• 한국지구과학회:학술대회논문집
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• 2010.04a
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• pp.121-121
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• 2010

행성상 성운 NGC 7009와 NGC 7027의 모델을 연구하기 위해 1998년 8월 14일부터 16일 까지 3일간의 Keck I HIRES의 분광 관측 자료를 이용하였다. 사용한 파장 영역은 $3250{\AA}{\sim}8725{\AA}$이고, H I, He I, He II, C II, C III, N II, N III, [N II], [O I], [O II], [O III], [S II], [S III], [Cl III], [Cl IV], [Ar III], [Ne III] 등의 방출선을 얻었다. 본 연구에서는 이러한 방출선의 선윤곽(line profile)을 IRAF와 StarLink/Dipso를 이용해 분석하여 성분을 구하였는데 H I, He I, He II, [O III], [C III], [N II] 등 대부분은 2개로 분리되었고, [S II], [Ar III]의 경우에는 3개로 분리되었다. 후자의 경우 구각(shell)의 단순한 팽창뿐만 아니라 다른 제3의 방향으로 팽창하고 있는 성분이 존재함을 의미한다. 비교적 S/N가 양호한 선들의 FWHM(Full Width at Half Maximum)을 측정하여 팽창속도를 구한 후 이 선들이 생성에 기여한 지역의 온도 또는 이온화 에너지 (IP)에 대한 팽창속도의 변화를 조사하였다. 또한 두 행성상 성운의 물리적 특성과 화학 원소 함량을 결정하기위해 광이온 모델 Tlusty Code와 CLOUDY를 사용하여 NGC 7009의 선행연구 Hyung & Aller(1995), Kwitter & Henry(1998)와 비교하였고, NGC 7027은 Zhang & Liu(2005), Middlemass(1990)와 비교하였다. NGC 7009과 NGC 7027의 수소 밀도($N_H$)를 $8,000cm^{-3}$으로 가정했을 때, NGC 7009의 중심별의 온도는 77,000K이고, 구각(shell)의 크기는 0.031~0.044pc이며 장축에 대해서만 결과를 나타내었다. NGC 7027의 경우, 중심별의 온도는 180,000K이고, 구각(shell)의 크기는 0.015~0.02pc으로 판단된다.

• Bulletin of the Korean Space Science Society
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• 2001.11a
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• pp.55-55
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• 2001

• Bulletin of the Korean Space Science Society
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• 2001.11a
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• pp.52-52
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• 2001

• 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.36 no.2
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• pp.115.1-115.1
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• 2011

We analyzed the line profiles of the planetary nebula (PN) NGC 7009 secured with the Keck I HIES and BOES's spectral data. The 5 positions were taken over the nebular image, 4 points on the bright rim plus 1 point at the central position. The covered spectral wavelength range was $3250{\AA}-8725{\AA}$ in these observations. We decomposed the lines of HI, HeI, HeII, CII, NIII, [ClIII], [NII], [OII], [OIII], [SII], [SIII], [ClIII], and [ArIII] using the IRAF and StarLink/Dipso. After correcting the Earth's movement and the PN's radial velocities, -48.6 & -48.9 km/s, respectively, for the Keck & BOES, we produced the line profiles in a velocity scale. The zero velocity at each line profile clearly indicates which part of the components is approaching or receding, giving a general information of the kinematical structure. Almost all of the low-to-medium excitation lines, such as [NII], [SII], [O III], and [ArIII], secured at the central position and four positions along the major & minor axes, showed 3 components, double peak + a wide wing component, suggesting the fast outflow structures are present. The overall geometry is a prolate shell which also has a fainter outer shell in the halo zone, but there appears to be some peculiar sub-structures inside the main shell. The high excitation He I, HeII, NIII lines which might be formed close to the inner boundary of the shell show unusual features, completely different from the other lines. The HeII and these high excitation lines may be indicative of a relative recent fast outflow from the central star and the permitted lines such as NIII might be affected by the innermost structure. We discuss a possible presence of a jet-like fast outflow structure in an out-flow axis different from the main axis of the spheroid shell.