• 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 $VII{\lambda}973$.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.71.2-71.2
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• 2014

For better understanding of the physics of pores, we have investigated horizontal and vertical motions of plasma in a pore obtained on 2013 August 24 by using high time and spatial resolution data from the Fast Imaging Solar Spectrograph (FISS) of the 1.6 meter New Solar Telescope (NST). We infer the LOS velocity by applying the bisector method to the wings of Ca II 8542 ${\AA}$ profile, and inspect oscillations of the intensity and the LOS velocity in the pore. In this presentation, we discuss the physical implications of our results in view of a connection between LOS and horizontal plasma flows in a concentrated magnetic flux.

• 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 $M_{\bigodot}$.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.375-379
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• 2015

Planetary nebula in elliptical galaxies pose a problem in dark matter theory. Using data from the Planetary Nebula Spectrograph (PN. S), Romanowsky et al. (2003) reported that less dark matter than expected was found within 5 to 6 effective radii of three elliptical galaxies. We attempt to explain similar observations of elliptical galaxies with MOdified Newtonian Dynamics (MOND). We collect 16 elliptical galaxies with planetary nebulae from the public web data of PN. S. We investigate the dynamical behavior by analyzing the line-of-sight velocity dispersion in the framework of MOND.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.757-759
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• 2015

I use a common educational spectrographic device (SV2100R) in order to obtain astronomical spectra after inventing a new adaptor for telescopes. Experimental classes and learning projects in schools and public outreach are well established regarding imaging and photometry observations. However, experiments using astronomical spectrographs are rather hard to find because the procedures of spectral extraction and wavelength calibration is less convenient. SV2100R is a 1D CCD array and thus has the advantage of not requiring spectral extraction. In addition, basic wavelength calibration is preformed by the the provided software. It was adapted to a 12-inch reflecting telescope in the Korea Science Academy of KAIST in Busan and a spectrum of the bright object, Arcturus, was successfully obtained. This means one can provide educational programs on the topic of astronomical spectra. A few suggested projects are presented.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.88.2-88.2
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• 2012

We present kinematic properties of the narrow-line region in three type-2 QSOs at z~0.35, using 2-D spectra obtained with the VIMOS integral field unit spectrograph at the Very Large Telescope. One of the objects shows a line-of-sight velocity shift of the [OIII] and $H{\beta}$ lines up to 40km/s on a 15 kpc scale, which can be interpreted as either outflow or rotation. The outflow scenario is supported by the presence of blue wings and a radio structure showing lobes in the same direction. Another object features double-peaked emission lines which can be decomposed into two velocity components. Its Hubble Space Telescope image shows two nuclei separated by ~0.2"(~1kpc), implying this may be a binary AGN.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.130.1-130.1
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• 2012

Canceling magnetic features (CMFs) are likely to be a result of magnetic reconnection in the lower atmosphere of the Sun. CMFs are related with chromospheric phenomena such as brightening or jets. In order to observe the fine-scale and highly dynamical structures in the chromospheres, Fast Imaging Solar Spectrograph (FISS) was developed and installed at 1.6 m New Solar Telescope at Big Bear Solar Observatory. Using this FISS data we have studied chromospheric brightenings associated with CMFs. As a result, the chromospheric brightenings related with CMFs have stronger shock waves than one of other regions such as internetwork regions or unipolar magnetic elements

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.48.2-48.2
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• 2011

Using the newly commissioned Fiber-Multi-Object-Spectrograph at the Subaru telescope, we obtained near-IR spectra of a sample of 19 AGNs at 0.6 < z < 2.6, selected from the NOAO Deep Wide-Field Survey (NDWFS) Bootes field, in order to calibrate high-z black hole mass (MBH) estimators. MBHs are generally determined through the kinematics of ionized gas clouds around the black hole assuming virial equilibrium. The velocity profiles of $H{\beta}/H{\alpha}$, MgII and CIV are used to infer the gas kinematics of low-z, mid-z, and high-z quasars, respectively. However, the MBH based on MgII and CIV is not very well calibrated. We compare the $H{\alpha}$ - based MBH estimates from the new FMOS near-IR spectra, with the MgII-based MBH estimates from our existing optical spectra, and investigate the systematic differences.