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

• The Bulletin of The Korean Astronomical Society
• /
• v.40 no.1
• /
• pp.52.3-53
• /
• 2015

The GMT-Consortium Large Earth Finder (G-CLEF) is a fiber-fed, optical band high dispersion echelle spectrograph that selected as the first light instrument for the Giant Magellan Telescope (GMT). This G-CLEF has been designed to be a general- purpose echelle spectrograph with the precisional radial velocity (PRV) capability of 10 cm/sec as a goal. The preliminary design review (PDR) was held on April 8 to 10, 2015 and the scientific observations will be started in 2022 with four mirrors installed on GMT. We have been participating in this preliminary design study in flexure control camera (slit monitoring system), calibration lamp sources, dichroic assembly and the fabrication of the proto-Mangin Mirror. We present the design concept on the parts KASI undertaken, introducing the specifications and capabilities of G-CLEF.

• Journal of the Korean earth science society
• /
• v.28 no.7
• /
• pp.847-856
• /
• 2007

The Planetary nebula NGC 6881 displays quadrupole morphology and it also has a jet feature in its image. We investigated the line profiles of the optical region spectral emission lines, using the Hamilton Echelle Spectrograph (HES) at the Lick observatory. The HES data obtained in this study was the radiation coming from the inner region within the diameter of 4 second of arc. Expansion velocity was obtained, based on the strong emission line profiles of e.g. H, Hel, Hell, [OIII], [NII], [ArIII], [SII], and [SIII}, using the IRAF and StarLink/Dipso reduction packages. The HI recombination lines showed one single peak profile, while the He and forbidden strong lines displayed double peaks. The results of this study show that the outflow velocity of gas increases radially outwards due to the central stellar radiation pressure. It was concluded that three central rings appeared in the HST image are the result of a combined structure of bipolar cones (seen in e.g. HI lines) and a ring (seen in He, [SIII] lines) in projection.

• The Bulletin of The Korean Astronomical Society
• /
• v.36 no.1
• /
• pp.49.2-49.2
• /
• 2011

To investigate whether radio galaxies have systematically different accretion disk compared to radio-quiet AGN, we obtained high quality optical spectra for a sample of 22 young radio galaxies, using the KAST Double Spectrograph at the Lick 3-m telescope. Young radio galaxies are particularly useful since the age of the radio phenomena is comparable to that of accretion disk. Based on the optical emission-line diagnostics of narrow line region, which is thought to be photoionized by the nuclear radiation, we constrain the states of the accretion disk. In addition to strong emission lines, i.e., [O I], [O II], [O III], and [Ne III], we use the [Ar III] line to break the degeneracy between the ionization parameter and the SED shape. We find that young radio galaxies show systematically different emission line ratios compared to radio-quiet Type II AGN, suggesting that young radio galaxies probably have the power-law SED without a strong big blue bump. We will present the main results of the emission-line diagnostics.

• The Bulletin of The Korean Astronomical Society
• /
• v.44 no.1
• /
• pp.56.3-56.3
• /
• 2019

We are currently living in the era of the wide field cosmological surveys, either spectroscopic such as Dark Energy Spectrograph Instrument or photometric such as the Dark Energy Survey or the Large Synoptic Survey Telescope. By analyzing the distribution of matter clustering, we can use the growth of structure, in combination with measurements of the expansion of the Universe, to understand dark energy or to test different models of gravity. But we also live in the era of multi-tracer or multi-messenger astrophysics. In particular, during the next decades radio surveys will map the matter distribution at higher redshifts. Like in optical surveys, there are radio imaging surveys such as continuum radio surveys such as the ongoing EMU or spectroscopic by measuring the hydrogen 21cm line. However, we can also use intensity mapping as a low resolution spectroscopic technique in which we use the intensity given by the emission from neutral hydrogen from patches of the sky, at different redshifts. By cross-correlating this maps with galaxy catalogues we can improve our constraints on cosmological parameters and to understand better how neutral hydrogen populates different types of galaxies and haloes. Creating realistic mock intensity mapping catalogues is necessary to optimize the future analysis of data. I will present the mock neutral hydrogen catalogues that we are developing, using the Horizon run 4 simulations, to cross-correlate with mock galaxy catalogues from low redshift surveys and I will show the preliminary results from the first mock catalogues.

• The Bulletin of The Korean Astronomical Society
• /
• v.44 no.1
• /
• pp.36.1-36.1
• /
• 2019

We present the observed relationship between Eddington ratio (${\lambda}Edd$) and optical narrow-emission-line ratio ([NII] ${\lambda}6583/H{\alpha}$) of X-ray-selected unobscured active galactic nuclei (AGN) at 0.6 < z < 1.7 using 27 near-infrared spectra from the Fiber Multi-Object Spectrograph mounted on the Subaru telescope along with 26 additional sources from the literature. We show that the ${\lambda}Edd$ and [NII] ${\lambda}6583/H{\alpha}$ ratio at 0.6 < z < 1.7 exhibits a similar distribution of ${\lambda}Edd$-[NII] ${\lambda}6583/H{\alpha}$ anti-correlation that has been found for local ( = 0.036), hard X-ray selected AGN. The observed anti-correlation suggests that [N II] ${\lambda}6583/H{\alpha}$ optical narrow-line ratio in the AGN host galaxy may carry important information about the accretion state of the central supermassive black hole, suggesting the observational hint of consistent relationship from local to z ~ 1.7. Further study is necessary to determine whether the ${\lambda}Edd$-[N II] ${\lambda}6583/H{\alpha}$ correlation in high-redshift still holds at ${\log}{\lambda}Edd$ < -2 compared to local AGN.

• Publications of The Korean Astronomical Society
• /
• v.22 no.2
• /
• pp.35-41
• /
• 2007

We present the result of radial velocity observation of a W UMa type binary star EX Leo. We observed the star on February 16, 2003, using Long-Slit spectrograph of BOAO(Bohyunsan Optical Astronomical Observatory). Since the spectral lines are broad due to its fast rotation, it is difficult to distinguish two radial velocities from cross correlation function. Instead of cross correlation function, we used broadening function to develop our own code which estimate the radial velocity of the broadened line spectra. With our own code, radial velocities of primary and secondary stars are derived simultaneously. From the radial velocity curve fit, we obtained $K_1=50.24{\pm}8.29km/s$ and $K_2=254.05{\pm}20.984km/s$ respectively.

• The Bulletin of The Korean Astronomical Society
• /
• v.40 no.2
• /
• pp.27.4-28
• /
• 2015

The GMT-Consortium Large Earth Finder (G-CLEF) is an optical band echelle spectrograph that has been selected as the first light instrument for the Giant Magellan Telescope (GMT). G-CLEF is a general purpose high dispersion instrument that is fiber-fed and capable of extremely precise radial velocity measurements. G-CLEF has undergone a preliminary design review in April 2015 and is now entering final design phase and construction. G-CLEF has been designed to measure the mass of Earth-analogue exoplanets and to make critical observations in near-field and high-Z cosmology. We describe the G-CLEF instrument and several key science missions that shaped the development of G-CLEF. First light on the GMT is scheduled for late 2020.

• The Bulletin of The Korean Astronomical Society
• /
• v.42 no.2
• /
• pp.77.3-77.3
• /
• 2017

We present some results of the spectral analysis for Type Ia supernova SN 2011fe in M101, which was discovered by the Palomar Transient Factory on August 24 2011 UT. We performed spectroscopic observations for SN 2011fe at Bohyunsan Optical Astronomy Observatory with the high resolution echelle spectrograph BOES attached to 1.8-m reflector. Spectra of 18 epochs are obtained from September 6 2011 to April 1 2012 UT. Spectral feature variations for several significant lines and explosion mechanism will be discussed.

• Publications of The Korean Astronomical Society
• /
• v.20 no.1 s.24
• /
• pp.117-124
• /
• 2005

We plan to install the polarimetric optics in the AGU(acqusition and guiding unit) of the 1.8 m telescope at the BOAO(Bohyunsan Optical Astronomy Observatory). With this, the spectropolarimetric observations with the resolution of 45,000 and 60,000 in 4,000 to $8,000{\AA}$ ange could be done by the BOES(BOao Echelle Spectrograph). If we use the precision radial velocity measurement capability of the BOES, the accuracy of the magnetic field intensity measurements with this new BOES stokesmeter will be much increased. We present here the design concept of the BOES stokesmeter. Some details on the optics, mechanical parts, fiber parts and the lab test procedures of this stokesmeter are explained.