• Publications of The Korean Astronomical Society
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• v.19 no.1
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• pp.27-31
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• 2004

Through time-series CCD photometry using a 155mm refractor, we found a new $\delta$ Scuti type variable star, HD 235428, near a known bright $\delta$ Scuti type star, DQ Cep. We performed follow-up observations using a 61cm telescope at Sobaeksan Optical Astronomy Observatory. Four frequencies have been derived by multiple-frequency analysis, which are 15.804, 5.498, 15.351 and 24.516cycle $day^{-1}$, respectively. V-amplitude of HD 235428 is ${\Delta} V$ = 0.026.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.51.3-51.3
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• 2018

MBM 110 is one of the molecular clouds at high Galactic latitude discovered by Magnani et al., and is one of a dozen cometary clouds in the Orion-Eridanus superbubble. We have conducted optical photometry and spectroscopy for a comprehensive study of the region. Recently released Gaia DR2 astrometric data as well as WISE mid-infrared data were used for the complete census of member stars. We select 17 member stars with $H{\alpha}$ emission and/or Li absorption. The total mass of stars in the region is only about $16M{\odot}$. We found that the star formation efficiency in the region is less than 5%. We discuss the origin of the cloud and the star formation history in MBM 110.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.82.2-82.2
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• 2011

Infra-Red Dark Clouds (IRDCs) seen silhouette against the bright Galactic background in mid-IR are a class of interstellar clouds that are dense and cold with very high column densities. While IRDCs are believed to be the precursors to massive stars and star clusters, individual IRDCs show diverse star forming activities within them. We report a remarkable example of such cloud, the IRDC at ${\Gamma}53.2^{\circ}$, and star formation activity in this cloud. The IRDC was previously identified in part as three separate, arcmin-size clouds in the catalogue of MSX IRDC candidates, but we found that the IRDC is associated with a long, filamentary CO cloud at 2 kpc from the Galactic Ring Survey data of $^{13}CO$ J = 1-0 emission, and that its total extent reaches ~ 30pc. The Spitzer MIPSGAL 24mm data show a number of reddened mid-IR sources distributed along the IRDC which are probably young stellar objects (YSOs), and the UWISH2 $H_2$ data (2.122mm) reveal ubiquitous out flows around them. These observations indicate that the IRDC is a site of active star formation with YSOs in various evolutionary stages. In order to investigate the nature of mid-IR sources, we have performed photometry of MIPSGAL data, and we present a catalogue of YSOs combining other available point source catalogues from optical to IR. We discuss the evolutionary stages and characteristics of YSOs from their IR colors and spectral energy distributions.

• Journal of The Korean Astronomical Society
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• v.32 no.2
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• pp.109-117
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• 1999

UBVI CCD photometry has been obtained for a region around the Wolf-Rayet star WR 12. We found two young stellar associations in the observed field: the nearer one comprises the field members of Vela OBI association at d = 1.8kpc, while the farther one is the young open cluster Bochum 7 (Bo 7) at d = 4.8kpc. The stars associated with Bo 7 showed no central concentration which suggests that Bo 7 is not a young open cluster but simply a local concentration in the density of young stars belonging to the OB association (Vel OB3). These two associations have similar ages but remarkably different mass function slopes ($\Gamma$ = -2.1 $\pm$ 0.3 for Vel OBI and -1.0 $\pm$ 0.3 for Bo 7). The stars in Vel OBI shows an evident age spread (${\Delta}T\~ 9Myr$). We also found two strong H$\alpha$ emission stars - WR 12 and $\sharp$1066 - from narrow band H$\alpha$ photometry.

• Journal of The Korean Astronomical Society
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• v.26 no.1
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• pp.33-45
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• 1993

We have conducted surface photometry of a spiral galaxy NGC4419, by making use of photographic plates in U, B, V and R-bands taken by 105cm Schmidt Camera at Kiso Observatory. Two dimensional surface brightness distributions as well as luminosity profiles along the major axis are examined in detail to decipher the morphological properties of the galaxy. Analysis of the color distributions of NGC4419 shows that B-V and U-B colors remain constant throughout the galaxy with a weak trend of blue bulge in B-V color. The blue bulge might indicate an active star formation in the nucleus of NGC4419. For a quantitative analysis of the luminosity distribution of NGC4419, the observed luminosity profiles are decomposed into bulge and disk components, assuming the bulge component to follow de Vaucouleurs $\gamma^{1/4}-law$ while the disk component is assumed to be exponential. The fitting generally fails at the central part and at the shoulder near r = 15' where bulge and disk components overlap. The failure at the central part cannot be attributed wholly by the seeing disk since the core-radius of the central plateau is much larger than the width of point spread function. The failure at shoulder could be due to the luminosities from the spiral arms.

• 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.35 no.1
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• pp.9-28
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• 2002

We present UBVI CCD photometry of the stellar contents and globular cluster(GC) candidates in the spiral galaxy NGC 300 in the Sculptor group. Color-magnitude diagrams for 18 OB associations having more than 30 member stars are presented. The slope of the initial mass function for the bright stars in NGC 300 is estimated to be ${\Gamma}= -2.6{\pm} 0.3$. Assuming the distance to NGC 300 of (m - M)o = 26.53 $\pm$ 0.07, the mean absolute magnitude of three brightest blue stars is obtained to be < $M_v^{BSG}$ (3) > = -8.95 mag. We have performed search for GCs in NGC 300 and have found 17 GC candidates in this galaxy. Some characteristics of these GC candidates are discussed.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.41.2-41.2
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• 2015

We have performed deep wide-field CCD photometry of the young open cluster IC 1805 in the famous star forming region W4, and obtained photometric data for more than 91,000 stars in the field of IC 1805 based on observations with the 3.6m CFHT and the AZT-22 1.5m telescope at Maidanak Astronomical Observatory in Uzbekistan. The photometric data cover an area $43^{\prime}{\times}45^{\prime}$ which is far larger and far deeper than any other optical observations made for the cluster. In order to select the young stellar objects with mid-IR excess emission, we have performed mid-IR photometry of the cluster using the archival images obtained with the Spitzer Space Telescope IRAC and MIPS instruments. From a preliminary analysis of the data, we determined the reddening law ($R_V=3.02{\pm}0.05$), distance modulus ($V_0-M_V=11.9{\pm}0.2$), and the spatial distribution of members.

• Journal of The Korean Astronomical Society
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• v.29 no.2
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• pp.255-268
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• 1996

We present VR CCD photometry and long-slit spectroscopy of a late type spiral galaxy NGC 7678. The grey scale images and isophotal maps illustrate the presence of a weak bar from which spiral arms emerge. There are many HII regions along the spiral arms, but bright giant HII regions are more concentrated in the massive southern arm. The bright compact nucleus of NGC 7678 is bluer than bulge and bar. The spectral features of the nucleus and HII regoins are very similar but the nuclear spectra shows higher $[NII]{\lambda}6583/H_\alpha$ than those of the HII regions. The nucleus of NGC 7678 seems to be intermediate type between HII region nulcei and LINERs by the ratio of $[NII]{\lambda}6583/H_\alpha$, but it is more likely to be HII region-like nucleus if we consider the $[NII]{\lambda}6716,6731/H_\alpha$ together. The star formation rate is estimated to be about $0.2 M_\bigodot\;yr^{-1}$ based on the $H_\alpha$ flux.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.75.2-75.2
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• 2019

This poster introduces the ongoing "Narrow-band Ca Photometry for Dwarf Spheroidal Galaxies" project and presents the latest results. The project aims to explain the formation and evolution of dwarf spheroidal galaxies by examining the structural properties of stellar populations as a function of metallicity. To overcome the lack of stars with known spectroscopic metallicities for dwarf spheroidal galaxies, we apply the hk index as a photometric metallicity indicator to three galaxies-Draco, Sextans, and Canes Venatici I. For all three galaxies, we found that metal-poor and metal-rich groups of red-giant-branch stars have distinct spatial distributions, in which metal-rich stars are centrally concentrated while metal-poor stars are relatively dispersed. In Sextans, we found an off-centered peak of metal-poor stars which is presumed to be a disrupting star cluster in this galaxy. We will discuss the implications of our results for the dwarf galaxy formation and possible directions on future work of this project.