• Publications of The Korean Astronomical Society
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• v.37 no.2
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• pp.13-31
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• 2022

We observed the symbiotic star AG Dra for a total of 61 nights between April 2004 and December 2021 using the 1.8-m telescope and the high-resolution Echelle spectrograph BOES at the Bohyunsan Optical Astronomy Observatory and obtained 355 frames of spectroscopic data to investigate the variations in its spectral lines. Overnight short-term and long-term changes in prominent emission lines are examined. No short-term changes are found in the line profiles. However, the peak intensity of the Hα emission line exhibits very small variation. In the long-term period, many emission lines including He I λ5875, λ6678, λ7065 and Fe II λ5018 are found to vary reflecting the symbiotic outburst activities. It is noted that He II λ4686 and Raman-scattered O VI λ6830, λ7088 are exceptions, where no significant variations are discernible. One of the noticeable lines is the λ5018 line. Its appearance and disappearance pattern are different from other emission lines, and the line is found to appear in outburst states. The Hα and Hβ lines remain very similar in our spectroscopic monitoring campaign.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.230-235
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• 1997

During laser welding, a laser induced matal vapour and plasuma is formed. The plasma shows strong fluctuation combined with acoustic sound emission. On-line monitoring of the process is possible by measuring and analysing the plasma and acoustic sound emission. This paper introduce the method of on line process monitoring in the laser beam welding and analysis being monitoring signal. The results show the complementary information on the process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.8
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• pp.634-639
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• 2001

We investigated the etching characteristics of chromium films by using Cl$_2$/O$_2$ gas mixtures with electron cyclotron resonance plasma. In order to examine the chemical etch characteristics of Cr films by using Cl$_2$/O$_2$ gas plasma, we obtained the etch rate with various gas mixing ratios. By X-ray photoelectron spectroscopy, the surface reaction on the chromium films during the etch was examined. From narrow scan analyses of Cr, Cl, and O, it was confirmed that a chromium oxychlorie (CrCl$_{x}$O$_{y}$) layer was formed on the surface by the etch using Cl$_2$/O$_2$ gas mixtures. We observed a new characteristic emission line during the etch of chromium films using Cl$_2$/O$_2$ gas mixtures by an optical emission spectroscopy. It was found that the peak intensity of this emission line had a tendency compatible with the etch rate. The origin of this emission line was discussed in detail. At the same time, the etched profile was also examined by scanning electron microscope.e.e.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.43.2-44
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• 2020

We have carried out high-resolution near-infrared (NIR) spectroscopic observations toward 16 Galactic supernova remnants (SNRs) showing strong H2 emission features. A dozen bright H2 emission lines are clearly detected for individual SNRs, and we have measured their central velocities, line widths, and fluxes. For all SNRs except one (G9.9-0.8), the H2 line ratios are well consistent with that of thermal excitation at T~2000 K and their line widths are broader than ~10 km s-1, indicating that the H2 emission lines are most likely from shock-excited gas and therefore that they are physically associated with the remnants. The kinematic distances to the 15 SNRs are derived from the central velocities of the H2 lines using a Galactic rotation model. We derive for the first time the kinematic distances to four SNRs: G13.5-0.2, G16.0-0.5, G32.1-0.9, G33.2-0.6. Among the rest 11 SNRs, the central velocities of the H2 emission lines for six SNRs are well consistent (±5 km s-1) with those obtained in previous radio observations, while for the other five SNRs (G18.1-0.1, G18.9-1.1, Kes 69, 3C 396, W49B), they are significantly different. We discuss the velocity discrepancies in these five SNRs. In G9.9-0.8, the H2 emission shows non-thermal line ratios and very narrow line width (~4 km s-1), and we discuss its origin.

• Bulletin of the Korean Space Science Society
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• 2004.04a
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• pp.26-26
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• 2004

We compare the distribution of HI 21cm, HII 6563 AA, and CII 157.7 micron m line emission over the entire Large Magellanic Cloud (LMC). Bright CII emission is associated with HII regions and their surroundings, with a good correlation between CII and Halpha filaments. Diffuse CII emission is also detected in regions with no HII emission. We found a reasonably good correlation between the extended CII emission and HI emission. (omitted)

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.64.1-64.1
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• 2013

High energy photons and mechanical energy produced by the process of star formation result in copious FIR molecular and atomic lines, which are important coolants of the system. Photons thermally or mechanically induced could dissociate water in the dense envelope to change relative abundances among the species O, OH, and H2O. Here we analyze OH emission lines toward embedded young stellar objects (YSOs) observed as part of the Herschel open time key program, 'Dust, Ice, and Gas In Time (DIGIT)' in order to study the physical conditions of associated gas and the energy budget loaded on the OH line emission. According to our analysis of the Herschel/PACS spectra, OH emission peaks at the central spaxel in most of sources, but several sources show spatially extended emission structures. In the extended emission sources, the distribution of OH emission is correlated with that of [OI] emission and extended along the outflow directions. Considering the diversity of source properties, ratios between detected OH lines are relatively constant among sources. In addition, each OH line has strong correlation with bolometric luminosity. For detail analyses with rotation diagram and non-LTE LVG model, we present the results from GSS30-IRS1 and Elias29.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.61.2-61.2
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• 2011

Low-ionization nuclear emission-line regions (LINERs) have been generally regarded to be powered by active galactic nuclei (AGNs), yet still a number of alternative explanations on the origin of LINER emission are suggested; for example, planetary nebulae nuclei of massive stars, supernovae shocks from death of massive stars, and old stellar populations. Interestingly, a majority of recent star formation early-type galaxies (ETGs) in local universe presents such LINER emission lines. Given that situation, revealing the true nature of LINERs is a crucial step to constrain the evolution path to quiescent ETGs. To resolve the issue, we use Keck/LRIS to obtain spatially resolved spectra on a carefully selected ETG. The ETG SDSS J091628.05+420818.7 at redshift z ~ 0.024 shows modest LINER emission line features without any detection of 21 cm radio continuum nor X-ray emission. We perform a stellar continuum subtraction and measure emission line strengths and their uncertainties for each spectrum from five apertures along the slit with size of 1 arcsecond (~0.5 kpc). We find that extended spatial distributions of four emission lines $H{\alpha}$, $H{\beta}$, [OIII]${\lambda}5007$, and [NII]${\lambda}6583$, and they can be explained by central emission blurring effect. We conclude that the emissions seem to be centrally concentrated, indicating the AGN-nature of LINERs.

• Journal of The Korean Astronomical Society
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• v.36 no.2
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• pp.55-60
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• 2003

In Lee, Kang & Byun (2001) the discovery of Raman scattered 6545 A feature was reported in symbiotic stars and the planetary nebula M2-9. The broad emission feature around 6545 A is formed as a result of Raman scattering of He II n = 6 $\to$ n = 2 photons by atomic hydrogen. In this paper, we introduce a method to compute the equivalent width of He II $\lambda$ 1025 line and present an optical spectrum of the symbiotic star RR Telescopii as an example for a detailed illustration. In this spectrum, we pay attention to the broad H$\alpha$ wings and the Raman scattered He II 6545 feature. The broad Ha wings are also proposed to be formed through Raman scattering of continuum around Ly$\beta$ by Lee (2000), and therefore we propose that the equivalent width of the He II $\lambda$ 1025 emission line is obtained by a simple comparison of the strengths of the 6545 feature and the broad H$\alpha$ wings. We prepare a template H$\alpha$ wing profile from continuum radiation around Ly$\beta$ with the neutral scattering region that is supposed to be responsible for the formation of Raman scattered He II 6545 feature. Isolation of the 6545 feature that is blended with [N II] $\lambda$ 6548 is made by using the fact that [N II] $\lambda$ 6584 is always 3 times stronger than [N II] $\lambda$ 6548. We also fit the 6545 feature by a Gaussian which has a width 6.4 times that of the He II $\lambda$ 6527 line. A direct comparison of these two features for RR Tel yields the equivalent width $EW_{Hel025} = 2.3{\AA}$ of He II $\lambda$ 1025 line. Even though this far UV emission line is not directly observable due to heavy interstellar extinction, nearby He II lines such as He II $\lambda$ 1085 line may be observed using far UV space instruments, which will verify this calculation and hence the origins of various features occurring in spectra around H$\alpha$.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.36.2-36.2
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• 2019

Fe II emission is a prominent and ubiquitous feature in the spectra of broad-line Active Galactic Nuclei (AGN) by producing a pseudo-continuum from UV to optical with complex and strong blends of the numerous emission lines themselves, other emission lines, and continuum. Since theoretical modeling of such intricate Fe II emission is very difficult and still far from able to reproduce observed data in detail, an empirical iron emission template, derived from observations of a narrow-line Seyfert 1 galaxy, is an essential and practical tool to obtain accurate measurements of all the emission lines and continuum in AGN spectra. However, the existing iron templates, based on the single prototypical strong Fe II emitter I Zw 1, are suffering from inadequate S/N and non-simultaneous, inconsistent data with limited wavelength coverage, which consequently limit the accuracy of all the spectral measurements. To overcome the limitations and construct an improved iron template with wide spectral coverage, high-quality UV and optical spectra for the new and better identified template galaxy, Mrk 493, were successfully obtained from our HST STIS program (GO-14744). We will show the preliminary results for multicomponent spectral decomposition of the data and template construction with application tests to various AGN spectra and comparison with previous templates.

• Journal of Korean Vacuum Science & Technology
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• v.5 no.1
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• pp.7-10
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• 2001

Ion induced secondary electron emission coefficients γ of protecting layers of an AC plasma display panel(AC-PDP) have been measured. In order to solve the surface charging effect during the measurement at insulating samples like MgO, a new method with the patterned gold line charge neutralization has been introduced. The measurement was performed at the samples, MgO and MgO+MgF$_2$, which showed a great difference in the firing voltage between the two protecting layers. The γ value has been compared with the firing voltage Vf of the AC-PDP with the same protecting layer. Correct relationship between γ and Vf has been observed. Thus, the patterned gold line method has been proven to be successful for the measurement of the secondary electron emission yield at insulator sample surfaces.