• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.97.1-97.1
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• 2012

NIR Emission lines from singly-ionized Iron, in particular [Fe II] $1.64{\mu}m$, are good tracer of dense atomic gas in star-forming regions, around evolved stars, and in supernova remnants. We are imaging about 180 square degrees along the Galactic Plane ($6^{\circ}$ < l < $65^{\circ}$;$-1.5^{\circ}$ < b < $+1.5^{\circ}$) with the narrow band filter centered on the [Fe II] $1.64{\mu}m$ line using WFCAM at UKIRT. The observations will complement the UWISH2 survey, which have imaged the same area with the narrow band filter centered on the molecular hydrogen 1-0 S(1) emission line at $2.12{\mu}m$, and probe a dynamically active component of ISM. We present the goals and preliminary results of our survey.

• Bulletin of the Korean Space Science Society
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• 1993.10a
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• pp.18-18
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• 1993

According to the CCD photometric studies, the color distributions of globular clusters with collapsed cores, which are characterized by a power law cusp in thier surface brighness pronto, become bluer toward their centers, but this is not the case in the flat core clusters which are fit by the King model. To test the statistical implication of the color distribution within globular clusters, we built the sample dusters which follows the surface brightness pofile of the King model and power law cusp profile with the Sandage's standao luminosity function for M3 and the Salpter's initial mass functions. On the results from simulations based on the uniform random number generation the color gadients within globualr dusters mar be not likely to come from the statistical random distributions of stars but from the dynamical process on the cluster evolution.

• Journal of The Korean Astronomical Society
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• v.52 no.5
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• pp.145-158
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• 2019

We conducted a survey of open clusters within 1 kpc from the Sun using the astrometric and photometric data of the Gaia Data Release 2. We found 655 cluster candidates by visual inspection of the stellar distributions in proper motion space and spatial distributions in l - b space. All of the 655 cluster candidates have a well defined main-sequence except for two candidates if we consider that the main sequence of very young clusters is somewhat broad due to differential extinction. Cross-matching of our 653 open clusters with known open clusters in various catalogs resulted in 207 new open clusters. We present the physical properties of the newly discovered open clusters. The majority of the newly discovered open clusters are of young to intermediate age and have less than ~50 member stars.

• Journal of The Korean Astronomical Society
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• v.52 no.2
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• pp.41-47
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• 2019

We report on the timing properties of the 'Crab twin' pulsar PSR B0540-69 measured with X-ray data taken with the Swift telescope over a period of 1100 days. The braking index of the pulsar was estimated to be $n=0.03{\pm}0.013$ in a previous study performed in 2015 with 500-day Swift data. This small value of n is unusual for pulsars, and a comparison with an old estimate of $n{\approx}2.1$ for the same target determined ~10 years earlier suggests a dramatic change in the braking index. To confirm the small value and therefore the large change of n, we used 1100-day Swift observations including the data used in the earlier determination of n = 0.03. In this study we find that the braking index of PSR B0540-69 is $n=0.163{\pm}0.001$, somewhat larger than 0.03. Since the measured value of n is still much smaller than 2.1, we can confirm the dramatic change in the braking index for this pulsar.

• Journal of The Korean Astronomical Society
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• v.51 no.6
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• pp.171-183
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• 2018

To celebrate the tenth anniversary since the launch of Fermi Gamma-ray Space Telescope, we take a retrospect to a series of breakthroughs Fermi has contributed to pulsar astronomy in the last decade. Apart from significantly enlarging the population of ${\gamma}$-ray pulsars, observations with the Large Area Telescope onboard Fermi also show the population is not homogeneous. Instead, many classes and sub-classes have been revealed. In this paper, we will review the properties of different types of ${\gamma}$-ray pulsars, including radio-quiet ${\gamma}$-ray pulsars, millisecond pulsars, ${\gamma}$-ray binaries. Also, we will discuss the prospects of pulsar astronomy in the high energy regime.

• Proceedings of the Korea Contents Association Conference
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• 2019.05a
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• pp.49-50
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• 2019

2018년 11월 '리그 오브 레전드' S8 파이널 폐막식장에서 Riot Games회사는 홀로그래픽 기술을 이용하여 디지털 K/DA 걸 그룹과 리얼 걸 그룹 멤버들과 함께 K/DA의 데뷔 앨범 타이틀곡 'POP/STARS'를 제작하였다. 디지털 캐릭터는 VOCALOID 기술 및 창작자의 디자인에 기반을 두지만, 디지털콘텐츠로써의 가치는 UCC 컨버전스를 통해 기존 콘텐츠의 영역을 확장하여 디지털 캐릭터의 생명력과 활용성을 확대하였다. UCC에 기반을 둔 디지털 캐릭터는 주요한 정보 기여자와 소비자가 콘텐츠를 제작함으로써 그 영역이 확대되고 있다. 이에 본 연구에는 디지털 캐릭터 콘셉트를 이용한 K/DA 걸 그룹의 캐릭터의 특성을 살펴보고, UCC를 바탕으로 K/DA 걸 그룹 데뷔 이래 뉴스, OSMU의 특성, 디지털 캐릭터의 가용성을 중심으로 사용자의 캐릭터에 대한 역할을 분석하고자 한다.

• Journal of The Korean Astronomical Society
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• v.52 no.3
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• pp.83-88
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• 2019

Using ALMA observations of the $^{13}CN$ and DCN lines in the massive star-forming region G33.92+0.11A, we investigate the CN/HCN abundance ratio, which serves as a tracer of photodissociation chemistry, over the whole observed region. Even considering the uncertainties in calculating the abundance ratio, we find high ratios (${\gg}1$) in large parts of the source, especially in the outer regions of star-forming clumps A1, A2, and A5. Regions with high CN/HCN ratios coincide with the inflows of accreted gas suggested by Liu et al. (2015). We conclude that we found strong evidence for interaction between the dense gas clumps and the accreted ambient gas which may have sequentially triggered the star formation in these clumps.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.51.1-51.1
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• 2018

Based on the DOAO/eShels observations, we have derived radial velocity curves of the three Algol-type spectroscopic binary systems : Algol, ${\beta}$ Aur, and ${\varepsilon}$ Per. The radial velocity amplitudes of the primary and the secondary (K1 and K2) were consistent within a few % of the values from the previous studies. Mass ratios between the two stars that constitutes each system ranges ~1 to ~10. In addition to the orbital elements derived, we discuss about the spectroscopic ability of the DOAO/eShels instrument.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.47.2-47.2
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• 2019

We present a kinematic study of the two young OB associations Cygnus OB2 and Carina OB1 using the recently released Gaia astrometric data. The unimodal distributions of parallaxes of stars indicate that these associations are real stellar systems, rather than line-of-sight coincidences. The associations are found to comprise dense star clusters and a sparse halo which have different proper motions. Clusters have small spatial sizes with small dispersions in proper motion, while the haloes extending to tens of parsecs have a large dispersion in proper motion. We speculate that this aspect is related to that found in molecular clouds, the so-called "line width-size" relation. In this talk, the formation process of these associations is discussed, based on our findings.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.55.1-55.1
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• 2018

Theoretical models of reionization require that approximately 10% of the Lyman Continumm (LyC) photons escape from their host dark matter haloes and re-ionize neutral hydrogen in the Universe. However, observations of Lyman break galaxies (LBGs) at z~3 report much lower escape fractions of $f_{esc}{\sim}1%$. In an attempt to understand the discrepancy, we perform radiation-hydrodynamics simulations of isolated disk galaxies using RAMSES-RT with high resolution (maximum ~ 9 pc). We find that $f_{esc}$ is ~6% on average for the reference run ($Z=0.1Z{\odot}$), whereas the fraction decreases to ~1% in the case of metal-rich disk ($Z=1Z{\odot}$). This happens because dense metal-poor gas clumps are disrupted early due to strong Lya pressure and supernova explosions, while star particles are trapped for a longer period of time in the metal-rich environments. We also find that $f_{esc}$ is still significant (~4%) even when the amount of metal-poor gas is increased by a factor of 5. Our preliminary results suggest that the low escape fractions in LBGs may be better explained by (locally) metal-enriched gas near young stars than high gas fractions in galaxies.