• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.50.2-50.2
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• 2019

We present the results of high-resolution (R ≥ 30,000) optical and near-infrared spectroscopic monitoring observations of a FU Orionis-type object, 2MASS J06593158-0405277. We have monitored 2MASS J06593158-0405277 with the Bohyunsan Optical Echelle Spectrograph (BOES) and the Immersion GRating INfrared Spectrograph (IGRINS) since December 2014. Various features produced by wind, disk, and outflow/jet were detected. The wind features varied over time and disappeared about a year after the outburst occurred. The double-peaked line profiles were detected in the optical and near-infrared, and the line widths decrease with increasing wavelength. The disk features in the optical spectra are fit well with G2-type or G5-type stellar spectra convolved with a disk rotational profile of about 45 km s^-1, which corresponds to a disk radius of about 71 R_⊙for a central mass of 0.75 M_⊙. Disk features in near-infrared spectra are fit well with a K1-type stellar spectrum convolved with a disk rotational profile of about 35 km s^-1, which corresponds to a disk radius of about 117 R_⊙ for a central mass of 0.75 M_⊙. We also detected [S II] and H2 emission lines, which are rarely found in FUors but are usually found in the earlier stage of young stellar objects. Therefore, we suggest that 2MASS J06593158-0405277 is in the relatively earlier part of Class II stage.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.90-90
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• 2014

The Immersion Grating Infrared Spectrometer (IGRINS) is the first astronomical spectrograph that uses a silicon immersion grating as its dispersive element. IGRINS fully covers the H and K band atmospheric transmission windows in a single exposure. It is a compact high-resolution cross-dispersion spectrometer whose resolving power R is 40,000. An individual volume phase holographic grating serves as a secondary dispersing element for each of the H and K spectrograph arms. On the 2.7m Harlan J. Smith telescope at the McDonald Observatory, the slit size is $1^{{\prime}{\prime}}{\times}15^{{\prime}{\prime}}$. IGRINS has a plate scale of 0.27" pixel-1 on a $2048{\times}2048$ pixel Teledyne Scientific & Imaging HAWAII-2RG detector with a SIDECAR ASIC cryogenic controller. The instrument includes four subsystems; a calibration unit, an input relay optics module, a slit-viewing camera, and nearly identical H and K spectrograph modules. The use of a silicon immersion grating and a compact white pupil design allows the spectrograph collimated beam size to be 25mm, which permits the entire cryogenic system to be contained in a moderately sized ($0.96m{\times}0.6m{\times}0.38m$) rectangular Dewar. The fabrication and assembly of the optical and mechanical components were completed in 2013. From January to July of this year, we completed the system optical alignment and carried out commissioning observations on three runs to improve the efficiency of the instrument software and hardware. We describe the major design characteristics of the instrument including the system requirements and the technical strategy to meet them. We also present the instrumental performance test results derived from the commissioning runs at the McDonald Observatory.

• Publications of The Korean Astronomical Society
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• v.12 no.1
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• pp.167-172
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• 1997

Detailed low spectral resolution observations of the spectrum have been made for three early spectral type standard stars, HR718, HR1544, HR3454, respectively, for the wavelength region 4,300 A to 7,500 A, using the Bohyunsan Optical Astronomy Observatory (BOAO) Middle- Dispersion Spectrograph. These standard stars were chosen from well-known bright northern standard stars. All of the observed long slit spectral data has been reduced and analyzed using the IRAF reduction procedure. The derived extinction coefficients are compared with the other observatory result. The derived value can be used in the determination of flux calibration of BOAO spectroscopic observation. However, until the high quality data are secured from a new series of observation in the blue region and are re-analyzed together, the extinction coefficients below the 4,000 A wavelength remains unknown.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.41.4-42
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• 2015

The Immersion Grating Infrared Spectrograph (IGRINS) is the first of a new generation of infrared instruments with high sensitivity, high spectral resolution, and broad spectral grasp. IGRINS, a joint project of the University of Texas and the Korea Astronomy and Space Science Institute, designed and constructed by a team at UT, KASI, and Kyung Hee University, has been available to the Korean and Texas communities on the McDonald Observatory 2.7m telescope since 2014 September. On this modest-sized telescope, the instrument has 30 times the spectral grasp of CRIRES at the 8m VLT and is only slightly less sensitive. Already, Korean and UT astronomers have produced a raft of new results in star formation studies, investigations of the interstellar medium, and the nature of cool stars. Several programs are under way to detect and study the atmospheres of exoplanets. We will present highlights from the first 6 months of IGRINS operations and look at the future of IR spectroscopy both with IGRINS and with GMTNIRS, a UT/KASI/KHU instrument for the Giant Magellan Telescope.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.67.3-67.3
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• 2015

We present the high-resolution Immersion GRating INfrared Spectrograph (IGRINS) spectra of two Class I sources, IRAS03445+3242 and IRAS04239+2436. Both sources show the evidence of Keplerian disks; the broadened CO overtone (${\Delta}v=2$) transitions in emission and neutral metal lines (Mg I, Fe I, and Al I) in absorption. The thin Keplerian disk with a rotational velocity of ~100 km s-1 and a gas temperature of 5000 K at the innermost annulus can reproduce the CO overtone transitions including the bandhead emission. The outer dusty disk or the envelope needs to fit the narrow absorption features overlaid on the broad emission lines in the CO overtone transitions.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.71.1-71.1
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• 2015

We prensent the near-infrared(NIR) images of the asymmetric circumstellar disk around a T-Tauri star in the ${\rho}$ Ophiuchi star-forming region, and two faint stellar objects around central star. These results were obtainted with the Subaru Telescope with HiCIAO(the High-Contrast Instrument with Adaptive Optics) and IRCS(the InfraRed Camera and Spectrograph). The disk shows center-offset from the star and a strong morphological asymmetry along both the major and minor axis. The physical conditions in the disk is derived from the infrared visibilites results and the complete spectral energy distribution using HOCHUNK3D, Monte-Carlo radiative transfer code. Two companion candidates are separated by 11.6 arcsec(~1450 au at 125 parsec) and 4.34 arcsec(~540 au at 125 parsec). This could be the first case, which imaged both of planetary mass companions and disk around same star. We discuss physical structures of the disk, and probablity that two candidates are real companions.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.71.2-71.2
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• 2015

We present the high-resolution near-infrared spectra of standard stars observed with Immersion Grating Infrared Spectrograph (IGRINS). IGRINS covers the full spectral range of H and K bands simultaneously with a high spectral resolution (R=40,000), revealing many previously undetected and/or unknown lines. In this work, we present preliminary results of spectroscopic diagnostics for stellar physical parameters. Our ultimate goal is to provide a library of near-infrared spectra of standard stars, which covers all spectral types and luminosity classes, with a high-resolution and high signal to noise ratio ($SNR{\geq}200$).

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.72.2-72.2
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• 2015

Wolf-Rayet galaxies, galaxies which show spectral features produced by Wolf-Rayet stars, are thought to be the place of recent massive star formation since the Wolf-Rayet phase covers relatively short timescale in the life of massive O and B type stars. Studying these galaxies provides a unique chance to understand how massive star formation occurs in a galaxy within a short timescale. In this work, we present the intermediate resolution optical spectra of 12 Wolf-Rayet galaxies obtained using longslit spectrograph on Bohyunsan Optical Astronomy Observatory. We derived the emission line ratios for a number of star-forming knots in each Wolf-Rayet galaxy. Star formation properties in these galaxies are discussed.

• Journal of The Korean Astronomical Society
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• v.37 no.5
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• pp.447-454
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• 2004

During the hierarchical formation of large scale structure in the universe, the progressive collapse and merging of dark matter should inevitably drive shocks into the gas, with nonthermal particle acceleration as a natural consequence. Two topics in this regard are discussed, emphasizing what important things nonthermal phenomena may tell us about the structure formation (SF) process itself. 1. Inverse Compton gamma-rays from large scale SF shocks and non-gravitational effects, and the implications for probing the warm-hot intergalactic medium. We utilize a semi-analytic approach based on Monte Carlo merger trees that treats both merger and accretion shocks self-consistently. 2. Production of $^6Li$ by cosmic rays from SF shocks in the early Galaxy, and the implications for probing Galaxy formation and uncertain physics on sub-Galactic scales. Our new observations of metal-poor halo stars with the Subaru High Dispersion Spectrograph are highlighted.

• Journal of The Korean Astronomical Society
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• v.38 no.2
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• pp.81-84
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• 2005

We are undertaking an extra-solar planet search around G-type giant stars by means of Doppler technique using an iodine absorption cell installed to the high dispersion echelle spectrograph for the 188 cm reflector at Okayama Astrophysical Observatory (Okayama Planet Search Program, OPSP). Having detected the first planet candidate (Sato et al. 2003)the search has been proved very promising. Taking advantage of this success, we are trying to develop OPSP to an international collaborative work. We here report the current status of our efforts for establishing such collaborations, namely, those with Chinese and Korean astronomers. We also propose to establish an East-Asian network to search for extra-solar planets around G-type giant stars with the transit detecting technique as well as the Doppler technique, asking other persons/groups to join us to enjoy the planet search.