• 천문학회지
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• 제28권2호
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• pp.197-208
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• 1995

Real time CCD differential photometry was performed for BT Cnc in Praesepe cluster from February to March, 1994. New 885 differential V magnitudes were obtained for thirteen nights. From the frequency analysis, we have detected two distinct pulsational frequencies of $f_1$=9.7783c/d and $f_2$=7.0153c/d. The first frequency is nearly equal to the previous result(Breger 1980), but the second one is much different. Our reanalysis of the previous data obtained by Guerrero el al.(1979) indicates that the previous result of $f_s$=5.95c/d might be uncertain; it was not detected in the power spectrum. Also it turns out that our second frequency could not be fitted to the previous data and the reanalyzed frequency($f_2$=7.8813c/d) of the previous data was poor-fitted to our data. Therefore we suggest that the second frequency which might be newly excited in the nonradial mode, has been changed over the last eighteen years.

• Journal of Astronomy and Space Sciences
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• 제22권3호
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• pp.211-222
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• 2005

Results of 6 nights of CCD VR photometry of the nova-like variable V603 Aquilae (Nova Aquilae 1918) obtained at the Mallorcian 35-cm telescope in July 2004 are reported. The ephemeris for the superhump maximum is Max.HJD=2453213.60546(96)+0.14813(10)E. The waves with $3.^d9,\;1.^d4,\;0.^d135$ are statistically significant, which may be interpreted as the negative superhump-orbital, the beat periods (negative superhump- positive superhump) and the negative superhump with low amplitude, respectively. Another possible time-scale is $0.^d8,$ which has no coincidence with the beat periods. Quasi-periodic oscillations with an effective period of 18 minutes have been detected, which are close to 15.6 minutes reported by some authors. Their effective semi-amplitudes are $^m.045\;and\;0^m.051$ for V and R, respectively. This corresponds to the 0.12 mag excess in the color index V-R as compared with the mean color, which can be understood as the pulsed emission in the hotter inner parts of the accretion disk, similar to that observed in TT Ari and MV Lyr.

• 천문학회지
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• 제43권5호
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• pp.141-152
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• 2010

UBV I CCD photometry is obtained for the open clusters NGC 4609 and Hogg 15 in Crux. For NGC 4609, CCD data are presented for the first time. From new photometry we derive the reddening, distance modulus and age of each cluster - NGC 4609 : E(B-V ) = $0.37{\pm}0.03$, $V_0-M_V=10.60{\pm}0.08$, log $\tau$= 7.7 $\pm$ 0.1; Hogg 15 : E(B - V ) = 1.13 $\pm$ 0.11, $V_0-M_V$ = 12.50 $\pm$ 0.15, log $\tau$ $\lesssim$ 6.6. The young age of Hogg 15 strongly implies that WR 47 is a member of the cluster. We also determine the mass function of these clusters and obtain a slope $\Gamma$ = -1.2 ($\pm$0.3) for NGC 4609 which is normal and a somewhat shallow slope (${\Gamma}=-0.95{\pm}0.5$) for Hogg 15.

• 천문학회지
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• 제34권3호
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• pp.143-147
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• 2001

UBVI CCD photometry of open cluster NGC 2324 is presented. C-M diagrams of this cluster show well-defined main sequence with a red giant clump centered at B - V =1.05, V =13.45. We derived the major cluster characteristics; E(B - V)=0.17$\pm$0.12 from color-color diagram and mean color of red giant clump stars, (m - M)o=13.1$\pm$0.1 from zero age main sequence fitting, and [Fe/H]$\~$-0.32 from comparison the theoretical model developed by Bertelli et al. (1994) to the observed C-M diagrams. We estimate the age of NGC 2324 to be log t$\~$8.8 by applying isochrone fitting and morphological age index method.

• Journal of Astronomy and Space Sciences
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• 제21권3호
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• pp.191-200
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• 2004

The accuracy of CCD observations obtained at the Korean 1.8m telescope has been studied. Seventeen comparison stars in the vicinity of the cataclysmic variable BG CMi have been measured. The 'artificial' star has been used instead of the 'control' star, what made possible to increase accuracy estimates by a factor of 1.3-2.1 times for 'good' and 'cloudy' nights, respectively. The algorithm of iterative determination of accuracy and weights of few comparison stars contributing to the artificial star, has been presented. The accuracy estimates for 13-mag stars are around $0.^m002$ mag for exposure times of 30 sec.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 1992년도 한국우주과학회보 제2권1호
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• pp.14.2-14
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• 1993

We present UBV CCD Photometry of the very metal-poor globular duster M3O,covering a region of r f 100 arcsec from the duster center. The data was obtained from the 40 inch telescope at Mt Soomlo Siding Spring Observator in August 1992. We used DAOPHOT CCD reudction package for data reduction to obtain Color-Magnitude Diagram(CMD). We have determined some fludamental parameters of the globular Ouster such as metal abundance, helium abundance and distance from the CMD. finally, we have attempted to determine the age of M3O using the revised Yale isochrones.

• 한국지구과학회지
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• 제27권6호
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• pp.670-676
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• 2006

[ ${\delta}$ ] Scuti형 변광성 HR 2707에 대해 한국교원대학교 청람천문대의 40 cm 카세그레인식 반사 망원경과 1K CCD(AP8p)를 사용하여 2001년 11월 13일부터 2002년 2월 20일까지 45일간 시계열 관측을 수행하였다. B, V필터를 이용한 측광 관측으로부터 3,011장의 V필터 영상과 6,562장의 B 필터 영상을 획득하였다. 이들 자료 중 2002년 1월의 7일간 V 필터 관측 자료는 국제공동 관측에 사용되었다(Lopez de Coca et al., 2003). 변광성의 맥동 주파수를 검출하기 위하여 이산 푸리에 변환(DFT)과 선형 최소자승법을 이용하여 8개의 맥동 주파수를 찾았으며, 이전 관측 자료에서 얻어진 주파수와 비교하여 HR 2707의 진짜 맥동 주기는 Lopez de Coca et at.(2003)의 연구에서 얻은 $f_1,\;f_2,\;f_3,\;f_4,\;f_5$의 5개의 주기와 우리의 연구로부터 얻은 $f_4$까지 6개로 결정하였다.

• 천문학회지
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• 제32권2호
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• pp.91-107
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• 1999

We present BVRI CCD photometry and near-infrared K photometry of the intermediate-aged open cluster NGC 7790. The reddening, E(B - V) = 0.54 $\pm$ 0.05 and the distance modulus, (m - M)o = 12.45 $\pm$ 0.10 for the cluster were determined by zero-age-main-sequence fitting and theoretical isochrone fitting using not only (V, B - V), (V, V - 1), (V, V - R) but also (V, V - K) color-magnitude diagrams. The reddening corresponded approximately to the average value derived from previous studies, while the distance modulus was found to be almost midway between the CCD photometric results of Romeo et al. (1989) and those of Mateo & Madore (1988). We have used four colors to distinguish members from field stars. The expected colors were calculated using the derived distance modulus, and were then were compared with the observed colors (B - V), (V - 1), (V - R), and (V - K). Thus, a color excess E(B - V) for each star was determined which could give the minimum difference between the calculated and observed colors. Single and binary members of the cluster were determined on the basis of the E(B - V) distribution of stars.

• 천문학회지
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• 제29권spc1호
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• pp.61-62
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• 1996

The photometry is reported for galaxies in two clusters A1983, 2065 with redshifts 0.046, 0.072 respectively. The luminosity segregation is observed only within a magnitude from the brightest galaxy. The alignment of the galaxy major axis is observed in the Corona Borealis cluster. The intermediate distance clusters (0.05 < z < 0.15) will be studied by CCD mounted on 125cm RCh and 70cm meniscus type telescopes.

• 천문학회보
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• 제26권1호
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• pp.47.1-47.1
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• 2001