• Publications of The Korean Astronomical Society
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• v.29 no.3
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• pp.35-44
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• 2014

In ground-based astronomical spectroscopic observations, there are many telluric absorption lines that are laid on the spectra of celestial objects. To study the physical properties of the celestial objects with these contaminated spectra, the telluric lines should be removed. A conventional method for removing the telluric lines is using the standard stellar spectrum as telluric line. In this paper, we introduce a technique to calculate synthetic telluric spectra and use them to remove telluric lines from a spectrum of a celestial object. We used Line-by-Line Radiative Transfer Model (LBLRTM) for calculating a synthetic spectrum and selected Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) model as atmospheric model. We apply our method to some spectra obtained by Bohyunsan Observatory Echelle Spectrograph (BOES) to show that the telluric lines are well removed from the observed spectra by our model within an accuracy of 2% which is close to the 1-sigma rms of the original spectra.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.60.2-60.2
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• 2016

Oscillating Algol-type eclipsing binaries (oEA) are very interesting objects that have three observational features of eclipse, pulsation, and mass transfer. Direct measurement of their masses and radii from the double-lined radial velocity (RV) data and photometric light curves would be the most essential for understanding their evolutionary process and for performing the asteroseismological study. However, only handful oEA stars were studied in detail. To advance this subject, we have been obtaining high-resolution spectra for several oEA stars using Bohyunsan Optical Echelle Spectrograph (BOES). In this presentation, we present our results such as the accurate absolute parameters and evolutionary states for each object, based on the simultaneous analyses of the light and RV curves.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.59.3-59.3
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• 2016

We report the results of search for exoplanets by a precise radial velocity (RV) survey by using the high-resolution spectroscopy of the fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) at Bohyunsan Optical Astronomy Observatory (BOAO). Since 2003, we have conducted a precise RV survey for ~500 stars, including 55 K giants, ~200 G giants, 10 M giants, 40 K dwarfs, and ~200 northern circumpolar stars. We present the detection of around 20 new exoplanets and brown dwarfs.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.83.2-83.2
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• 2014

We present the two high resolution spectra of the symbiotic star V1016 Cygni obtained with the Bohyunsan Optical Echelle Spectrograph in 2003 and 2005, from which we note the existence of the broad emission feature at 4881 ${\AA}$. We propose that this broad feature is formed from Raman scattering of Ne $VII{\lambda}973$ by atomic hydrogen. Thus far, the detection of Raman scattered lines by atomic hydrogen is limited to O $VI{\lambda\lambda}1032$, 1038 and He $II{\lambda\lambda}940$, 972 and 1025. We perform Monte Carlo simulations to fit the Raman scattered Ne $VII{\lambda}4881$ to investigate the basic spectroscopic properties concerning Ne $VII{\lambda}973$.

• 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 $M_{\bigodot}$.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.223.2-223.2
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• 2012

Grating spectrograph observation in near-infrared bands requires wavelength calibrations. We first need to extract order-strips from the echellogram data using flat images, and then to correct the spatial distortions and wavelength scales of the order strips using calibration arc lamps or the telluric OH emission lines. For very high resolution spectrograph using echelle, however, the arc lamps do not have enough emission lines in the order-strips, so we usually use the OH lines for accurate wavelength calibrations in wavelengths shorter than 2.3 microns. In this poster, we present wavelength calibration methods for longer wavelength bands using the telluric absorption lines in early-type stellar spectra and the telluric atmospheric transmission models. This technique will be applied to the data reduction pipeline for the IGRINS.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.69.2-69.2
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• 2011

We present medium resolution spectra in the near-infrared (IR) band 1.4-1.8 microns at a resolving power of R = 5000-10000 of template stars in G, K, and M types with luminosity classes of III observed by the echelle spectrometer, IRCS, at the SUBARU 8.2 m telescope. Identification of lines in the template star spectra has been completed base on the reference of Arcturus spectrum. We measured equivalent width (EW) of the lines, and analyze the trends of EW through the stellar spectral types.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.43.2-43.2
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• 2011

목성 극지방의 분광 관측 자료에는 $H_3+$, $H_2$, 탄화수소 분자들($CH_4,C_2H_2,C_2H_6$)이 방출선의 형태로 나타난다. 이 분자선들은 2 ~ 3 mm에서는 대부분 관측이 이루어졌지만, 7.8 mm 파장대에서는 탄화수소 분자들 중에서 $CH_4$가 hotspot 형태로 관측이 되었다. 본 연구에서는 마우나케아 천문대의 NASA IRTF (InfraRed Telescope Facility) 망원경 중에 중적외선 고분산 분광기 TEXES (Texas Echelon Cross Echelle Spectrograph)를 설치하여 $CH_4$와 함께 처음 발견된 $C_2H_2$의 특성을 분석하였다. 텍사스 주립대학에서 개발한 TEXES는 5 ~ 25 mm의 관측 파장대에서 저분산(R~3,000), 중 분산(R~15,000), 고분산(R~100,000)으로 관측할 수 있다 (Lacy et al., 2002). 본 연구에 사용된 자료는 2009년 5월 29일에 관측되었으며, 파장대는 7.8 mm 이다.

• Bulletin of the Korean Space Science Society
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• 2010.04a
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• pp.32.2-32.2
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• 2010

보현산 천문대 1.8-m 망원경과 고분산 에셀 분광기 BOES(BOao Echelle Spectrograph)를 이용해 관측한 다년간의 공생별 관측자료 중 AG Draconis와 EG Andromedae의 방출선들을 분석하여 그 분광학적 특성을 밝혀내고자 한다. 수소 Balmer 계열 방출선들과 He I $\lambda5875{\AA}$, He I $\lambda6678{\AA}$, He I $\lambda7065{\AA}$, He II $\lambda4686{\AA}$, O VI $\lambda6030{\AA}$, O VI $\lambda7088{\AA}$ 방출선들의 단 장기 변화와 특징을 살펴보며, 그 방출선들 간의 비교를 통해 두 공생별의 특성 변화에 대해 알아본다.

• Structural Engineering and Mechanics
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• v.68 no.6
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• pp.661-675
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• 2018

In this paper, buckling analysis of hybrid functionally graded plates using a novel four variable refined plate theory is presented. In this theory the distribution of transverse shear deformation is parabolic across the thickness of the plate by satisfying the surface conditions. Therefore, it is unnecessary to use a shear correction factor. The variations of properties of the plate through the thickness are according to a symmetric sigmoid law (symmetric S-FGM). The principle virtual works is used herein to extract equilibrium equations. The analytical solution is determined using the Navier method for a simply supported rectangular plate subjected to axial forces. The precision of this theory is verified by comparing it with the various solutions available in the literature.