• 천문학회보
• /
• 제21권
• /
• pp.18.1-18.1
• /
• 1996

• 천문학회보
• /
• 제27권1호
• /
• pp.60-60
• /
• 2002

• 천문학회보
• /
• 제19권
• /
• pp.8.2-9
• /
• 1994

• 천문학회보
• /
• 제19권
• /
• pp.27.1-27.1
• /
• 1994

• Journal of Astronomy and Space Sciences
• /
• 제18권1호
• /
• pp.7-14
• /
• 2001

Red giant branch shape and the luminosity of horizontal branch on the (V-I)-V CMD are used to derive the metallicity the globular cluster NGC 5053. The metallicities of NGC 5053 derived by SMR method ([Fe/H]=-2.62$\pm$0.07) and the relation between[Fe/H] and $(V-I)_{0.g}$ ([Fe/H]=-2.50) are in good agreement with previously determined values. This result confirms that the morphologies of RGB and HB on the (V-I)-V CMDs can be good indirect photometric metallicity indicators of galactic globular clusters.

• 천문학논총
• /
• 제16권1호
• /
• pp.37-42
• /
• 2001

We developed an observation program for a 2K CCD camera, which was newly attached at the SOAO (Sobaeksan Optical Astronomy Observatory) 61cm telescope. The program was designed to control the telescope as well as the CCD camera and to monitor the CCD image quality, with very easy under the window-based graphical user interface (GUI). Furthermore, applying the automated differential photometric algorithm, we can obtain the instrumental magnitudes of several variable and comparison stars in real-time. Simultaneous photometry enables us to get precise differential magnitudes of variable stars even if the weather condition is not photometric. This new observation system has been using for many astronomical observations from September, 2001.

• 천문학회지
• /
• 제31권1호
• /
• pp.51-65
• /
• 1998

We present B VRI CCD surface photometry for the central $(6'.35\times6'.35)$ regions of the dwarf elliptical galaxies NGC 185 and NGC 205 in the Local Group. Surface brightness profiles of NGC 185 (R<225') and NGC 205 (R<186') show excess components in the central regions. The colors of NGC 185 get bluer inward at R<25', while they remain constant at $R\geq25'$. The colors of NGC 205 get bluer inward at 1'$\approx10^5\; L_\bigodot$. Distributions of dust clouds in the central regions of the two galaxies are also investigated.

• 천문학회지
• /
• 제35권2호
• /
• pp.87-95
• /
• 2002

We have conducted VI CCD photometry of the open cluster NGC 6819 in order to understand the effects of dynamical evolution in old open clusters. Our photometry covers 18' $\times$ 18' on the sky, centered on the cluster, which seems to cover the whole cluster field. Our photometry reaches down to V $\approx$ 20.5, which allows us to analyze the luminosity function and spatial distribution of stars brighter than Mv $\approx$ 8.5. There is a clear evidence for mass segregation in NGC 6819, i.e., the giants and upper main-sequence stars are concentrated in the inner regions, whereas the lower main-sequence stars distribute almost uniformly throughout the cluster. The luminosity function of the main-sequence stars of NGC 6819 is almost flat. The flat luminosity function indicates that a large number of low mass stars has escaped from the cluster unless its initial mass function is much different from the Salpeter type (${\phi}(m){\propto} m^{-(1+x)},x = 1.35$).

• 천문학회지
• /
• 제31권2호
• /
• pp.141-160
• /
• 1998

We have conducted BV RI CCD surface photometry of three spiral galaxies ESO 598-G009, NGC 1515 and NGC 7456. In order to understand the morphological properties and luminosity distribution characteristics for each galaxy, we derived isophotal map, position angle profile, ellipticity profile, luminosity profile, color profile and color contour map. ESO 598-G009, which has a bright bulge component and a ring, shows a trace of gravitational interaction. NGC 1515 is a spiral galaxy with a bar and dust lane. NGC 7456 shows typical characteristics of a late type spiral galaxy.

• 한국지구과학회지
• /
• 제34권5호
• /
• pp.415-427
• /
• 2013

We performed a BVR photometric survey for the entire Small Magellanic Cloud (~26 deg 2 ) with a mosaic system, Wide Field Imager (WFI), covering three seasons: September and October 2001 and November 2002. Through the usual data reduction procedures, we present ~0.73 million catalogue stars brighter than 19 magnitude in B amongst a total of ~1.3 million and compare them with published astrometry and photometry results. We found that the average differences between our and the published data are ~0.7 arcsec in astrometry and 0.065, 0.054, and 0.163 in B, V, and R, respectively, in photometry. In addition, using the 2dF spectroscopic data from Evans et al. (2004), we determined the color excesses in (B-V) and (V-R) to be $0.086{\pm}0.156$, and $0.065{\pm}0.112$, respectively, while for the distance modulus, we obtained $18.55{\pm}1.05$.