, while the latter has extremely low abundances. We discuss their significance in the light of the evolution of our Galaxy.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.80.1-80.1
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• 2012

NGC 6803 is an elliptical ring shape planetary nebula. We analyzed the high dispersion spectra which had been observed with the Hamilton Echelle Spectrograph attached to the 3-m Shane telescope of Lick Observatory. We also investigated the low dispersion UV spectral data obtained with the 60-cm interstellar ultraviolet explorer. Diverse excitation lines were found from neutral to quadruply ionized ions. The temperature diagnostic lines indicate relatively low electron temperatures, i.e., $T_{\epsilon}{\leq}9500$ K for most lines except for [ClIV] - 11,500 K. In spite of its simplistic bi-laterally symmetrical elliptical shape, the nebula appears to be very complex of a hugh density range from 1300 to 80,000 $cm^3$. A comparison of the two epoch data suggests that the density increase occurred in the high excitation line zone near the inner boundary. We derived the chemical abundances of He, C, N, O, Ne, S, Ar, Cl, and K. The chemical abundances of NGC 6803 are enhanced compared with the average Galactic planetary nebula. Our self-consistent photo-ionization model study implies that the effective temperature of the central star is 90,000 K and its luminosity is 2400 $L_{\odot}$. The evolutionary track suggests that the progenitor of NGC 6803 was about 0.9 -- 1.0 $M_{\odot}$ star, which might be born from a metal-rich zone near the galactic disk, but now relocated into the present high Galactic latitude.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.375-379
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• 2015

Planetary nebula in elliptical galaxies pose a problem in dark matter theory. Using data from the Planetary Nebula Spectrograph (PN. S), Romanowsky et al. (2003) reported that less dark matter than expected was found within 5 to 6 effective radii of three elliptical galaxies. We attempt to explain similar observations of elliptical galaxies with MOdified Newtonian Dynamics (MOND). We collect 16 elliptical galaxies with planetary nebulae from the public web data of PN. S. We investigate the dynamical behavior by analyzing the line-of-sight velocity dispersion in the framework of MOND.

• The Bulletin of The Korean Astronomical Society
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• v.26 no.1
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• pp.36.1-36.1
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• 2001

• Journal of the Korean earth science society
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• v.30 no.5
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• pp.611-621
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• 2009

Using the spectroscopic data secured with the Hamilton Echelle Spectrograph at Lick Observatory, we found the physical condition of the planetary Nebula NGC 6210. The spectral line profiles of the permitted and forbidden lines have been analyzed using IRAF and StarLink/Dipso. The hydrogen number densities ($N_H$) are 2,000-20,000 $cm^{-3}$, and the electron temperatures are 8,100-10,300 K based on the forbidden lines. The expansion velocities, derived from the Full Width at Half Maximum (FWHM) and the double peak of the line profiles, are in the range of 10 to $45\;kms^{-1}$. The expansion velocities imply a shell structure with an accelerated nebular gas. We also derived abundances from the permitted lines of CII, CIII, NII, NIII, OII, and OIII, which may have been formed through the fluorescence mechanism. NGC 6210 is likely to be evolved from a progenitor of more than $3M_{\bullet}$, which had been born near the Galactic plane.

• Journal of The Korean Astronomical Society
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• v.37 no.4
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• pp.269-272
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• 2004

We present the first results of a wide field survey for planetary nebulae throughout M31 undertaken at the KPNO 0.9m telescope with the Mosaic camera. So far, images in [O III]$\lambda$5007 and its continuum filter have been analyzed. Our survey appears to be at least $90\%$ complete to about 2 mag below the peak of the planetary nebula luminosity function. Over 900 planetary nebulae candidates have been found within a 12 square degree area.

• The Bulletin of The Korean Astronomical Society
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• v.26 no.1
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• pp.49.1-49.1
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• 2001