• 천문학회보
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• 제43권1호
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• pp.64.1-64.1
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• 2018

SNe light curves have been used to understand the expansion history of the universe, and a lot of efforts have gone into understanding the overall shape of the radioactively powered light curve. However, we still have little direct observational evidence for the theorized SN progenitor systems. Recent studies suggest that the light curve of a supernova shortly after its explosion (< 1 day) contains valuable information about its progenitor system and can be used to set a limit on the progenitor size, R*. In order to catch the early light curve of SNe explosion and understand SNe progenitors, we are performing a ~8hr interval monitoring survey of nearby galaxies (d < 50 Mpc) with 1-m class telescopes around the world. Through this survey, we expect to catch the very early precursor emission as faint as R=21 mag (~0.1 Rsun for the progenitor). In this poster, we outline this project, and present a few scientific highlights, such as the early light curve of SN 2015F in NGC 2442.

• 천문학회보
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• 제38권1호
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• pp.32.2-32.2
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• 2013

We examine large-scale environmental effects on the formation and the mass growth of dark matter halos. To facilitate this, we constructed dark matter halo merger trees from a cosmological N-body simulation, which enabled us to trace the merger information and the assembly history of individual halos. In fact, since the massive halos are more likely to be distributed in denser regions than in less dense regions (Mo & White, 1996), the large-scale environment dependence of the properties of halos can be partly originated from the halo mass effect. In order to avoid such contamination, caused by the mass dependence of halo properties, we carefully measured the local overdensity as the indicator of large-scale environment, which was calculated to be as independent of halo mass as possible. Small halos (${\sim}10^{11-12}M_{\odot}$), which usually host isolated single galaxies, show a notable difference on the formation time of galaxies depending on their large-scale environments, which reconfirms halo assembly bias (Gao & White, 2007). Furthermore, we investigate how this environmental effect on small halos is correlated with the mass assembly history of galaxies by using our semi-analytic model. We found that assembly bias in small halos does not have significant effects on the formation time or on the star formation history of galaxies residing in those halos except for the individual stellar mass of galaxies at z = 0. On average, isolated galaxies in high-density regions tend to be slightly more massive than those in low-density regions. Although the observational data from the current galaxy surveys is not yet sufficient for testing this prediction, future galaxy surveys will be able to explore these small galaxies more thoroughly.

• 천문학회지
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• 제54권2호
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• pp.37-47
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• 2021

Reverberation mapping (RM) is an efficient method to investigate the physical sizes of the broad line region (BLR) and dusty torus in an active galactic nucleus (AGN). The Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer (SPHEREx) mission will provide multi-epoch spectroscopic data at optical and near-infrared wavelengths. These data can be used for RM experiments with bright AGNs. We present results of a feasibility test using SPHEREx data in the SPHEREx deep regions for torus RM measurements. We investigate the physical properties of bright AGNs in the SPHEREx deep field. Based on this information, we compute the efficiency of detecting torus time lags in simulated light curves. We demonstrate that, in combination with complementary optical data with a depth of ~ 20 mag in B-band, lags of ≤ 750 days for tori can be measured for more than ~ 200 bright AGNs. If high signal-to-noise ratio photometric data with a depth of ~ 21-22 mag are available, RM measurements are possible for up to ~ 900 objects. When complemented by well-designed early optical observations, SPHEREx can provide a unique dataset for studies of the physical properties of dusty tori in bright AGNs.

• 천문학회보
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• 제38권2호
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• pp.82.1-82.1
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• 2013

The SPICA (SPace Infrared Telescope for Cosmology & Astrophysics) project is a next-generation infrared space telescope optimized for mid- and far-infrared observation with a cryogenically cooled 3m-class telescope. Owing to unprecedented sensitivity and high spatial resolution, the focal plane instruments are expected to perform the confusion-limited observation. The SPICA will challenge to reveal many astronomical key issues from the star-formation history of the universe to the planetary formation. The Korean 5contribution to SPICA as an international collaboration is the development of the near-infrared instrument, FPC (Focal Plane Camera). The Korean consortium for FPC proposed a key system instrument for the purpose of a fine guiding (FPC-G) complementing the AOCS (Attitude and Orbit Control System). The back-up instrument of FPC-G, FPC-S will be responsible for the scientific observations as well. Through the international review process, we have revised the scientific programs and made the feasibility study for the fine guiding system. Here, we report the current status of SPICA/FPC project.

• 한국수학사학회지
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• 제28권3호
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• pp.119-132
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• 2015

This survey is the second part of the history of science of Song and Yuan dynasties and will covers the period from Jin to Yuan. Following the first part, we look at the calendrical astronomy, mathematics and medicine. In this survey we again follow Yabuuchi's work on the history of science of Song and Yuan period and Du Shiran's work on the history of science of China. We start from the sciences and mathematics of Jin which inherited those of Northern Song and see how they influenced the whole China including Yuan and Southern Song. As a conclusion the tendency to practical usages in the Southern Song as well as the suppression of Han people in Yuan prevented developments of theoretical sciences in Yuan and Ming later.

• 한국실내디자인학회논문집
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• 제15권1호
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• pp.131-138
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• 2006

This paper compares presentation methods which are characteristic among museums of natural history in Korea. The different medium for exhibitions are divided into Specimen, Model or Panel Type Displays, Video Presentations, Sound, and Tactile Exhibits, and further classified as Fixed (A Type), Observable (B Type), or Performance Art (C Type) Displays. The museums we studied were the Seodaemun Museum of Natural History, Ewha Womans University Museum of Natural History, Seoul National Science Museum, Gyeryongsan Natural History Museum, the National Science Museum, Mokpo Natural History Museum, and the JejuDo Folklore and Natural History Museum. A study of these museums' approaches to display composition, and exhibition methods according to their exhibit types and contents, revealed the following results: The museums of natural history rely more on Fixed type displays to show information, with appropriate uses of the Observable and the Performance Art type exhibitions. Better utilization of appropriate medium is desired for display contents of Astronomy Space Earth, Minerals Rocks Geology, Animals, Plants, Insects, Prehistoric Organisms Environment, and Anthropology.

• 한국수학사학회지
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• 제28권1호
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• pp.1-14
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• 2015

This survey is the first part of the history of science of Song and Yuan dynasties and covers the period starting from Song to Jin. The major science in the Song period consists of calendrical astronomy, mathematics and medicine, and mathematics is also related to water supply technology. In this survey we follow Yabuuchi's work on the history of science of Song and Yuan period and Du Shiran's work on the history of science of China. We will try first to see how academic science flourished in the Northern Song, what caused the public science to prevail in the Southern Song, and then how the academic trend continued in Jin. We will continue to cover the Jin-Yuan period in the ensuing survey.

• Journal of Astronomy and Space Sciences
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• 제21권1호
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• pp.39-72
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• 2004

《삼국사기》, 《고려사》, 《조선왕조실록》, 《승정원일기》 등 정통 한국 사서 원전에 수록되어 있는 천문관측 자료에서 별똥비와 별똥 소나기 기록을 검색하여 천문학적인 검토를 거쳐 그 목록을 작성하였다. 한국 사서에 나오는 별똥비 기록은 현재 국제 학계에 1958년 Imoto와 Hasegawa가 영문으로 발표한 논문이 표준이 되고 있는데, 이 문헌은 주로 1917년에 조선총독부에서 주관한 연구과제의 일환으로 일본인 관구리길가 작성한 보고서를 바탕으로 하고 있다. 그가 만든 목록은 날짜나 원전 인용 상의 오류를 상당히 포함하고 있으므로 본 연구에서는 한국의 정사서 원전을 검색하여 철저한 고증을 거쳐 수정되고 확장된 별똥비 및 별똥 소나기 목록을 작성하였다. 그 결과 지난 2천년 동안 한국의 역사서에는 별똥 소나기가 25번, 센별똥비가 4번, 보통 별똥비가 5번 기록되어 있었다. 그 가운데 일부는 사자자리 별똥비, 페르세우스 별똥비, 핼리혜성의 의해 생기는 물병자리-/sub n/ 별똥비와 오리온자리 별똥비 등에 속한 것으로 보이는 것이 있었으나, 상당히 많은 기록들은 이에 속하지 않았다. 본 연구에서 제시한 목록은 추후 많은 천체물리학적 연구에 유용할 것이다.

• 천문학회보
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• 제36권2호
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• pp.63.2-63.2
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• 2011

We describe the Infrared Medium-deep Survey (IMS), a survey of quasars in the early universe beyond z=5. IMS uses multi-wavelength archival data such as SDSS, CFHT-LS, UKIDSS, and SWIRE, which provide deep images over wide area enough for searching of high redshift bright quasars. In addition, we are carrying out J-band imaging survey with the depth of 23AB at UKIRT for up to 200 $deg^2$, of which 50 $deg^2$ is covered so far. For the quasar candidates at z~5.5, we are making observations with custom-made filters, which are more efficient to make robust quasar candidate samples in this redshift range. Because of the deeper survey depth and the unique methods, our IMS can provide a large number of high redshift quasars comparing with ongoing high redshift bright quasar survey. The high redshift quasars we confirm will give us with clues of the growth of super massive black holes and the metal enrichment history in the early universe.

• Journal of Astronomy and Space Sciences
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• 제23권1호
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• pp.55-70
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• 2006

한국의 역사서에 속에는 혜성을 관측한 기록이 많이 있다. 우리는 그 가운데 조선 현종 5년 1664년 겨울에 나타난 혜성을 관측한 기록을 <성변측후단자>, <천변등록>, <승정원일기>, <조선왕조실록>에서 수집 정리하였다. 우리는 올버스(Olbers)의 방법을 사용하여 혜성의 예비 궤도 요소를 구하고, 그것을 이전의 연구들과 비교하였다 올버스의 방법에서는 혜성 궤도의 이심율 e=1인 포물선 케도로 가정한다 관측 자료를 사용하여 궤도를 계산한 결과, 근일점 거리 (perifocal distance) $q=1.07\pm0.008AU$, 근일점 통과 시간 $T=2329165.50\pm0.72$일, 승교점과 근일점의 이각(argument of the perifocus) $\omega=318^{\circ}.2\pm2^{\circ}.29$, 승교점 경도(longitude of the ascending node) $\Omega=85^{\circ}.23\pm2^{\circ}53(J1665)$, 궤도 경사(inclination) $i=160^{\circ}.28\pm1^{|circ}.56$를 얻었다.