• Journal of The Korean Astronomical Society
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• v.35 no.1
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• pp.29-34
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• 2002

We have conducted UBVI CCD photometry of an intermediate-age open cluster NGC 559 to investigate the effect of dynamical evolution on the stellar distributions in NGC 559. Our photometry allows better estimates of distance and age of the cluster owing to much deeper photometry (V $\le$ 21) than previous ones. It is found that the luminosity function and mass function as well as the spatial stellar distributions are affected by the dynamical evolution. Mass segregation leads to the central concentration of the high mass stars, which results in the flattened mass function inside the half mass radius.

• Journal of The Korean Astronomical Society
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• v.31 no.1
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• pp.39-50
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• 1998

We present UBV CCD photometry of Be 2, previously unstudied open cluster. Our photometry covers a field of $3'.2\times3'.8$ of the sky centered on the cluster, which is slightly smaller than the cluster diameter estimated to be about 260'. We have determined the reddening, distance, age and metallicity of the cluster by fitting the Pad ova isochrones to the observed stellar distributions in color-magnitude diagram as well as main sequence fitting: $E(B-V)=0.8\pm0.05,\;(m-M)_o=13.6\pm0.1,\;log(t) =8.9\pm0.1$, and Z=0.008. The present photometry shows that Be 2 is a distant open cluster of intermediate age. that it is a distant intermediate-age open duster.

• The Bulletin of The Korean Astronomical Society
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• v.24 no.1
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• pp.29-29
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• 1999

• Journal of Astronomy and Space Sciences
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• v.18 no.1
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• pp.55-62
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• 2001

We present VRI CCD photometry of W UMa type binary TY UMa. The light curves show that the secondary minimum is deeper than the primary minimum and the maximum I ($0.^{p}25$)is $0.^{m}023$ brighter than the maximum II ($0.^{p}75$). The V light curve has been analyzed and the photometric solutions have been determined by the method of Wilson & Devinney differential correction. We adopted the spot model to explain the asymetric light curve.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.79-80
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• 1996

We performed CCD surface photometry in B,V,R and I filters for three southern spiral galaxies:ESO598-G009,NGC1515 and NGC7456. Isophotal map, luminosity profile, ellipticity profile and position angle profile were obtained for these galaxies using SPIRAL package. The results show that one of the galaxies, ESO598-G009 has relatively large bulge component and changes in position angle due to spiral arms. The NGC7456 has very small bulges; and the isophotal map of the NGC1515 shows that it is a typical spiral galaxy with bar.

• Journal of The Korean Astronomical Society
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• v.31 no.1
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• pp.67-74
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• 1998

The VI CCD photometry is made for stars in the globular cluster M22 down to $V\approx19^m,\;I\approx18^m$. In the color-magnitude diagram (CMD), red giant branch (RGB), asymtotic giant branch (AGB) and blue horizontal branch (BHB) are well defined. The luminosity functions (LF) of RGB, AGB and BHB stars are derived, discussing deficient gaps and bumps in the CMD. The anomalously wide RGB seen in the BV photometric system is found to disappear in the VI photometric system.

• Journal of The Korean Astronomical Society
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• v.29 no.2
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• pp.137-156
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• 1996

NGC 6716 is an intermediate-age open cluster in Sagittarius. In this paper, we present the new UBV CCD photometry of the stars in the cluster, which is deeper than previous ones. From the color-color diagram and the color-magnitude diagram, we derived a reddening $E_{B- V} = 0.17\pm0.03$ and a distance modulus of the cluster, $(V - Mv)_o = 9.2\pm0.1$. An age of the cluster is estimated as $8\pm10^7 yrs$ from the latest isochrone. Luminosity function and mass function of the cluster are derived. The gradient of the mass function of bright stars is a bit steep, $\Gamma = -1.85\pm0.05$, and there is no distinct bump and dip in the mass function.

• Journal of The Korean Astronomical Society
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• v.36 no.4
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• pp.261-270
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• 2003

We have conducted a V-band CCD surface photometry of 68 disk galaxies to analyze the bulge morphology of nearby spirals. We classify bulges into four types according to their ellipticities and the misalignments between the major axis of the bulge and those of the disk and the bar: spherical, oblate, pseudo triaxial, and triaxial. We found that one third of the bulges are triaxial and they are preponderant in barred galaxies. The presence of the triaxial bulges in a significant fraction of unbarred galaxies as well as in barred galaxies might support the secular evolution hypothesis which postulates that the bar driven mass inflow leads to the formation of triaxial bulges and the destruction of bars when sufficient mass is accumulated in the central regions.

• Journal of The Korean Astronomical Society
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• v.28 no.2
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• pp.119-137
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• 1995

The $UBVI_{KC}$ CCD photometry was performed in the central region(${\sim}20'{\times}20'$) of the extremely young open cluster IC1805. Member stars were selected in the (B-V)-(U-B) and (V-I)-(B-V) color-color planes. Applying recent stellar evolutionary models, we derived the age, age-spread, and initial mass function(IMF) of the cluster. IC1805 was found to be an extremely young($t_{age}{\sim}1.5Myr$) and has a flat IMF with the slope of ${\Gamma}=-1.0{\pm}0.2$.

• Journal of The Korean Astronomical Society
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• v.28 no.2
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• pp.177-196
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• 1995

We present UBV CCD photometry of the double cluster NGC 1850 located at the NW edge of the bar of the Large Magellanic Cloud. The color-magnitude diagram shows that NGC 1850 has a prominent population of massive core-He burning stars which is incomparably richer than any other known star clusters. The reddening is estimated from the (U-B) - (B-V) diagram to be E(B - V) = $0.15{\pm}0.05$. We have estimated the ages of NGC 1850 and a very compact blue star cluster (NGC 1850A) located at ${\sim}30''$ west of NGC 1850 using isochrones based on the convective overshooting models: $80{\sim}10$ Myrs and $5{\sim}2$ Myra, respectively. Several evidence suggest that it is probably the compact cluster NGC 1850A that is responsible for the arc-shaped nebulosity (Henize N 103B) surrounding the east side of NGC 1850.