• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.28.2-28.2
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• 2011

To search for and study the nature of the long-periodic variations of massive stars, we have been carrying out a precise radial velocity (RV) survey for supergiants. Here, we present high-resolution RV measurements of ${\alpha}$ Per which lies near the Cepheid instability strip from November 2005 to February 2011 using the fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) at Bohyunsan Optical Astronomy Observatory (BOAO). The orbital solution yields a period of 129 days, a 2K amplitude of 80 m/s, and an eccentricity of 0.1. Assuming a possible stellar mass of 7.3 $M{\bigodot}$, we estimate the minimum mass for the planetary companion to be 7.5 MJup with the orbital semi-major axis of 0.97 AU. We do not find the correlation between RV variations and chromospheric activity indicator (Ca II H & K region). The Hipparcos photometry and bisector velocity span (BVS) do not show any obvious correlations with RV variations. These analyses suggest that ${\alpha}$ Per is a pulsating supergiant that hosts an exoplanet. If the 129 days variations of ${\alpha}$ Per do not come from an exoplanet but Cepheid-like pulsations, the theoretical boundary of the Cepheid instability strip may need to be extended to the bluer side.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.107.2-107.2
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• 2012

The purpose of the present study is to search for and study the origin of planetary companion by a precise radial velocity (RV) survey for K dwarfs. The high-resolution spectroscopy of the fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) at Bohyunsan Optical Astronomy Observatory (BOAO) is used from September 2008 to June 2012. We report the detection of two new exoplanets in orbit around HD 208527, and HD 220074 with exhibiting a periodic variation of 875.5 and 672.1 days. The examinations of surface inhomogeneous are no related to the RV variations and Keplerian motion is the most likely explanation, which suggests that the RV variations arise from an orbital motion under the influence of planetary companion. We obtain the minimum masses for the exoplanets of 11.5 and 11.1 MJup with an orbital semi-major axis of 2.3 and 1.6 AU and an eccentricity of 0.08 and 0.14, respectively. From the literatures and our estimations of stellar parameters, the luminosity class of HD 208527 is changed K dwarf to K giant and the spectral type of HD 220074 is confirmed M giant rather than K dwarf. HD 220074 is the first M giant star harboring a planetary companion.

• Journal of the Korean earth science society
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• v.33 no.7
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• pp.608-617
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• 2012

The symbiotic nova Z Andromedae (And) was investigated, using the high dispersion spectra of spectral resolution, ${\Delta}{\lambda}{\sim}-0.1{\AA}$. The spectral observations were done with (1) the Hamilton Echelle Spectrograph (HES) and the high resolution spectra (exposures=1800s and 3600s) were obtained at Lick Observatory in 2001 August $30^{th}$ (phase ${\Phi}$=0.77), and 2002 August $12^{th}$ (phase ${\Phi}$=0.22), (2) with the Bohyunsan Echelle Spectrograph (BOES) at Bohyunsan Optical Astronomy Observatory and the high resolution spectra (exposure=1200s) were secured in 2009 October $21^{st}$ (phase ${\Phi}$=0.70). From both the HES and BOES spectral data in the $3600{\AA}-9500{\AA}$ wavelengths, we extracted the emission lines of HI, HeI, and HeII, which have been decomposed into double or triple Gaussian components for 3 consecutive phases. The emission zones responsible for these components appear to be closely related with the orbital motion of a white dwarf or a giant star. The presence of the Raman scattering $H{\alpha}$ broad wing feature and the kinematic characteristics of the line profile observed in each phase imply that the Z And emission lines are mostly from two Lagrangian points, $L_1$ and $L_2$, and the accretion disk around the white dwarf star. The Z And was most active in 2009 and 2001 during the outburst phase, while it remained quiescent in 2002 in spite of the complex line profiles.

• Journal of Astronomy and Space Sciences
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• v.22 no.4
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• pp.353-362
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• 2005

We performed a new high-resolution spectroscopy of AG Vir for 4 nights from 25 March 2004 using the BOES (Bohyunsan Optical Echelle Spectrograph) attached to the 1.8-m reflector at Bohyunsan Optical Astronomy Observatory, and obtained a total of 59 spectra where all orbital phases are covered. To get the radial velocities of the binary system, both method of the CCF (Cross-Co..elation Function)and the BF (Broadening Function) were applied to the analysis of all the observed spectra. From these, the CCF could calculate the radial velocities of the primary star alone, while the BF could determine those of the primary and the secondary components. New absolute dimensions were deduced with the combination of our spectroscopic orbital elements ($K_1=90.5km/s$와 $K_2=258.8$) and the photometric solutions of Bell, Rainger, & Hilditch (1990): $A_1,=1.99M_\bigodot,\;M_2=0.62M_\bigodot,\;R_1=2.21R_\bigodot,\;R_2=1.36R_\bigodot,\;L_1=13.17L_\bigodot,\;and\;L_2=3.47L_\bigodot$. Our absolute parameters are larger and brighter than those derived from Bell, Rainger, & Hilditch (1990). We re-analyzed all the previous radial-velocity curves of AG Vir and, as a result, can see that its system velocity scatters largely up to ${\pm}8km/s$. However, we, at present, cannot determine this as the light-time effect due to the third body, which was suggested as a cause of the orbital period changes by Qian (2001).

• Publications of The Korean Astronomical Society
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• v.16 no.1
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• pp.25-29
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• 2001

We obtained three-color composite. images of 78 celestial objects most of which are listed in Messier catalogue. In order to make color images, 118 raw image sets were taken with B, V, R, I and H-alpha filters. We used the 2k CCD camera attached to the 1.8 m telescope of Bohyunsan Optical Astronomy Observatory. These composite images are to be used for educational purposes or public releases. The images are presented on the website, http://www.boao.re.kr/-ybjeon/boao_images.htrnl.

• Publications of The Korean Astronomical Society
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• v.20 no.1 s.24
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• pp.43-48
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• 2005

We present a high resolution spectrum of PU Vul observed at Bohyunsan Optical Astronomy Observatory (BOAO) on April 9, 2004. Permitted emission and nebular lines of PU Vul had been significantly changed compared to all spectra observed since its eruption in 1979. Therefore all new lines should be re-identified and were done so. We do-convoluted a $H{\beta}$ line into several emission components with Gaussian functions. Then we carefully discussed the geometrical feature of PU Vul in April 2004.

• Publications of The Korean Astronomical Society
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• v.11 no.1
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• pp.243-250
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• 1996

Data acquisition system mounted on the Solar Flare Telescope at Bohyunsan Optical Astronomy Observatory is briefly described. The system is made up with CCD cameras, an image processor, a PCI-type PC and a SUN workstation. The image processor, MVC 150/40 comprises a variable scan acquisition module, an image manager and a binary correlator computational module. A typical polarization image of a sunspot is presented to demonstrate performance of the system.

• Publications of The Korean Astronomical Society
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• v.21 no.2
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• pp.35-42
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• 2006

We report a high resolution spectrum of AG Pegasi observed at Bohyunsan Optical Astronomy Observatory (BOAO) on October 2, 2004. Some of permitted emission lines, for example H I, He I, He II, Fe II and Ti II were observed in the spectrum of AG Pegasi in 2004. Lines presented in the longer wavelength region than $6500{\AA}$ are identified. And radial velocities for each element are measured. Then we carefully discuss the geometrical feature of AG Pegasi in October 2004.

• Current Optics and Photonics
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• v.6 no.5
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• pp.445-452
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• 2022

We developed an adaptive optics test bench using an optical simulator and two rotating phase plates that mimicked the atmospheric turbulence at Bohyunsan Observatory. The observatory was reported to have a Fried parameter with a mean value of 85 mm and standard deviation of 13 mm, often expressed as 85 ± 13 mm. First, we fabricated several phase plates to generate realistic atmospheric-like turbulence. Then, we selected a pair from among the fabricated phase plates to emulate the atmospheric turbulence at the site. The result was 83 ± 11 mm. To address dynamic behavior, we emulated the atmospheric disturbance produced by a wind flow of 8.3 m/s by controlling the rotational speed of the phase plates. Finally, we investigated how closely the atmospheric disturbance simulation emulated reality with an investigation of the measurements on the optical table. The verification confirmed that the simulator showed a Fried parameter of 87 ± 15 mm as designed, but a little slower wind velocity (7.5 ± 2.5 m/s) than expected. This was because of the nonlinear motion of the phase plates. In conclusion, we successfully mimicked the atmospheric disturbance of Bohyunsan Observatory with an error of less than 10% in terms of Fried parameter and wind velocity.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.45.2-46
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• 2021

The Hayabusa 2 mission target asteroid (162173) Ryugu is a near-Earth, carbonaceous (C-type) asteroid. Before the arrival, this asteroid is expected to be covered with mm- to cm- sized grains through the thermal infrared observations [1]. These grains are widely understood to be formed by past impacts with other celestial bodies and fractures induced by thermal fatigue [2]. However, the close-up images by the MASCOT lander showed lumpy boulders but no abundant fine grains [3]. Morota et al. suggested that there would be submillimeter particles on the top of these boulders but not resolved by Hayabusa 2's onboard instruments [4]. Hence, we conducted polarimetry of Ryugu to investigate microscopic grain sizes on its surface. Polarimetry is a powerful tool to estimate physical properties such as albedo and grain size. Especially, it is known that the maximum polarization degree (Pmax) and the geometric albedo (pV) show an empirical relationship depending on surface grain sizes [5]. We observed Ryugu from UT 2020 November 30 to December 10 at large phase angles (ranging from 78.5 to 89.7 degrees) to derive Pmax. We modified TRIPOL (Triple Range Imager and POLarimeter, [6]) to attach to the 1.8-m telescope at the Bohyunsan Optical Astronomy Observatory (BOAO). With this instrument, we observed the asteroid and determined linear polarization degrees at the Rc-band filter. We obtained sufficient data sets from 7 nights at this observatory to determine the Pmax value, and collaborated with other observatories in Japan (i.e., Hokkaido University, Higashi-Hiroshima, and Nishi-Harima) to acquire linear polarization degrees of the asteroid from total 24 nights observations with large phase angle coverage (From 28 to 104 degrees). The observational results have been published in Kuroda et al. (2021) [7]. We thus found the dominance of submillimeter particles on the surface of Ryugu from the comparison with other meteorite samples from the campaign observation. In this presentation, we report our activity to modify the TRIPOL for the 1.8-m telescope and the polarimetric performance. We also examine the rotational variability of the polarization degree using the TRIPOL data.