• 천문학회보
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• 제40권1호
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• pp.61.1-61.1
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• 2015

We performed a monitoring campaign of a Jupiter-Family comet 17P/Holmes, which underwent the dramatic outburst on 23.3 October 2007 at $r_h=2.44AU$, to investigate the secular change in activity and subsequent physical properties of the inner dust coma before and after the 2014 perihelion passage. The monitoring observation was carried out over two years: from May to July 2013, from July to November 2014, and January 2015 with ~weekly cadence. We conducted photometry monitoring in Rc band using four ground-based telescopes, which are the Ishigakijima Astronomical Observatory 105cm telescope, the Okayama Astrophysical Observatory 50cm telescope, the Nishi-Harima Astronomical Observatory 2m telescope, and the T30 51cm i-telescope, respectively. In order to examine the dust production rate, we put a constraint upon the physical distance from the center of the nucleus as rho=2500km and conducted aperture photometry. We found that the average absolute Rc magnitude over the period between July to November 2014 was mR(1,1,0)~12.29, which was approximately 1.5 magnitudes fainter than those of 2013 data. Accordingly, comet 17P/Holmes seemed to become dormant, although a minor eruption was detected on January 26, 2015. In this presentation, we will introduce our ongoing project for 17P/Holmes and discuss why the nucleus becomes dormant within one orbital period.

• Journal of Astronomy and Space Sciences
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• 제22권3호
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• pp.197-210
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• 2005

Results of 7 nights of CCD VR photometry of the intermediate polar 1RXS J062518.2+733433 obtained at the Korean 1.8m telescope are reported. The corrected ephemeris for the orbital minimum is BJD (Orb.min) = 2453023.6159(42)+0.1966431(33) (E-1735). The corrected ephemeris for the spin maximum is BJD (spin max) = 2452893 78477 (10)+0.01374116815 (17) (E-15382) (cycle numbering corresponds to that of Staude et al.2003). The variations of the shape of the individual spin variations are highly correlated in V and R. The phase of the spin maximum is found to be dependent on the orbital phase. The corresponding semi-amplitude of sinusoidal variations of phase is $0.11{\pm}0.03.$ This new phenomenon is explained by the changing viewing conditions of the accreting magnetic white dwarf, and should be checked in further observations this star and for other intermediate polars. To avoid influence of this effect on the analysis of the long-term spin period variations, the runs of at least one orbital period are recommended. Results of time series analysis are presented in tables.

• 천문학회보
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• 제46권2호
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• pp.53.4-54
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• 2021

Although the era of very large telescopes has come, small telescopes still have advantages for fast follow-up and long-term monitoring observation. Intensive monitoring survey of nearby galaxies (IMSNG) aims to understand the nature of the supernovae (SNe) by catching the early light curve from them with the network of small telescopes from 0.4-m to 1.0-m all around the world. To achieve the scientific goals with heterogeneous facilities, three factors are important. First, automatic processes as soon as data is uploaded will increase efficiency and shorten the time. Second, searching for transients is necessary to deal with newly emerged transients for fast follow-up observation. Finally, the Integrated process for different telescopes gives a homogeneous output, which will eventually make connections with the database easy. Here, we introduce the integrated pipeline, 'gppy' based on Python, for more than 10 facilities having various configurations and its performance. Processes consist of image pre-process, photometry, image align, image combine, photometry, and transient search. In the connected database, homogeneous output is summarized and analyzed additionally to filter transient candidates with light curves. This talk will suggest the future work to improve the performance and usability on the other projects, gravitational wave electromagnetic wave counterpart in Korea Observatory (GECKO), and small telescope network of Korea (SOMANGNET).

• 천문학회지
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• 제25권1호
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• pp.23-46
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• 1992

The electrical, mechanical and optical capabilities have been tested of the microdensitometer PDS 1010GMS at the Korea Astronomy Observatory. The highest stage of scan speed 255 csu (conventional speed unit) is measured to be 47 mm/s. At this speed the position is displaced by $4{\mu}m$ to the direction of scanning and the density is underestimated by $0.4{\sim}0.7D$. Standard deviation in the measured density is proportional to $A^{-0.46}$, where A is the area of scan aperture. The accuracy of position repeatability is ${\pm}1{\mu}m$, and that of density repeatability is ${\pm}(0.003{\sim}0.03)D$. Callier coefficient is determined to be 1.37; the semispecular density is directly proportional to the diffuse density up to 3.5D. Because the logarithmic amplifier has a finite response time, the densities measured at high scan speeds are underestimated to the degree that speeds higher than 200 csu are inadequate for making an accurate astronomical photometry. After power is on, an about 5 hour period of warming is required to stabilize the system electrically and mechanically as well. On the basis of this performance test, we have determined the followings as the optimum scan parameters for the astronomical photometry: For the scan aperture $10\;\sim\;20{\mu}m$ is optimal, and for the scan speed. $20\;{\sim}\;50$ csu is appropriate. These parameter values are chosen in such a way that they may keep the density repeatability within ${\pm}0.01D$, the position displacement under $1{\mu}m$, and the density underestimation below 0.1D even in high density regions.

• Journal of Astronomy and Space Sciences
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• 제16권2호
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• pp.241-254
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• 1999

SX Phe형에 속하는 다주기 변광성 BL Camelopardalis (GD428)에 대하여 전하결합소자(CCD)를 사용한 시계열 차등광전측광을 수행하였다. 관측데이터를 최소자승법과 푸리에 분해(Fourier Decom-position) 방법을 사용하여 주기분석을 시도하였는데 이 변광성의 첫 번째 주기는 0.0391일, 두 번째 주기는 0.0317일 값으로 결정되었고 주기비(PI/PO)는 0.81로 이 변광성은 두 개의 진동양식으로 맥동하는 변광성임을 확인할 수 있었다. 이 주기비 값은 다른 SX Phe형 변광성에 대하여 알려진 값 0.78과 차이가 있고 또한 금속함량비와 주기비 사이의 관계에서도 역시 BL Cam은 다른 SX Phe형 변광성과는 상당한 차이를 보여 이 변광성이 모든 SX Phe형 변광성중에서 매우 극단적인 성질을 갖고 있다는 사실을 확인하였다.

• 한국지구과학회지
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• 제41권3호
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• pp.211-221
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• 2020

이 연구는 SDSS DR7의 적색이동(z)<0.05이고, 동시에 R_pet>6 arcsec, 단축과 장축의 비(b/a)>0.6인 외부은하 25,308개를 분류하고, 색 영상을 육안으로 조사하여 고리 모양의 구조를 가진 531개 은하를 선별했다. 이 은하들이 일차적 표본으로 사용되었고, 이 중 90개의 외부고리 은하 후보를 선택했다. 후보 은하의 u, g, r, i, z 영상에 대한 표면 측광으로부터 도출한 특성을 조사하여 최종으로 69개의 외부고리 은하를 결정했다. 외부고리 은하는 국부은하의 0.3%를 차지하는 것으로 나타났으며, 두 개의 환경 인자, 즉, 가장 가까운 은하까지의 투영 거리와 국부 배경 은하 밀도를 이용하여, 외부고리 은하의 환경 특성을 조사했다. 외부고리 은하의 환경이 다른 은하의 경우와 비교하여 눈에 띄는 차이의 결과는 보이지 않았다.

• 한국지구과학회지
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• 제27권6호
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• pp.695-700
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• 2006

변광성 TU UMi의 변광 유형의 분류를 위하여 소백산 천문대 0.6m광학 망원경과 2K CCD 카메라를 이용하여 B, V, I 필터를 이용한 시계열 측광 관측을 수행하였다. 변광성의 분류를 위하여 V 필터와 I 필터로부터 얻은 광도 곡선의 진폭의 비$({\Delta}i/{\Delta}v)$, 색의 변화$({\Delta}(b-v),\;{\Delta}(v-i))$로 부터 TU UMi가 W UMa형 식쌍성임을 확인하였으며, 우리의 관측 자료에서 2개의 극심 시각(UJD 2453848.04456, HJD 2453848.23088)을 구하였고, 새로운 광도 요소(Min I=HJD 2452500.1344+0.37708907${\times}$E)를 결정하였다.

• 한국지구과학회지
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• 제28권4호
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• pp.491-496
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• 2007

소백산 천문대의 0.6m 광학망원경과 2K CCD 카메라를 이용하여 소행성 55 Pandora에 대한 R 필터 시계열 측광관측을 수행하였다. 관측으로부터 소행성의 자전 주기($P=4.^h8168$)와 진폭(${\Delta}R=0.281{\pm}0.001$란 구하였고, Amplitude-Magnitude 방법을 이용하여, 소행성 55 Pandora의 자전축 방향 ${\lambda}_p((^o)=342$, ${\beta}_p(^o)=64$와 세 축의 비는 a/b=1.27, b/c=1.31인 형태로 자전하고 있음을 알아내었다.

• 천문학회지
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• 제28권2호
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• pp.169-175
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• 1995

Deep V I CCD photometry of the Pegasus dwarf irregular galaxy shows that the tip of the red giant branch (RGB) is located at I = $21.15{\pm}0.10$ mag and (V - I) = $1.58{\pm}0.03$. Using the I magnitude of the tip of the RGB (TRGB), the distance modulus of the Pegasus galaxy is estimated to be $(m\;-\;M)_o\;=\;25.13{\pm}0.11$ mag (corresponding to a distance of d = $1060{\pm}50$ kpc). This result is in a good agreement with the recent distance estimate based on the TRGB method by Aparicio [1994, ApJ, 437, L27],$ (m\;-\;M)_o$ = 24.9 (d = 950 kpc). However, our distance estimate is much smaller than that based on the Cepheid variable candidates by Hoessel et al.[1990, AJ, 100, 1151], $(m\;-\;M)_o\;=\;26.22{\pm}0.20$ (d = $1750{\pm}160$ kpc) mag. The color-magnitude diagram illustrates that the Cepheid candidates used by Hoessel et al.are not located in the Cepheid instability strip, but in the upper part of the giant branch. This result shows that the Cepheid candidates studied by Hoessel et al.are probably not Cepheids, but other types of variable stars. Taking the average of our distance estimate and Aparicio's, the distance to the Pegasus galaxy is d= $1000{\pm}80$ kpc. Considering the distance and velocity of the Pegasus galaxy with respect to the center of the Local Group, we conclude that the Pegasus galaxy is probably a member of the Local Group.

• 한국의류학회지
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• 제21권7호
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• pp.1227-1235
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• 1997

The purpose of this study was to classify the somatotype based on the side view and to analyze the characteristics of each somatotype. In order to reduce the burden of stocks and increase clothing fitness, systematic information on typical body sizes and somatotypes is essential. The subjects were 206 unmarried women aged from 19-29. Data were collected through anthropometry and photometry and analyzed by factor analysis, cluster analysis and analysis of variance. As the result of factor analysis for the classification of somatotypes, 8 factors which explain 74.7% of variance were extracted from 35 photometric and 17 anthrometric data. Using factor scores cluster analysis was carried out and the subjects were classified into 4 cluster.Each cluster was classified as bending type, swayback, turning over type and straight type accordding to its position to the relativeplumb line and their side view contour.