• 천문학회보
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• 제35권2호
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• pp.79.2-79.2
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• 2010

We present the results of simultaneous observations of SiO v=1, 2, J=1-0, $^{29}SiO$ v=0, J=1-0, and $H_2O$ $6_{16}-5_{23}$ maser lines performed with the KVN Yonsei 21 m radio telescope from 2009 Nov. to 2010 Jan (ApJ, 719, 126, 2010). We searched for these masers in 47 symbiotic stars and detected maser emission from 21 stars, giving the first time detection from 19 stars. Both SiO and $H_2O$ masers were detected from seven stars of which six stars are D-type symbiotic and one is an S-type star, WRAY 15-1470. In the SiO maser emission, the $^{28}SiO$ v=1 maser was detected from 10 stars, while the v=2 maser detected from 15 stars. In particular, the $^{28}SiO$ v=2 maser emission without the v=1 maser detection was detected from nine stars with its detection rate of 60 %, which is much higher than that of isolated Miras/red giants. The $^{29}SiO$ v=0 maser emission was also detected from two stars, H 2-38 and BF Cyg, together with the $^{28}SiO$ v=2 maser. We conclude that these different observational results between isolated Miras/red giants and symbiotic stars may be related with the presence of hot companions in a symbiotic binary system.

• 천문학회지
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• 제15권2호
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• pp.49-58
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• 1982

The UBVRIHKL magnitudes on Johnson system and space motions of M dwarf stars have been collected. This sample of M stars have been distinguished on a purely kinematical basis; the one with e<0.15, young disk population, with 0.150.3 halo population. On the color-color diagrams and the color excess-orbital eccentricity diagrams, there is no distinction between the old disk stars and the young disk stars. However (I-H) color could be used to distinguish halo stars from young and old disk stars and the color excesses, ${\Delta}(U-B),\;{\Delta}(B-V),\;{\Delta}(V-R),\;{\Delta}(H-K),\;{\Delta}(K-L),\;and\;{\Delta}(B-R)$ can be used as abundance indicators only for the halo stars. But these color excesses which are measures of blue excesses, are positive for the halo stars with smaller eccentricities and become negative for those with larger eccentricities.

• Journal of Astronomy and Space Sciences
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• 제37권3호
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• pp.157-163
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• 2020

High resolution spectroscopic observation of V1719 Cyg were made at 1.8 meter telescope of Bohyunsan Optical Astronomy observatory in Korea. Spectral resolving power was R=45,000, signal to noise ratio S/N>100. The abundances of 28 chemical elements from carbon to dysprosium were found with the spectrum synthesis method. The abundances of oxygen, titanium, vanadium and elements with Z>30 are overabundant by 0.2-0.9 dex with respect to the solar values. Correlations of derived abundances with condensation temperatures and second ionization potentials of these elements are discussed. The possible influence of accretion from interstellar environment is not so strong as for ρ Pup and other stars with similar temperatures. The signs of accretion are absent. The comparison of chemical composition with solar system r- & s-process abundance patterns shows the enhancement of the photosphere by s-process elements.

• 천문학회지
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• 제49권6호
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• pp.295-306
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• 2016

We present the results of BV time-series photometry of the globular cluster NGC 288. Observations were carried out to search for variable stars using the Korea Microlensing Telescope Network (KMTNet) 1.6-m telescopes and a 4k pre-science CCD camera during a test observation from August to December, 2014. We found a new SX Phe star and confirmed twelve previously known variable stars in NGC 288. For the semi-regular variable star V1, we newly determined a period of 37.3 days from light curves spanning 137 days. The light-curve solution of the eclipsing binary V10 indicates that the system is probably a detached system. The pulsation properties of nine SX Phe stars were examined by applying multiple frequency analysis to their light curves. We derived a new Period-Luminosity (P-L) relation, ${\langle}M_V{\rangle}=-2.476({\pm}0.300){\log}P-0.354({\pm}0.385)$, from six SX Phe stars showing the fundamental mode. Additionally, the period ratios of three SX Phe stars that probably have a double-radial mode were investigated; $P_{FO}/P_F=0.779$ for V5, $P_{TO}/P_{FO}=0.685$ for V9, $P_{SO}/P_{FO}=0.811$ for V11. This paper is the first contribution in a series assessing the detections and properties of variable stars in six southern globular clusters with the KMTNet system.

• 천문학회지
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• 제42권6호
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• pp.161-174
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• 2009

Observation of standard stars is of crucial importance in stellar photometry. We have studied the standard transformation relations of the UBV RI CCD photometric system at the Maidanak Astronomical Observatory in Uzbekistan. All observations were made with the AZT-22 1.5m telescope, SITe 2k CCD or Fairchild 486 CCD, and standard Bessell UBV RI filters from 2003 August to 2007 September. We observed many standard stars around the celestial equator observed by SAAO astronomers. The atmospheric extinction coefficients, photometric zero points, and time variation of photometric zero points of each night were determined. Secondary extinction coefficients and photometric zero points were very stable, while primary extinction coefficients showed a distinct seasonal variation. We also determined the transformation coefficients for each filter. For B, V, R, and I filters, the transformation to the SAAO standard system could be achieved with a straight line or a combination of two straight lines. However, in the case of the U filter and Fairchild 486 CCD combination, a significant non-linear correction term - related to the size of Balmer jump or the strength of the Balmer lines - of up to 0:08 mags was required. We found that our data matched well the SAAO photometry in V, B - V, V - I, and R - I. But in U - B, the difference in zero point was about 3.6 mmag and the scatter was about 0.02 mag. We attribute the relatively large scatter in U -B to the larger error in U of the SAAO photometry. We confirm the mostly small differences between the SAAO standard UBV RI system and the Landolt standard system. We also attempted to interpret the seasonal variation of the atmospheric extinction coefficients in the context of scattering sources in the earth's atmosphere.

• Journal of Astronomy and Space Sciences
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• 제26권2호
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• pp.157-170
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• 2009

BVRI 표준성 52개를 충북대학교 천문대에서 1-m 망원경과 2K CCD 카메라로 2008년 9-12월 기간에 10일 밤 관측하여 1,322개의 CCD 영상을 얻었다. 우리가 사용한 측광계 bvr과 Johnson-Cousins의 측광계 BVR과 상호 관계를 V = v - 0.0303(B - V) + 0.0466 B - V = 1.3475(b - v) - 0.0251 V - R = 1.0641(v - r) - 0.0125와 같이 구하였다. 이 식을 이용하여 197개 별들의 V, B-V, V-R를 얻었다.

• 천문학회지
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• 제10권1호
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• pp.3-12
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• 1977

$Str\ddot{o}mgren$-system colors for 23 OV stars compiled by Crawford have been compared with colors calculated by Mihalas from non-LTE model atmospheres. In this way, effective temperatures of these stars have been determined and plotted against spectral type, $c_1$ (u-b), (b-y), (U-B), and (B-V). Within the accuracy of the observations, effective temperatures derived from the photometry for these 23 main-sequence stars are found to be in good agreement with Contiis spectroscopical temperatures.

• 한국측량학회지
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• 제23권1호
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• pp.69-76
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• 2005

본 연구의 목적은 INCA2 카메라와 V-STARS 시스템으로 구성된 산업사진측량 시스템을 이용하여 현장 산업측정 조건에서 강박스거더의 측정을 실시하고, 그 측정 정확도를 평가하는데 있다. 실험을 위하여 코드타겟, 테이프타겟, 에지타겟 및 타겟어뎁터를 이용하였으며, 강박스 거더 부재면과 면사이의 거리, 부재와 리브간의 거리, 가조립을 위한 볼트구멍의 정확한 위치 및 부재면과 면 사이의 교차 각도 등을 측정 대상으로 하였다. 실험결과 본 연구에서 제안한 산업사진측량 기법으로 교량용 강박스 거더를 매우 정확하고, 신속하게 측정할 수 있었다.

• 천문학회지
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• 제43권5호
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• pp.153-159
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• 2010

Color excesses of classical Cepheids in the uvby color system are estimated for the calibration stars with distances from the literature that are measured independently. Intrinsic photometric indices for these stars are calculated and a calibrated empirical relation between (b - y)$_0$, period, [$c_1$], and [$m_1$] is derived through a linear fit. This relation is used to determine color excesses E(b-y) for 59 Cepheids. We also examine the period-color [log P : (b - y)$_0$] relation, and find no signs of nonlinearity. We estimate the effective temperature and surface gravity of several Cepheids using both Kurucz and MARCS/SSG grids for [Fe=H]=0.0. We confirm that both temperature and surface gravity are higher, by about 150K and 0.4 respectively, when the MARCS/SSG atmospheric grids are used.

• Journal of Astronomy and Space Sciences
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• 제25권2호
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• pp.87-100
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• 2008

소백산 천문대의 61cm 망원경에 부착된 bvri CCD 측광 시스템으로 근접쌍성 V523 Cas를 2003년 1월에 4일 밤을 관측하여 792점의 CCD 영상을 얻었다. 이 영상 내에 있는 17개의 BVRI 표준성을 이용하여 소백산 천문대의 bvri 측광계와 Johnson-Cousins의 BVRI 측광계 사이의 변환 관계를 V=v-0.0689(B-V)+0.0063, B-V=1.3197(b-v)-0.1733, V-R=0.9210(v-r)-0.1309, R-I=0.8892(r-i)-0.1055와 같이 구하였다. 이 식을 이용하여 근접쌍성 V523 Cas 근처에 있는 57개 별들의 표준 V등급과 색지수(B-V, V-R, R-I)를 결정하였다.