• 천문학회보
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• 제39권2호
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• pp.63.2-63.2
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• 2014

We observed a bright type Ia Supernovae SN 2014J located in the nearby starburst galaxy M82 using BOES (Bohyunsan Optical Echelle Spectrograph) for eight nights from day -11 (Jan. 22) to day +102 (May. 15) with respect to maximum brightness in B-band. We found the lines formed in the ejecta such as Si ($6300{\AA}$), whose velocity is more than 10,000km/s respect to the host galaxy as well as those formed in the circumstellar material (e.g. Na I D [$5890{\AA}$, $5896{\AA}$], 100km/s) Also, we found other weak iron ($5780{\AA}$, $5797{\AA}$, $6376{\AA}$, $6613{\AA}$, and $7543{\AA}$), carbon ($8059{\AA}$) and other unknown elements. These lines are also thought to have been formed in circumstellar material. We expect that this study will contribute to revelation of the nature of the progenitor stars.

• 천문학논총
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• 제18권1호
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• pp.75-79
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• 2003

The characteristics of the BOES (Bohyunsan Observatory Echelle Spectrograph) CCD camera is presented. In order to get optimum gain and readout noise of the CCD, we examine the variation of the gain and readout noise by changing the value of output drain voltage of the CCD and measuring the gain using transfer curve, which is defined as the plot of variance versus mean exposure level of a homogeneous light onto the CCD surface. The gain and readout noises are optimised to be 0.5e$^-$/ADU and 3e$^-$, which is good for highest signal-to-noise ratio and contrast for the low light level characteristics of the BOES. We also measure the dark count of the CCD by getting five dark images with 3600 seconds exposure time. The mean dark count from median stacked dark images is essentially zero. A table of positions of defected pixels is also presented.

• 천문학회보
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• 제37권1호
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• pp.77.1-77.1
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• 2012

We present high-resolution radial velocity measurements of K2 giant ${\varepsilon}$ CrB from February 2005 to January 2012 using the fiber-fed Bohyunsan Observatory Echelle Spectrograph at Bohyunsan Optical Astronomy Observatory. We find that the RV measurements for ${\varepsilon}$ CrB exhibit a periodic variation of 418 days with a semi-amplitude of 129 m/s. There is no correlation with RV measurements and inhomogeneous surface features by examining chromospheric activity indicator (Ca II H region), the Hipparcos photometry, and bisector velocity span. Thus, Keplerian motion is the most likely explanation, which suggests that the RV variations arise from an orbital motion. Assuming a possible stellar mass of 1.7 $M_{\odot}$, for ${\varepsilon}$ CrB, we obtain a minimum mass for the planetary companion of 6.7 $M_{Jup}$ with an orbital semi-major axis of 1.3 AU, and an eccentricity of 0.11. We support that more massive stars harbor more massive planetary companions in giant hosting planetary companions (Dollinger et al. 2009), as well as, we discuss the frequency of detected planetary companions with the metallicity distribution in giant (Pasquini et al. 2007; Quirrenbach et al. 2011).

• 천문학회보
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• 제37권1호
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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.

• 천문학회보
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• 제42권2호
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• pp.56.4-57
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• 2017

The GMT-Consortium Large Earth Finder (G-CLEF) is the very first light instrument of the Giant Magellan Telescope (GMT) to be commissioned in 2022. The instrument is a fiber feed, optical band echelle spectrograph that is capable of extremely precise radial velocity measurement. Korea Astronomy and Space Science Institute (KASI) has been involved in the development of the G-CLEF as one member of the international consortium consisted of five astronomical institutes including Smithsonian Astrophysical Observatory (SAO), Observatories of the Carnegie Institution of Washington (OCIW). It is scheduled to have KASI side Critical Design Review in December 2017. In this presentation we will report the recent progress on the critical design activities for the G-CLEF Flexure Control Camera (FCC).

• 천문학회지
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• 제53권1호
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• pp.27-34
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• 2020

We report the detection of exoplanet candidates in orbits around HD 60292 and HD 112640 from a radial velocity (RV) survey. The stars exhibit RV variations with periods of 495 ±3 days and 613±6 days, respectively. These detections are part of the Search for Exoplanets around Northern Circumpolar Stars (SENS) survey using the fiber-fed Bohyunsan Observatory Echelle Spectrograph installed at the 1.8-m telescope of the Bohyunsan Optical Astronomy Observatory in Korea. The aim of the survey is to search for planetary or substellar companions. We argue that the periodic RV variations are not related to surface inhomogeneities; rather, Keplerian motions of planetary companions are the most likely interpretation. Assuming stellar masses of 1.7 ± 0.2M_⊙ (HD 60292) and 1.8 ± 0.2M_⊙ (HD 112640), we obtain minimum planetary companion masses of 6.5 ± 1.0M_Jup and 5.0 ± 1.0M_Jup, and periods of 495.4 ± 3.0 days and 613.2 ± 5.8 days, respectively.

• 천문학회보
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• 제35권1호
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• pp.68.2-68.2
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• 2010

We present near-infrared (NIR) spectra of 6 young stellar objects (YSOs) around the supernova remnant G54.1+0.3 obtained with TripleSpec, a slit-based NIR cross-dispersion echelle spectrograph on th 5-m Palomar Hale telescope covering the entire NIR atmospheric window of 1-2.4 micron. These YSOs, whose formation was possibly triggered by the progenitor of G54.1+0.3, show significant mid-infrared (MIR) excess and have been proposed to be late O- and early B-type YSOs based on their spectral energy distribution. Our TripleSpec observations reveal the existence of strong H and He I lines, consistent with the previous interpretation of their spectral types, while the absence of Br-gamma emission line indicates that the YSOs do not have a nearby circumstellar disk. We discuss the relation between these YSOs and G54.1+0.3 based on the TripleSpec data and previous photometric data as well.

• 천문학회보
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• 제35권2호
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• pp.73.1-73.1
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• 2010

Using the spectroscopic data secured with the Hamilton Echelle Spectrograph attached to a 3-m telescope at the Lick Observatory, we derived the expansion velocities from various line profiles in the 3600 $\AA$ to 10,000 $\AA$ based on the full width at half maximum and double peak of the high dispersion line profiles. The symmetrical shapes of the permitted line profiles indicate that the permitted line zone is symmetrical e.g., a spherical shell or bipolar + torus structures, which might be evidence of relatively recent ejection from the central star. Most other stronger forbidden lines might be coming from a main shell which appears as a bilateral symmetrical morphology, seen in HST and other ground-based telescopic images. The overall expansion velocities of this main shell structure that are responsible for most lines, seem to show the Hubble type expansion, i.e., accelerating shell. The faster expansion velocities of the permitted OII, NII, NIII and perhaps CII lines that do not suit to the Hubble type expansion, imply the existence of a somewhat smaller inner shell inside the outer main shell. We conclude that the nebular shell consists of a swiftly expanding inner shell and an outer normal shell excited by a central star of about 55,000K. The former compact zone appears to be responsible for the permitted C, N, and O lines while the latter extended shell appears to be responsible for H, He, and forbidden lines. We present some evidence that NGC 6833 be a member of the Galactic halo.

• 천문학회보
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• 제42권1호
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• pp.42.4-43
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• 2017

We investigate the long-period radial velocity (RV) variations for M giant HD 18438 and K giant HD 158996 using the high-resolution Bohyunsan Observatory Echelle Spectrograph at the 1.8m telescope of Bohyunsan Optical Astronomy Observatory in Korea. These two target stars are important because HD 18438 is the largest star and HD 158996 is the brightest star for exoplantary system candidate so we can understarnd how evolved stars affect planets by researching these stars. We calculated precise RV measurements of 38 and 24 spectra from November 2010 to January 2017 and June 2010 to January 2017, respectively. We dreived the RV variation period for 719.0 days of HD 18438, 775.6 days for HD 158996. We conclude that the RV variation of HD 158996 is caused by planetary companion which has the mass of 14.7 MJup, semi-major axis of 2.2 AU, and eccentricity of 0.27 assuming the stellar mass of $2.34M{\odot}$. On the other hand, the origin of RV variation of HD 18438 with period of 719.0 days is still uncertain. It might be caused by stellar chromospheric activity or planetary companion, so more observations and tests are required.

• 한국지구과학회지
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• 제30권5호
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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.