• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.57.2-57.2
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• 2021

Variability in Young Stellar Objects (YSOs) can be caused by time-dependent accretion rates, geometric changes in the circumstellar disks, the stochastic hydromagnetic interactions between stellar surfaces and inner disk edges, reconnections within the stellar magnetosphere, and hot/cold spots on stellar surfaces. We uncover ~1400 variables from a sample of ~5300 YSOs in nearby low-mass star-forming regions using mid-IR light curves obtained from the 5.5-years NEOWISE All Sky Survey. The mid-IR variability traces a wide range of dynamical, physical, and geometrical phenomenon. We classify six types of YSO variability based on their light curves: secular variability (Linear, Curved, Periodic) and stochastic variability (Burst, Drop, Irregular). YSOs in earlier evolutionary stages have higher fractions of variables at all types and higher amplitudes for the variability. Along with brightness variability, we also find a diverse range of secular color variations, which can be attributed to a competitive interplay between the variable accretion luminosity of the central source and the variable extinction by material associated with the accretion process. We compare the variability of known FUors/EXors and VeLLOs/LLSs, which represent two extreme ends (burst versus quiescent) of the episodic accretion process; FUors/EXors have a higher fraction of variables (65%) than VeLLOs/LLSs (41%). Short-term (few day) and long-term (decades) variability, as well as possible AGB contamination in the YSO catalogues, are also discussed.molecules become more complex by surface chemistry induced directly by high energy photons or by the thermal energy diffused over heated grain surface. Therefore, the ice composition is an

• Journal of Space Technology and Applications
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• v.1 no.2
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• pp.199-216
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• 2021

In 2020, the solar and space environment division at the Korea Space Science Society surveyed the status of data archives in solar physics, magnetosphere, and ionosphere/upper atmosphere in Korea to promote broader utilization of the data and research collaboration. The survey includes ground- and satellite-based instruments and developing models by research institutes and universities in Korea. Based on the survey results, this study reports the status of the ground-based instruments, data products in the ionosphere and upper atmosphere, and documentation of them. The ground-based instruments operated by the Korea Polar Research Institute and Korea Astronomy and Space Science Institute include ionosonde, Fabry-Perot interferometer in Arctic Dasan stations, Antarctic King Sejong/Jang Bogo stations, and an all-sky camera, VHF radar in Korea. We also provide information on total electron content and scintillation observations derived from the Global Navigation Satellite System (GNSS) station networks in Korea. All data are available via the webpage, FTP, or by request. Information on ionospheric data and models is available at http://ksss.or.kr. We hope that this report will increase data accessibility and encourage the research community to engage in the establishment of a new Space Science Data Ecosystem, which supports archiving, searching, analyzing, and sharing the data with diverse communities, including educators, industries, and the public as wells as the research scientist.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.57.2-57.2
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• 2019

The NISS (Near-infrared Imaging Spectrometer for Star formation history) onboard NEXTSat-1 was successfully launched on last December and is now under the operation phase. The capability of both imaging and spectroscopy is a unique function of the NISS. It has realized the imaging spectroscopy (R~20) with a wide field of view of $2{\times}2deg$. in a wide near-infrared range from 0.95 to $2.5{\mu}m$. The major scientific mission is to study the cosmic star formation history in the local and distant universe. It also demonstrated the space technologies related to the infrared spectro-photometry in space. The NISS is performing the imaging spectroscopic survey for local star-forming galaxies, clusters of galaxies, star-forming regions, ecliptic deep fields and so on. As an extension of the NISS, the SPEHREx (Spectro-Photometer for the History of the Universe Epoch of Reionization, and Ices Explorer) was selected as the NASA MIDEX (Medium-class Explorer) mission (PI Institute: Caltech). As an international partner, KASI will participate in the development and the science for SPHEREx. It will perform the first all-sky infrared spectro-photometric survey to probe the origin of our Universe, to explore the origin and evolution of galaxies, and to explore whether planets around other stars could harbor life. Compared to the NISS, the SPHEREx is designed to have a much wider FoV of $3.5{\times}11.3deg$. as well as wider spectral range from 0.75 to $5.0{\mu}m$. Here, we introduce the status of the two space missions.

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.213-216
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• 2012

We have collected dozens of mid-infrared spectra showing UIR bands from diffuse Galactic emitting regions with the AKARI's Infrared Camera (IRC) onboard AKARI, as part of the ISMGN Mission Program. The datasets cover various directions in the inner Galactic Plane ($|l|$ < 70 deg), in the outer Galactic Plane ($|l|$ > 70 deg), and in the off-Plane ($|b|$ > 2 deg). The variations in the UIR band ratios are examined in terms of the radiation environments judged from the far-infrared ($50-170{\mu}m$) spectral energy distribution (SED) made with AKARI/FIS All Sky Survey data at each slit position where mid-IR spectra were obtained. We have found that the band ratios of $6.2{\mu}m/11.2{\mu}m$ and $7.7{\mu}m/11.2{\mu}m$ toward the inner Galaxy are systematically higher than those toward the outer Galaxy and off the Galactic plane. Likely causes of the variations in properties of UIR bands in diffuse emission on a Galactic scale are discussed in this paper.

• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.109-111
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• 2017

We detected bright mid- to far-infrared emission from the helium nova V445 Puppis in the AKARI all-sky survey data taken in 2006. Assuming an optically thin condition, we decomposed the spectral energy distribution (SED) of V445 Puppis in October 2006 by model fitting and found that the SED can be explained by a combination of cold amorphous carbon (125 K and the mass of $4.5^{+6.6}_{-2.7}{\times}10^{-4}M_{\odot}$) and warm amorphous carbon (250 K and the mass of $1.8^{+1.0}_{-0.5}{\times}10^{-5}M_{\odot}$). Assuming that the former is pre-existing dust formed in the past nova outbursts and the latter is newly formed dust in December 2000's nova wind, this result suggests that the amount of dust formed around V445 Puppis in a single outburst is larger than $10^{-5}M_{\odot}$, which is larger than those in any other classical novae ever reported.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.49.2-49.2
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• 2016

The number of discovery of asteroids with peculiar rotational states has recently increased, and hence a novel approach for lightcurve analysis is considered to be critical. In order to investigate objects such as Non-Principal Axis (NPA) rotator, we selected a NPA candidate, (5247) Kryolv as our target considering its Principal Axis Rotation (PAR) code and the visibility in early 2016. The observations of Krylov were made using Korea Microlensing Telescope Network (KMTNet) 1.6 m telescopes installed at the three southern sites with TO (Target of Opportunity) observation mode. We conducted R-band time-series photometry over a total of 51 nights from January to April 2016 with several exposures during each allocated run. The ensemble normalization photometry was employed using the AAVSO Photomtric All-Sky Survey (APASS) catalog for the standardization. We successfully confirmed its NPA spin state based on the deviation from the reduced lightcurve, and thus Krylov is recorded as the first NPA rotator of its kind in the main-belt, with its precession and rotation periods, $P{\varphi}=81.18h$ and $P_{\Psi}=67.17h$, respectively. In this paper, we present the spin direction, the 3D shape model and taxonomy of the newly confirmed NPA asteroid (5247) Krylov.

• Journal of the Korean Society of Clothing and Textiles
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• v.28 no.1
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• pp.172-181
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• 2004

The purpose of this study was to develop functional lab gowns in the view of safety and work efficiency. As the first step of this study, we surveyed on satisfaction rates, preferences and inconvenience items in regard of lab gowns. The data was obtained from 138 graduate students specialized in science and 113 medical students. Respondents answered that the first purpose of wearing lab gown was to protect body from danger. Wearing frequency followed with ‘always’, ‘as possible as’, and then ‘sometimes’. Forty-five percentage of respondents answered that they didn't wear lab gowns often in summer because of hot weather. The contaminated or damaged parts of lab gowns followed with cuffs, abdomen, thigh, lower part, and then chest. Washing frequency followed with ‘once a month’, ‘once per six months’, and then ‘more than once a week’ There were significant differences in normal wearing frequency, wearing frequency by season and washing frequency due to major. There were no significant difference by sex and major in all questions. In regard of the protective capacity of current lab gowns, most respondents answered that ‘It's normal’(60%), ‘It's enough’(21%), so that they didn't show much dissatisfaction. Forty-three percentage of respondents were not satisfied with cuffs. Respondents answered that the cuffs were in danger and inconvenient because of broad cuffs. In regard of color, preference for white were high and followed with ivory, light sky, light green. and then light pink. Materials of current lab gowns were cotton/polyester or polyester 100%. Sixty-eight percentage of respondents were satisfied with that and others were not. The reasons for dissatisfactions were as follows; those materials were not protective to chemicals thoroughly enough. Cotton/polyester materials were heavy. Wearing sensation of polyester 100% was not good.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.147.2-147.2
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• 2011

We have initiated a long-term identification campaign of supernova remnant candidates in X-ray regime. In the short-listed unidentified sources from the ROSAT All Sky Survey, we have chosen the brightest candidate, G308.3-1.4, as our pilot target for a dedicated investigation with Chandra X-ray Observatory. Our observation has revealed an incomplete shell-like X-ray structure which well-correlated with the radio feature. Together with the spectral properties of a shocked heated plasma, we confirm that G308.3-1.4 is indeed a supernova remnant. A bright X-ray point source which locates close to the remnant center is also uncovered in this observation. Its spectral behavior conform with those observed in a rare class of neutron stars. The properties of its optical/infrared counterpart suggests the evidence for a late-type companion star. Interestingly, possible excesses in B-band and H-alpha have been found which indicate this can be an accretion-powered system. With the further support from the putative periodicity of ~1.4 hrs, this source can possibly provide the direct evidence of a binary system survived in a supernova explosion for the first time.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.34.4-35
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• 2009

We have studied the radial g-r color gradients of early-type galaxies in the Sloan Digital Sky Survey (SDSS) DR6 in the redshift range 0.00 < z < 0.06. The color profiles of ~30 per cent of the galaxies in this sample show positive color gradients (centers being bluer). These positive gradient galaxies often show strong $H\beta$ absorption line strengths or emission line ratios that are consistent with star-forming populations. Combining the optical data with Galaxy Evolution Explorer (GALEX) UV photometry, we find that all positive gradient galaxies show blue UV-optical colors. They also exhibit a tendency of having a lower stellar velocity dispersion. Positive gradient galaxies tend to live in lower density regions than negative gradient galaxies and are likely to have a late-type companion galaxy. On the other hand, massive early-type galaxies show negative color gradients. A simplistic population analysis shows that these positive color gradients are visible only for half a billion years after a star burst. Although the effective radius decreases and mean surface brightness increases due to this centrally concentrated star formation, the positions of the positive gradient galaxies on the fundamental plane cannot be reproduced by any amount of recent star formation. Instead it required a lower velocity dispersion.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.47.1-47.1
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• 2018

The NISS (Near-infrared Imaging Spectrometer for Star formation history) onboard NEXTSat-1 have successfully developed by KASI. The capability of both imaging and spectroscopy is a unique function of the NISS. At first, it have realized the low-resolution spectroscopy (R~20) with a wide field of view of $2{\times}2deg$. in a wide near-infrared range from 0.95 to $2.5{\mu}m$. The major scientific mission is to study the cosmic star formation history in local and distant universe. It will also demonstrate the space technologies related to the infrared spectro-photometry in space. Now, the NISS is ready to launch in late 2018. After the launch, the NISS will be operated during 2 years. As an extension of the NISS, the SPEHREx (Spectro-Photometer for the History of the Universe Epoch of Reionization, and Ices Explorer) is the NASA MIDEX (Medium-class Explorer) mission proposed together with KASI (PI Institute: Caltech). It will perform the first all-sky infrared spectro-photometric survey to probe the origin of our Universe, to explore the origin and evolution of galaxies, and to explore whether planets around other stars could harbor life. Compared to the NISS, the SPHEREx is designed to have much more wide FoV of $3.5{\times}11.3deg$. as well as wide spectral range from 0.75 to $5.0{\mu}m$. After passing the first selection process, the SPHEREx is under the Phase-A study. The final selection will be made in the end of 2018. Here, we report the status of the NISS and SPHEREx missions.