• Journal of Astronomy and Space Sciences
• /
• 제7권2호
• /
• pp.105-111
• /
• 1990

Stars in M 68 from the observed-magnitude diagrams with CCD were integrated to find any radial gradient. The result shows that M 68 has a slightly bluer core. The main cause of these calculated radial color variations seems to come from the random distribution of ginants.

• 천문학회보
• /
• 제5권
• /
• pp.13.2-13.2
• /
• 1980

• 천문학회보
• /
• 제35권1호
• /
• pp.54.2-54.2
• /
• 2010

The most massive galactic globular cluster, $\omega$ Cen has been observed using recently mounted WFC3/UVIS cameras of Hubble Space Telescope at both near-UV and optical bands. We present the photometry of stars in the central region of $\omega$ Cen in F225W, F275W and F336W bands. The near-UV color-magnitude diagrams and color-color diagrams of stars in $\omega$ Cen show multiple red giant branches and main sequences as already discovered in both ground-based and HST/ACS observations in the optical bands. We modelled the stellar populations of $\omega$ Cen using Yonsei Isochrone, where $\alpha$-particles and helium enhancement processes have been included properly. We compare the best-fit stellar populations obtained from the current near-UV observations to the suggested stellar population models based on optical band data. We also discuss the methodological issues arising when dealing with the near-UV observations; red-leak in near-UV filters and the huge interstellar extinction in near-UV bands compared to the optical bands and its non-linear effect in color-magnitude diagrams.

• 천문학회지
• /
• 제30권1호
• /
• pp.1-11
• /
• 1997

Near infrared JHK magnitudes are presented for two hundred two high proper motion stars. We have observed high proper motion stars in the near-infrared bands(JHK) using the COB detector on the Kitt Peak 1.3m, 2.1m and 4m telescopes. The observations and data reduction procedures are described. The infrared color magnitude diagram and color-color diagrams for the program stars are presented.

• 천문학회지
• /
• 제29권spc1호
• /
• pp.75-76
• /
• 1996

We have started multi-color imaging program of nearby galaxies since last year and present preliminary result here. We selected 12 nearby galaxies classfied from E to Sab type and observed in BVRIJHK' bands. Photomtric parameters such as isophotal diameter, axial ratio, isophotal magnitude were measured and observed colors were compared with theoritical model. We find a standard evolution model agrees well with observed results.

• 천문학논총
• /
• 제27권4호
• /
• pp.129-134
• /
• 2012

The North Ecliptic Pole (NEP) Wide survey covered about 5.4 $deg^2$, a nearly circular area centered on the NEP, using nine passbands of InfraRed Camera (IRC). We present the photometric properties of the data sets, and the nature of the sources detected in this field. The number of detected sources varied according to the filter band: with about 109,000 sources in the NIR, about 20,000 sources in the MIR-S, and about 16,000 sources seen in the MIR-L channel. The $5{\sigma}$ detection limits are about 21 mag in the NIR and 19.5 - 18.5 mag in the MIR bands in terms of the AB magnitude. 50% completeness levels are about 19.8 mag at $3{\mu}m$, 18.6 mag at $9{\mu}m$, and 18 mag at $18{\mu}m$ band (in AB magnitude), respectively. In order to validate the detected sources, all of them are confirmed by matching tests with those in other bands. The 'star-like' sources, defined by the high stellarity and magnitude cut from the optical ancillary data, appear statistically to have a high probability of being stars. The nature of the various types of extragalactic sources in this field are discussed using the color-color diagrams of the NIR and MIR bands with the redshift tracks of galaxies providing useful guidelines.

• 한국의류학회지
• /
• 제44권1호
• /
• pp.68-83
• /
• 2020

This study suggests a method to predict the color appearance of textiles that shifts depending on illumination variations. The suggested method allows the calculations of lightness, chroma, and hue appearance values from the spectral reflectance values of the textile and illuminant. The accuracy of the method was evaluated through numerical and statistical comparisons between the predicted and the measured color appearance values of 24 fabric samples under CIE standard illuminant D65. As a result, there were excellent agreements between the two data sets with the error values close to zero. The predicted color appearance values of 24 samples under two illuminating (color temperature-luminance) conditions, 2700 K-100 cd/㎡ and 6500 K-100 cd/㎡, were then compared to prove the significant effect of illumination on the color appearance of textiles. The color appearance values were also compared with spectrophotometrically measured physical color attributes, that is, true colors of the samples. The physical color attributes of samples were unchanged; however, differences in color appearance under different conditions were generally much larger than the suprathreshold color difference tolerances discussed in the color science literature. Finally, the magnitude of the illumination effect depending on the physical color attributes of samples was also analyzed.

• 천문학회지
• /
• 제31권1호
• /
• pp.67-74
• /
• 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.

• 천문학회보
• /
• 제35권2호
• /
• pp.29.1-29.1
• /
• 2010

Recent observations reveal that some early-type galaxies show a color-magnitude relation of blue globular clusters (GCs) in the color-magnitude diagrams, which is referred to as 'blue tilt'. This phenomenon is interpreted as a mass-metallicity relation -- metallicities of blue GCs increase with increasing mass, and thus provides a crucial clue to the chemical enrichment processes of GCs as a function of their mass. However, some galaxies show 'non-tilt' or even 'reverse blue tilt' on the blue GC sequence, and thus the origin of blue tilt still remains a puzzle. In this study, we put forward the theoretical explanation for the phenomenon and discuss its implications towards galaxy formation scenarios.

• 천문학논총
• /
• 제30권2호
• /
• pp.539-541
• /
• 2015

We present a new tool for studying the spectral energy distributions (SEDs) and color-magnitude diagrams (CMDs) of galaxies and star clusters, BINARY STAR TO FIT (BS2fit). A key feature of this tool is that it takes the effects of binaries, stellar rotation and star formation history into account. It can be used to determine many parameters, including distance, extinction, binary fraction, rotational star fraction, and star formation history. Because more factors are included than in previous tools, BS2fit can potentially give new insight into the properties of galaxies and clusters. One can contact the authors for cooperation and helps via.