• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.161-164
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• 2012

We performed a spectroscopic survey for cometary volatiles with the Infrared Camera onboard the Japanese infrared satellite AKARI. The observations were carried out in the near-infrared wavelength range in the period from 2008 June to 2010 January. In this paper, we summarize the observations and results of the AKARI survey for the mixing ratios of major volatiles in comets. We derived the $2.5-5{\mu}m$ spectra of 18 comets including both Oort cloud comets and Jupiter-family comets. Prominent emission bands in the observed spectra are the fundamental vibrational bands of water ($H_2O$) at $2.7{\mu}m$ and carbon dioxide ($CO_2$) at $4.3{\mu}m$. The fundamental vibrational band of carbon monoxide (CO) at $4.7{\mu}m$ and the broad emission feature probably related to C-H bearing molecules can also be recognized around the $3.4-3.5{\mu}m$ region in some comets. We detect $CO_2$ in 17 out of 18 comets, and derived gas production rate ratios of $CO_2$ with respect to $H_2O$ in 17 comets. We detect a reliable CO emission band only in three of the comets. Our data set provides the largest homogeneous database of $CO_2/H_2O$ ratios in comets obtained so far.

• Journal of Astronomy and Space Sciences
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• v.18 no.2
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• pp.101-108
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• 2001

Low resolution spectroscopic observations of leo-stationary satellites over the Korean peninsula have been carried out at the KyungHee Optical Satellite Observing Facility (KOSOF) with a 40cm telescope. We have observed 9 telecommunication satellites and 1 weather satellite of 6 countries. The obtained spectral data showed that satellites could be classified and grouped with similar basic spectral feature. We divided the 10 satellites into 4 groups based on spectral slop and reflectance. It is suggested that the material types of the satellites can be determined through spectral comparisons with the ground laboratory data. We will continuously observe additional geo-stationary satellites for the accurate classification of spectral features.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.24.1-24.1
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• 2009

V994 Her(ADS 11373 AB, HIP 90483) has been recently known as a quadruple system which consists of double eclipsing and double double-lined spectroscopic binaries (Lee et al. 2008). BV CCD photometric observations of the intricate star system were made during the observing seasons from 2007 to 2008 with the 35cm reflector of the Campus station of the Chungbuk National University Observatory. From the observations a total of 10 times of minimum lights were newly determined. All timings collected, including ours, were intensively analyzed to yield new interesting findings: 1) two eclipsing binaries with the orbital periods of 2.d08326 and 1.d42001 in V994 Her system show possibly apsidal motions with different apsidal periods of 46.y4 and 15.y3, and eccentricities of 0.058 and 0.082, respectively. 2) a light-time effect with a period of 0.y93 may be possible, implying that a third-body be revolving around the binary with the orbital period of 2.d08326.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.283-287
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• 2015

Within the context of the hugely successful SAGE-LMC and SAGE-SMC surveys, Spitzer photometry observations of the Large and Small Magellanic Clouds have revealed millions of infrared point sources in each galaxy. The brightest infrared sources are generally dust producing and mass-losing evolved stars, and several tens of thousands of such stars have been classified. After photometrically classifying these objects, the dust production by several kinds of evolved stars - such as Asymptotic Giant Branch stars and Red Supergiants - can be determined. SAGE-Spec is the spectroscopic follow-up to the SAGE-LMC survey, and it has obtained Spitzer-IRS $5-40{\mu}m$ spectroscopy of about 200 sources in the LMC. Combined with archival data from other programs, observations at a total of ~1000 pointings have been obtained in the LMC, while ~250 IRS pointings were observed in the SMC. Of these, a few hundred pointings represent dust producing and mass-losing evolved stars, covering a range in colors, luminosities, and thus mass-loss rates. Red Supergiants and O-rich and C-rich AGB stars - the main dust producers - are well represented in the spectroscopic sample. This paper will summarize what we know about the mineralogy of dust producing evolved stars, and discuss their relative importance in the total dust budget.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.443-445
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• 2015

We provide results of near-infrared (NIR) spectroscopic observations of 83 nearby (0.002< z <0.48) and bright (K <14 mag) type 1 active galactic nuclei (AGNs). For the observations, we used the Infrared Camera (IRC) on AKARI allowing us to obtain the spectrum in the rarely studied spectral range of $2.5-5.0{\mu}m$. The $2.5-5.0{\mu}m$ spectral region suffers less dust extinction than ultra violet (UV) or optical wavelength ranges, and contains several important emission lines such as $Br{\beta}$ ($2.63{\mu}m$), $Br{\alpha}$ ($4.05{\mu}m$), and polycyclic aromatic hydrocarbon (PAH; $3.3{\mu}m$). The sample is selected from the bright quasar surveys of Palomar Green and SNUQSO, and AGNs with black hole (BH) masses estimated from reverberation mapping method. We measure the Brackett line properties for 11 AGNs, which enable us to derive BH mass estimators and investigate circum-nuclear environments. Moreover, we perform spectral modeling to fit the hot and warm dust components by adding photometric data from SDSS, 2MASS, WISE, and ISO to the AKARI spectra, and estimate hot and warm dust temperatures of ~1100K and ~220 K, respectively.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.78.2-78.2
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• 2021

We present high resolution spectroscopic observations of transverse magnetohydrodynamic (MHD) waves in mottles located near the solar disk center. Different from previous studies that used transversal displacements of the mottles in the imaging data, we investigated the line-of-sight (LOS) velocity oscillations of the mottles in the spectral data. The observations were carried out by using the Fast Imaging Solar Spectrograph of the 1.6 meter Goode Solar Telescope of Big Bear Solar Observatory. Utilizing the spectral data of the Hα and Ca II 8542 Å lines, we measure the LOS velocity of a quiet region including the mottles and rosettes that correspond to the footpoints of the mottles. Our major findings are as follows: (1) Alfvénic waves are pervasive in the mottles. (2) The dominant period of the waves is 2 to 4 minutes. (3) From the time-distance maps of the three-minute filtered LOS velocity constructed along the mottles, it is revealed that the transverse waves in the mottles are closely related to the longitudinal waves in the rosettes. Our findings support the notion that Alfvénic waves can be generated by mode conversion of the slow magnetoacoustic waves as was shown in sunspot regions by Chae et al. (2021).

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.171-175
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• 2012

Spectroscopic studies of extragalactic YSOs have shown a great progress in the last few years. Infrared observations with AKARI made significant contributions to that progress. In this proceeding, we are going to introduce our current research on the infrared observations of ices and dust around embedded YSOs in the Magellanic Clouds.

• Journal of Astronomy and Space Sciences
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• v.29 no.1
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• pp.63-67
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• 2012

Observations with milliarsecond resolution using the Navy Optical Interferometer have been obtained for a number of stellar systems which include high-mass binaries, eclipsing binaries, and radio stars. These observations also reveal the previously unseen companions in single-lined spectroscopic binaries via directly measured flux ratios. We will present examples of published and ongoing research efforts of these systems to illustrate how an optical interferometer contributes to our knowledge of stars, their environment, and companions. These studies include a conclusive revealing of the previously unseen companion in the single-lined binary ${\Phi}$ Herculis, the direct determination of orbital parameters in the wide and close orbits of Algol, and revealing the orbit of ${\beta}$ Lyrae with spatially resolved images of the $H{\alpha}$ emission.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.263-274
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• 2004

High resolution spectroscopic observations of BX And using the BOBS (Bohyunsan Optical Echelle Spectrograph) of Bohyunsan Optical Astronomical Observatory (BOAO) were performod during 26-27, Feb. 2003. From the observations, we obtained 38 line spectra of BX And which cover all phases except the phase interval between $0.^p1$ and $0.^p3$. Both methods of the CCF (Cross-Correlation Function) and BF (Broadening Function) were used to get the radial velocities of primary and secondary components. Both velocities of the primary and secondary stars were calculated with the BF method while only primary velocities were determined with the CCF. Using new radial velocity curves, the maximum radial velocities of the primary and secondary stars were obtained as $K_1=90.1km/s\;and\;K_2=196.6km/s$, respectively. New absolute dimension of BX And was deduced with the combination of our spectroscopic solution with the photometric one of Bell et al. (1990).

• Journal of the Korean earth science society
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• v.43 no.1
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• pp.1-22
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• 2022

We provide a detailed description of the installation and operation of a remote spectroscopic meteor observation system at Unjangsan optical astronomy observatory. Three light-sensitive charge-coupled device cameras were installed, and two cameras had a diffraction grating attached to the front of the lens. Station employ sensitive "Watec-902H2" cameras in combination with f/1.2 lenses were installed in November 2019. Diffraction gratings for spectral observations were used at 500 l/mm. Observations were conducted from November 2019 to June 2020. We employed the SonotaCo UFO software suite for meteor detection. Subsequently, meteor spectra were analyzed using field-tested RSpec software. To analyze the observation images, astronomical calibration and photometric calibration were performed, and the chemical elements of the meteor were determined. The study results are presented along with the system setup installation and operation experience. Brief information regarding the origin of the meteor was also provided based on the results.