• 천문학회지
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• 제49권5호
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• pp.199-208
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• 2016

We present photometric results of the δ Sct star V1162 Ori, which is extensively monitored for a total of 49 nights from mid-December 2014 to early-March 2015. The observations are made with three KMTNet (Korea Microlensing Telescope Network) 1.6 m telescopes installed in Chile, South Africa, and Australia. Multiple frequency analysis is applied to the data and resulted in clear detection of seven frequencies without an alias problem: five known frequencies and two new ones with small amplitudes of 1.2-1.7 mmag. The amplitudes of all but one frequency are significantly different from previous results, confirming the existence of long-term amplitude changes. We examine the variations in pulsation timings of V1162 Ori for about 30 years by using the times of maximum light obtained from our data and collected from the literatures. The O − C (Observed minus Calculated) timing diagram shows a combination of a downward parabolic variation with a period decreasing rate of (1/P)dP/dt = −4.22 × 10⁻⁶ year⁻¹ and a cyclic change with a period of about 2780 days. The most probable explanation for this cyclic variation is the light-travel-time effect caused by an unknown binary companion, which has a minimum mass of 0.69 M_⊙. V1162 Ori is the first δ Sct-type pulsating star of which the observed fast period decrease can be interpreted as an evolutionary effect of a pre-main sequence star, considering its membership of the Orion OB 1c association.

• Journal of Astronomy and Space Sciences
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• 제28권4호
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• pp.333-344
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• 2011

An optical tracking system has advantages for observing geostationary earth orbit (GEO) satellites relatively over other types of observation system. Regular surveying for unidentified space objects with the optical tracking system can be an early warning tool for the safety of five Korean active GEO satellites. Two strategies of positioning on the observed image of Communication, Ocean and Meteorological Satellite 1 are tested and compared. Photometric method has a half root mean square error against streak method. Also eccentricity method for initial orbit determination (IOD) is tested with simulation data and real observation data. Under 10 minutes observation time interval, eccentricity method shows relatively better IOD results than the other time interval. For follow-up observation of unidentified space objects, at least two consecutive observations are needed in 5 minutes to determine orbit for geosynchronous orbit space objects.

• 천문학회보
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• 제40권2호
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• pp.43.2-43.2
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• 2015

The RGB Bayer filter system consists of a mosaic of R, G, and B filters on the grid of the photo sensors which typical commercial DSLR (Digital Single Lens Reflex) cameras and CCD cameras are equipped with. Lot of unique astronomical data obtained using an RGB Bayer filter system are available, including transient objects, e.g. supernovae, variable stars, and solar system bodies. The utilization of such data in scientific research requires that reliable photometric transformation methods are available between the systems. In this work, we develop a series of equations to convert the observed magnitudes in the RGB Bayer filter system (RB, GB, and BB) into the Johnson-Cousins BVR filter system (BJ, VJ, and RC). The new transformation equations derive the calculated magnitudes in the Johnson-Cousins filters (BJcal, VJcal, and RCcal) as functions of RGB magnitudes and colors. The mean differences between the transformed magnitudes and original magnitudes, i.e. the residuals, are (BJ - BJcal) = 0.064 mag, (VJ - VJcal) = 0.041 mag, and (RC - RCcal) = 0.039 mag. The calculated Johnson-Cousins magnitudes from the transformation equations show a good linear correlation with the observed Johnson-Cousins magnitudes.

• 조명전기설비학회논문지
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• 제21권8호
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• pp.10-19
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• 2007

조명시뮬레이션 소프트웨어는 크게 조명기구의 광학설계를 위한 소프트웨어와 조명계획안의 예측 및 평가를 위한 소프트웨어로 구분할 수 있으며, 그 사용이 점차 증가하고 있다. 조명기구의 광학설계를 위한 시뮬레이션 소프트웨어로는 Photopia 2.0이 대표적이며, 조명계획안의 적합성을 판단하기 위한 시뮬레이션 소프트웨어는 Lumen-micro 2000, Relux 2006, Lightscape 3.2와 AGI 32 등이 있다. 이러한 시뮬레이션 소프트웨어는 측정값과 시뮬레이션 결과값, 그리고 소프트웨어별 시뮬레이션 결과값이 상이하게 나오는 경우가 발생한다. 따라서 본 연구는 임의의 조명기구 측정 배광데이터와 Photopia 2.0의 시뮬레이션 배광데이터를 비교하고, 공간의 규모, 배광데이터, 마감재등의 같은 조건하에 Lumen-micro 2000, Relux 2006, Lightscape 3.2와 AGI 32의 시뮬레이션 결과를 비교하여 차이점의 원인에 분석하고자 한다.

• Journal of Astronomy and Space Sciences
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• 제20권2호
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• pp.143-152
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• 2003

식쌍성 극심시각의 체계적인 측광관측을 위하여 충북대학교 교내에 소형 반자동 망원경 관측시스템을 구축하였다. 이 시스템은 Paramount GT-1100s 독일식 마운트와 Celestron 14 광학계, 그리고 SBIG ST-8 CCD 카메라로 구성되었다. 한편, 관측시스템의 제어는 OBSTOOL이라는 소프트웨어에 의하여 이루어지는데, 이는 상용소프트웨어인 The Sky와 MaximDL에서 지원하는 COM(Component Object Model)을 이용하여 망원경과 CCD 카메라를 제어하도록 개발하였다. 이 시스템은 광전관측방법과 유사하게 망원경을 변광성, 비교성, 검토성 등으로 이동시키며 관측을 수행한다. 또한, 효율적인 자료처리를 위하여 작성한 Perl 스크립트로 관측 자료를 날짜별, 관측시야별, 필터별로 분류하고, IRAF소프트웨어를 이용하여 관측 영상의 전처리작업 등을 수행하도록 하였다. 또한, 이 시스템으로 관측한 식쌍성들의 식부근 광도곡선을 제시한다.

• 천문학회지
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• 제54권4호
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• pp.121-128
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• 2021

It has been known that the global asteroseismic parameters as well as the stellar acoustic mode parameters vary with stellar magnetic activity. Some solar-like stars whose variations are thought to be induced by magnetic activity, however, show mode frequencies changing with different magnitude and phase unlike what is expected for the Sun. Therefore, it is of great importance to find out whether expected relations are consistently manifested regardless of the phase of the stellar magnetic cycle, in the sense that observations are apt to cover a part of a complete cycle of stellar magnetic activity unless observations span several decades. Here, we explore whether the observed relations of the global seismic parameters hold good regardless of the phase of the stellar magnetic cycle, even if observations only cover a part of the stellar magnetic cycle. For this purpose, by analyzing photometric Sun-as-a-star data from 1996 to 2019 covering solar cycles 23 and 24, we compare correlations of the global asteroseismic parameters and magnetic proxies for four separate intervals of the solar cycle: solar minima ±2 years, solar minima +4 years, solar maxima ±2 years, and solar maxima +4 years. We have found that the photometric magnetic activity proxy, S_ph, is an effective proxy for the solar magnetic activity regardless of the phase of the solar cycle. The amplitude of the mode envelope correlates negatively with the solar magnetic activity regardless of the phase of the solar cycle. However, relations between the central frequency of the envelope and the envelope width are vulnerable to the phase of the stellar magnetic cycle.

• 천문학회보
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• 제41권1호
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• pp.66.3-66.3
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• 2016

We report preliminary results from our analyses on the star-forming galaxies in the Herschel/SPIRE survey data over the AKARI/NEP-Wide Field. In this work, we utilize a combination of the SPIRE point source catalogue containing ~ 4,800 sources distributed over the wide (5.6 sq. deg) field and the spectroscopic redshift (zSPEC) data for 1790 selected targets obtained by MMT/Hectospec and WIYN/Hydra. Our analyses take advantages of multi-wavelengths photometric data (28 bands at most) covering from u* to $500{\mu}m$ band as well as continuous MIR wavelengths sampling by AKARI and WISE (4 to $25{\mu}m$). Various physical properties such as total infrared luminosity (LTIR), star formation rate (SFR), and luminosity functions (LFs) will be presented.

• 천문학회보
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• 제37권2호
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• pp.100.2-100.2
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• 2012

We performed near-IR imaging polarimetry of the $5{\times}9$ fields (${\sim}39^{\prime}{\times}69^{\prime}$) around 30 Doradus in the Large Magellanic Cloud (LMC), using the InfraRed Survey Facility (IRSF). We obtained polarimetry data in the J, H, and Ks bands using the JHKs-simultaneous imaging polarimeter SIRPOL in 2008 December and 2011 December. With the reliable LMC field data which were selected using a bad-data-rejection algorithm, we measured Stokes parameters of point-like sources to derive the degree of polarization and the polarization position angle. We present physical relationship between the three bands using the photometric and the polarimetric properties of the sources.

• 천문학논총
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• 제18권1호
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• pp.43-49
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• 2003

Korean Astronomical Data Center (KADC, http://kadc.kao.re.kr) in Korea Astronomy Observatory (KAO) has constructed an archive of Bohyunsan Optical Astronomy Observatory (BOAO) 1.8m telescope data. The archive is consisted of photometric (1KCCD, 2KCCD) and spectroscopic data of 400GB amount for the period of 1997 to 2002,and the first web service is made of the data from 1997 to 2001. In the search page, primary search criterion of object name or coordinates is used. Users can also refine the search criteria using parameters such as observation date, observer(s), data type, and/or instrument. The data identified from the search can be uploaded to the FTP site for further downloading in FITS format. This archive is the first DB of astronomical data made in Korea.

• Journal of Astronomy and Space Sciences
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• 제20권4호
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• pp.403-416
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• 2003

There are common features, in both imaging surveys and image processing, between astronomical observations and remote sensing. Handling large amounts of data, in an easy and fast way, has become a common issue. Implementing pipeline software can be a solution to the problem, one which allows the processing of various kinds of data automatically. As a case study, the development of pipeline software for the EIS (European Southern Observatory Imaging Survey) is introduced. The EIS team has been conducting a sky survey to provide candidate targets to the 250 VLTs (Very Large Telescopes) observations. The survey data have been processed in a sequence of five major data corrections and reductions, i.e. preprocessing, flat fielding, photometric and astrometric corrections, source extraction, and coaddition. The processed data are eventually distributed to the users. In order to provide automatic processing of the vast volume of observed data, pipeline software has been developed. Because of the complexity of objects and different characteristic of each process, it was necessary to analyze the whole works of the EIS survey program. The overall tasks of the EIS are identified, and the scheme of the EIS pipeline software is defined. The system structure and the processes are presented, and in-depth flow charts are analyzed. During the analyses, it was revealed that handling the data flow and managing the database are important for the data processing. These analyses may also be applied to many other fields which require image processing.