• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.6
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• pp.18-25
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• 2006

Existing outdoor lighting evaluation methods for the city beautification at night, the measurements are limited by one point to analyze the photometric data. However, this methods could not represent the diversity of photometric result from the distance. This study aims to propose the new outdoor lighting evaluation method of structure surface luminance in accordance with the measuring distance. For the purpose, the field measurement and simulation of an illuminated structure were conducted by CS-100, Digital Photometry Instrument ProMetric 1400, and the Lightscape v 3.2 from the distance of 100[m], 300[m], 500[m]. The result shows that evaluation of the surface luminance by the distance should be measured from about 100[m] of an illuminated object for getting the familiar result from computer simulation.

• Journal of The Korean Astronomical Society
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• v.51 no.4
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• pp.73-88
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• 2018

We present a sample of 54 disk galaxies which have well developed extraplanar structures. We selected them using visual inspections from the color images of the Sloan Digital Sky Survey. Since the sizes of the extraplanar structures are comparable to the disks, they are considered as prominent stellar halos rather than large bulges. A single $S{\acute{e}}rsic$ profile fitted to the surface brightness along the minor-axis of the disk shows a luminosity excess in the central regions for the majority of sample galaxies. This central excess is considered to be caused by the central bulge component. The mean $S{\acute{e}}rsic$ index of the single component model is $1.1{\pm}0.9$. A double $S{\acute{e}}rsic$ profile model that employs n = 1 for the inner region, and varying n for the outer region, provides a better fit than the single $S{\acute{e}}rsic$ profile model. For a small fraction of galaxies, a $S{\acute{e}}rsic$ profile fitted with n = 4 for the inner region gives similar results. There is a weak tendency of increasing n with increasing luminosity and central velocity dispersion, but there is no dependence on the local background density.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.58.2-58.2
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• 2015

We present a library of high spectral resolution (R ~ 40,000) and high signal-to-noise ratio (S/N ~ 200) near-infrared spectra of ~50 late-type stars. The spectra of late-type stars were obtained with Immersion GRating INfrared Spectrograph (IGRINS) covering the full H and K band. The stars are mainly from MK standard stars which have well-defined spectral types and luminosity classes and cover wide ranges of effective temperatures and surface gravities. The spectra are corrected for telluric absorption lines and absolutely flux calibrated using the Two Micron All Sky Survey (2MASS) photometry. In this work, we present the preliminary results of spectroscopic diagnostics for stellar physical parameters. Our ultimate goal is to provide a library of near-infrared spectra of standard stars, which covers all spectral types and luminosity classes, with a high spectral resolution and high signal-to-noise ratio.

• Journal of Astronomy and Space Sciences
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• v.16 no.2
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• pp.91-104
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• 1999

We use BV CCD images to investigate the reality of the color gradient within a King type globular cluster NGC 7089. Surface photometry shows that there is a strong radial color gradient in the central region of the cluster in the sense of bluer center with the amplitude of ~0.39 $\pm$ 0.07 mag/$arcsec^2$ in (B - V). In the outer region of the cluster, however, the radial color gradient shows a reverse case, i.e., redder toward the center. (B - V) color profile which was derived from resolved stars in VGC 7089 field also shows a significant color gradient in the central region of the clusters, indicating that lights from the combination of red giant stars and blue horizontal branch stars cause the radial color gradient. Color gradient of the outer region of NGC 7089 may be due to the unresolved background of the cluster. Similar color gradients in the central area of clusters have been previously observed exserved exclusively in highly concentrated systems classified as post core collapse clusters. We caution, however, to confirm the reality of the color gradient from resolved stars, we need more accurate imaging data of the cluster with exceptional seeing condition because the effect of completeness correlates with local density of stars.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.77.1-77.1
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• 2012

We present high-resolution radial velocity measurements of K2 giant ${\varepsilon}$ CrB from February 2005 to January 2012 using the fiber-fed Bohyunsan Observatory Echelle Spectrograph at Bohyunsan Optical Astronomy Observatory. We find that the RV measurements for ${\varepsilon}$ CrB exhibit a periodic variation of 418 days with a semi-amplitude of 129 m/s. There is no correlation with RV measurements and inhomogeneous surface features by examining chromospheric activity indicator (Ca II H region), the Hipparcos photometry, and bisector velocity span. Thus, Keplerian motion is the most likely explanation, which suggests that the RV variations arise from an orbital motion. Assuming a possible stellar mass of 1.7 $M_{\odot}$, for ${\varepsilon}$ CrB, we obtain a minimum mass for the planetary companion of 6.7 $M_{Jup}$ with an orbital semi-major axis of 1.3 AU, and an eccentricity of 0.11. We support that more massive stars harbor more massive planetary companions in giant hosting planetary companions (Dollinger et al. 2009), as well as, we discuss the frequency of detected planetary companions with the metallicity distribution in giant (Pasquini et al. 2007; Quirrenbach et al. 2011).

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.51.2-51.2
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• 2018

Polarimetry is a powerful technique to investigate the physical properties of surface materials on airless bodies in the solar system. It is known that the degree of linear polarization changes as a function of the phase angle (the angle between Sun-target-Observer). Especially, the dependency of the polarization degree at large phase angle allows us to obtain information related to the particle size and porosity, which is difficult to be determined via other observation techniques (i.e., photometry and spectroscopy). However, despite the advantage, only a few asteroids were observed with polarimetric devices at large phase angles. Here, we present our new polarimetric research of Near-Earth Asteroids (NEAs) observed at the large phase angles. Among the NEAs, we focus on S- and Q-type asteroids, which include: (331471) 1984 QY1, (90075) 2002 VU94, and (66391) 1999 KW4. The observation was conducted using the Pirka 1.6-m Telescope at the Nayoro Observatory of Hokkaido University at the phase angles ${\alpha}{\sim}100degree$, which provides us the maximum polarization degrees of these objects. Considering the observational results together with two objects ((1566) Icarus and (4179) Toutatis) in reference papers [1], [2], we will discuss the implication of the regolith size on their surfaces.

• Journal of Astronomy and Space Sciences
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• v.36 no.2
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• pp.75-86
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• 2019

UV Psc is a typical RS CVn type system undergoing dynamic chromosphere activity. We performed photometric observations of the system in 2015 and secured new BVR light curves showing well-defined photometric waves. In this paper, we analyzed the light curves using Wilson-Devinney binary code and investigated the orbital period of the system. The combination of our light curve synthesis with the spectroscopic solution developed by previous investigators yielded the absolute parameters as: $M_1=1.104{\pm}0.042M_{\odot}$, $R_1=1.165{\pm}0.025R_{\odot}$, and $L_1=1.361{\pm} 0.041L_{\odot}$ for the primary star, and $M_2=0.809{\pm}0.082M_{\odot}$, $R_2=0.858{\pm}0.018R_{\odot}$, and $L_2=0.339 {\pm}0.010L_{\odot}$ for the secondary star. The eclipse timing diagram for accurate CCD and photoelectric timings showed that the orbital period may vary either in a downward parabolic manner or a quasi-sinusoidal pattern. If the latter is adopted as a probable pattern for the period change, a more plausible account for the cyclic variation may be the light time effect caused by a circumbinary object rather than an Applegate-mechanism occurring via variable surface magnetic field strengths.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.60.3-61
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• 2020

We perform disk-halo decomposition of the Large Magellanic Cloud (LMC) using a novel HI velocity field extraction method, aimed at better deriving its HI kinematics and thus the dark matter density profile. For this, we use two newly developed galaxy kinematic analysis tools, BAYGAUD and 2DBAT which have been used for the kinematic analysis of resolved galaxies from Australian Square Kilometre Array (ASKAP) observations like WALLABY which is an all-sky HI galaxy survey in southern sky. By applying BAYGAUD to the combined HI data cube of the LMC taken with the Australia Telescope Compact Array (ATCA) and Parkes radio telescopes, we decompose all the line-of-sight velocity profiles into an optimal number of Gaussian components based on Bayesian MCMC techniques. From this, we disentangle turbulent non-circular gas motions from the overall rotation of the galaxy. We then derive the rotation curve of the LMC by applying 2DBAT to the separated circular motions. The rotation curve reflecting the total kinematics of the LMC, dark and baryonic matters is then be combined with the mass models of baryons, mainly stellar and gaseous components in order to examine the dark matter distribution. Here, we present the analysis of the extracted HI gas maps, rotation curve, and J, H and K-band surface photometry of the LMC.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.249-262
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• 2004

The variations of the dynamical substructures of NGC 6934 have been investigated by means of performing point spread function stellar photometry and the surface photometry on BV CCD images of NGC 6934. Our results show that overall variations of ellipticity and position angle range in $0.02{\sim}0.08\;and\;-90^{\circ}{\sim}+90^{\circ}$, respectively out to three times the half light radius. The inner ($r_{eff}) substructures of NGC 6934 inferred from the variations of ellipticity and position angle are mainly affected by the bright red giant populations, while the effects of the other giant populations are weaker than those of the bright red giant populations. Horizontal branch populations and faint red giant star populations affect the dynamical substructures of NGC 6934 in the region of $r_h.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.44.1-44.1
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• 2016

The Sagittarius-Carina spiral arm in the Galaxy contains several massive young open clusters. We present a deep optical photometric study on the massive young open clusters in the Sagittarius-Carina arm, Westerlund 2 and the young open clusters in the ${\eta}$ Carina nebula. Westerlund 2 is a less studied starburst-type cluster in the Galaxy. An abnormal reddening law for the intracluster medium of the young starburst-type cluster Westerlund 2 is determined to be $R_{V,cl}=4.14{\pm}0.08$. The distance modulus is determined from zero-age main-sequence fitting to the reddening-corrected color-magnitude diagrams of the early-type members to be $V_0-M_V=13.9{\pm}0.14mag$. The pre-main sequence (PMS) members of Westerlund 2 are selected by identifying the optical counterparts of X-ray emission sources from the Chandra X-ray observation and mid-infrared emission sources from the Spitzer/IRAC (the Infrared Array Camera) observation. The initial mass function (IMF) shows a slightly flat slope of ${\Gamma}=-1.1{\pm}0.1$ down to $5M_{\odot}$. The age of Westerlund 2 is estimated to be. 1.5 Myr from the main-sequence turn-on luminosity and the age distribution of PMS stars. The ${\eta}$ Carina nebula is the best laboratory for the investigation of the Galactic massive stars and low-mass star formation under the influence of numerous massive stars. We have performed deep wide-field CCD photometry of stars in the ${\eta}$ Carina nebula to determine the reddening law, distance, and the IMF of the clusters in the nebula. We present VRI and $H{\alpha}$ photometry of 130,571 stars from the images obtained with the 4m telescope at Cerro Tololo Inter-American Observatory (CTIO). RV,cl in the η Carina nebula gradually decreases from the southern part (~4.5, around Trumpler 14 and Trumpler 16) to the northern part around Trumpler 15 (~3.5). Distance to the young open clusters in the ${\eta}$ Carina nebula is partly revised based on the zero-age main-sequence fitting to the reddening-corrected color-magnitude diagrams (CMDs) and the (semi-) reddening-independent CMDs. We select the PMS members and candidates by identifying the optical counterparts of X-ray sources from the Chandra Carina Complex Survey and mid-infrared excess emission stars from the Spitzer Vela-Carina survey. From the evolutionary stage of massive stars and PMS stars, we obtain that the northern young open cluster Trumpler 15 is distinctively older than the southern young open clusters, Trumpler 14 (${\leq}2.5 Myr$) and Trumpler 16 (2.5-3.5 Myr). The slopes of the IMF of Trumpler 14, Trumpler 15, and Trumpler 16 are determined to be $-1.2{\pm}0.1$, $-1.5{\pm}0.3$, and $-1.1{\pm}0.1$, respectively. Based on the RV,cl of several young open clusters determined in this work and the previous studies of our group, We suggest that higher RV,cl values are commonly found for very young open clusters with the age of < 4 Myr. We also confirm the correlation between the slope of the IMF and the surface mass density of massive stars.