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1968년 ~ 2024년까지 1,211 건의 한국천문학회지를 격월간 확인하실 수 있습니다.
- The Korean Astronomical Society (The Korean Astronomical Society)
- 계간 (Quarterly)
- ISSN : 1225-4614 (ISSN : 1225-4614)
1225-4614
- DB구축현황 : 1,211건 (DB Construction : 1,211 Articles)
총 게시글 1,211건
페이지 6/122
51
- Jeon, Junhyeok
- Journal of the Korean astronomical society = 천문학회지
- 55, n.4
- pp.99-110
- 2022
- 원문 바로보기
This study presents the characteristics of publications in the Journal of Korean Astronomy Society (JKAS) from 1968 to 2021. JKAS has published 763 research articles over the past 54 years. In addition, 376 proceedings were also published with research articles. There were slight increases and decreases in the number of articles published in JKAS in the 1990s and 2000s, and in 2015 there was the highest recorded number of articles published for a given year. Since then, the number of articles has tended to decrease each year, up to and including the most recent period (2020-2021), which includes the Coronavirus pandemic. However, since theory centered research is primarily conducted without being swayed by society and policies, and that the proportion of authors belonging to educational institutions, such as universities, is high, the future direction of JKAS is encouraging. There are also positive developments including sustained researchers affiliated with international institutions at greater than approximately 23%, as well as improvements in the impact factor. Therefore, it is important to not be deterred by the decreasing trends of the quantitative aspect, but to respond positively by determining a future roadmap.
52
- Tetsuya, Magara
- Journal of the Korean astronomical society = 천문학회지
- 55, n.6
- pp.215-220
- 2022
- 원문 바로보기
To seek an atmospheric heating mechanism operating on the Sun we investigated a heating source generated by a downflow, both of which may arise in a magnetic loop dynamically formed on the Sun via flux emergence. Since an observation shows that the illumination of evolving magnetic loops under the dynamic formation occurs sporadically and intermittently, we performed a magnetohydrodynamic simulation of flux emergence to obtain a high-cadence simulated data, where temperature enhancement was identified at the footpoint of an evolving magnetic loop. Unlike a rigid magnetic loop with a confined flow in it, the evolving loop in a low plasma β atmosphere is subjected to local compression by the magnetic field surrounding the loop, which drives a strong supersonic downflow generating an effective footpoint heating source in it. This may introduce an energy conversion system to the magnetized atmosphere of the Sun, in which the free magnetic energy causing the compression via Lorentz force is converted to the flow energy, and eventually reduced to the thermal energy. Dynamic and thermodynamic states involved in the system are explained.
53
- Park, Woojin
- Journal of the Korean astronomical society = 천문학회지
- 55, n.1
- pp.11-22
- 2022
- 원문 바로보기
We introduce the Transformable Reflective Telescope (TRT) kit that applies an aluminum profile as a base plate for precise, stable, and lightweight optical system. It has been utilized for optical surface measurements, developing alignment and baffle systems, observing celestial objects, and various educational purposes through Research & Education projects. We upgraded the TRT kit using the aluminum profile and truss and isogrid structures for a high-end optical test device that can be used for prototyping of precision telescopes or satellite optical systems. Thanks to the substantial aluminum profile and lightweight design, mechanical deformation by self-weight is reduced to maximum 67.5 ㎛, which is an acceptable misalignment error compared to its tolerance limits. From the analysis results of non-linear vibration simulations, we have verified that the kit survives in harsh vibration environments. The primary mirror and secondary mirror modules are precisely aligned within 50 ㎛ positioning error using the high accuracy surface finished aluminum profile and optomechanical parts. The cross laser module helps to align the secondary mirror to fine-tune the optical system. The TRT kit with the precision aluminum mirror guarantees high quality optical performance of 5.53 ㎛ Full Width at Half Maximum (FWHM) at the field center.
54
- Kim, Minsu
- Journal of the Korean astronomical society = 천문학회지
- 55, n.5
- pp.149-172
- 2022
- 원문 바로보기
We present a new method which constructs an Hɪ super-profile of a galaxy which is based on profile decomposition analysis. The decomposed velocity profiles of an Hɪ data cube with an optimal number of Gaussian components are co-added after being aligned in velocity with respect to their centroid velocities. This is compared to the previous approach where no prior profile decomposition is made for the velocity profiles being stacked. The S/N improved super-profile is useful for deriving the galaxy's global Hɪ properties like velocity dispersion and mass from observations which do not provide sufficient surface brightness sensitivity for the galaxy. As a practical test, we apply our new method to 64 high-resolution Hɪ data cubes of nearby galaxies in the local Universe which are taken from THINGS and LITTLE THINGS. In addition, we also construct two additional Hɪ super-profiles of the sample galaxies using symmetric and all velocity profiles of the cubes whose centroid velocities are determined from Hermite h3 polynomial fitting, respectively. We find that the Hɪ super-profiles constructed using the new method have narrower cores and broader wings in shape than the other two super-profiles. This is mainly due to the effect of either asymmetric velocity profiles' central velocity bias or the removal of asymmetric velocity profiles in the previous methods on the resulting Hɪ super-profiles. We discuss how the shapes (𝜎<sub>n</sub>/𝜎<sub>b</sub>, A<sub>n</sub>/A<sub>b</sub>, and A<sub>n</sub>/A<sub>tot</sub>) of the new Hɪ super-profiles which are measured from a double Gaussian fit are correlated with star formation rates of the sample galaxies and are compared with those of the other two super-profiles.
55
- Chung, Sun-Ju
- Journal of the Korean astronomical society = 천문학회지
- 55, n.4
- pp.123-130
- 2022
- 원문 바로보기
We present the analysis of a planetary microlensing event OGLE-2019-BLG-0362 with a shortduration anomaly (~0.4 days) near the peak of the light curve, which is caused by the resonant caustic. The event has a severe degeneracy with ∆𝜒<sup>2</sup> = 0.9 between the close and the wide binary lens models both with planet-host mass ratio q ≃ 0.007. We measure the angular Einstein radius but not the microlens parallax, and thus we perform a Bayesian analysis to estimate the physical parameters of the lens. We find that the OGLE-2019-BLG-0362L system is a super-Jovian-mass planet <TEX>$M_p=3.26^{+0.83}_{-0.58}M_J $</TEX> orbiting an M dwarf <TEX>$M_h=0.42^{+0.34}_{-0.23}M_{\odot}$</TEX> at a distance <TEX>$D_L=5.83^{+1.04}_{-1.55}kpc$</TEX>. The projected star-planet separation is <TEX>${\alpha}_{\bot}= 2.18^{+0.58}_{-0.72}AU$</TEX>, which indicates that the planet lies beyond the snow line of the host star.
56
- Naeun, Shin
- Journal of the Korean astronomical society = 천문학회지
- 55, n.6
- pp.207-213
- 2022
- 원문 바로보기
The Seoul Radio Astronomy Observatory (SRAO) operates a 6.1-meter radio telescope on the Gwanak campus of Seoul National University. We present the efforts to reform SRAO to a Very Long Baseline Interferometry (VLBI) station, motivated by recent achievements by millimeter interferometer networks such as Event Horizon Telescope, East Asia VLBI Network, and Korean VLBI Network (KVN). For this goal, we installed a receiver that had been used in the Combined Array for Research in Millimeter-wave Astronomy and a digital backend, including an H-maser clock. The existing hardware and software were also revised, which had been dedicated only to single-dish operations. After several years of preparations and test observations in 1 and 3-millimeter bands, a fringe was successfully detected toward 3C 84 in 86 GHz in June 2022 for a baseline between SRAO and KVN Ulsan station separated by 300 km. Thanks to the dual frequency operation of the receiver, the VLBI observations will soon be extended to the 1 mm band and verify the frequency phase referencing technique between 1 and 3-millimeter bands.
57
- Kim, Sungsoo S.
- Journal of the Korean astronomical society = 천문학회지
- 55, n.3
- pp.75-86
- 2022
- 원문 바로보기
The lunar surface progressively darkens and reddens as a result of sputtering from solar wind particles and bombardment of micrometeoroids. The extent of exposure to these space weathering agents is frequently calculated as the location in a diagram of reflectance at 750 nm vs. 950 nm/750 nm color (R-C). Sim & Kim (2018) examined the R-C trends of pixels within ~3,500 craters, and revealed that the length (L) and skewness (s) of R-C trends can be employed as a secondary age or maturity indicator. We broaden this research to general lunar surface areas (3,400 tiles of 0.25° × 0.25° size) in 218 mare basalt units, whose ages have been derived from the size-frequency distribution analysis by Hiesinger et al. (2011). We discover that L and s rise with age until ~3.2 Gyr and reduce rather rapidly afterward, while the optical maturity, OMAT, reduces monotonically with time. We show that in some situations, when not only OMAT but also L and s are incorporated in the estimation utilizing 750 & 950 nm photometry, the age estimation becomes considerably more reliable. We also observed that OMAT and the lunar cratering chronology function (cumulative number of craters larger than a certain diameter as a function of time) have a relatively linear relationship.
58
- Jeon, Seong-Gyeong
- Journal of the Korean astronomical society = 천문학회지
- 55, n.3
- pp.67-74
- 2022
- 원문 바로보기
In this study, we perform a statistical investigation of the kinematic classification of 4,264 coronal mass ejections (CMEs) from 1996 to 2015 observed by SOHO/LASCO C3. Using the constant acceleration model, we classify these CMEs into three groups: deceleration, constant velocity, and acceleration motion. For this, we devise three different classification methods using fractional speed variation, height contribution, and visual inspection. The main results of this study can be summarized as follows. First, the fractions of three groups depend on the method used. Second, about half of the events belong to the groups of acceleration and deceleration. Third, the fractions of three motion groups as a function of CME speed are consistent with one another. Fourth, the fraction of acceleration motion decreases as CME speed increases, while the fractions of other motions increase with speed. In addition, the acceleration motions are dominant in low speed CMEs whereas the constant velocity motions are dominant in high speed CMEs.
59
- Chang, Heon-Young
- Journal of the Korean astronomical society = 천문학회지
- 55, n.5
- pp.139-148
- 2022
- 원문 바로보기
We explore the latitudinal distribution of sunspots and pursue to establish a correlation between the statistical parameters of the latitudinal distribution of sunspots and characteristics of solar activity. For this purpose, we have statistically analyzed the daily sunspot areas and latitudes observed from May in 1874 to September in 2016. As results, we confirm that the maximum of the monthly averaged International Sunspot Number (ISN) strongly correlates with the mean number of sunspots per day, while the maximum ISN strongly anti-correlates with the number of spotless days. We find that both the maximum ISN and the mean number of sunspots per day strongly correlate with the the average latitude, the standard deviation, the skewness of the the latitudinal distribution of sunspots, while they appears to marginally correlate with the kurtosis. It is also found that the northern and southern hemispheres seem to show a correlated behavior in a different way when sunspots appearing in the northern and southern hemispheres are examined separately.
60
- Kim, Jinkyu
- Journal of the Korean astronomical society = 천문학회지
- 55, n.4
- pp.87-97
- 2022
- 원문 바로보기
Polarimetric measurements of the lunar surface from lunar orbit soon will be available via Wide-Field Polarimetric Camera (PolCam) onboard the Korea Pathfinder Lunar Orbiter (KPLO), which is planned to be launched in mid 2022. To provide calibration data for the PolCam, we are conducting speckle polarimetric measurements of the nearside of the Moon from the Earth's ground. It appears that speckle imaging of the Moon for scientific purposes has not been attempted before, and there is need for a procedure to create a 'lucky image' from a number of observed speckle images. As a first step of obtaining calibration data for the PolCam from the ground, we search for the best sharpness measure for lunar surfaces. We then calculate the minimum number of speckle images and the number of images to be shift-and-added for higher resolution (sharpness) and signal-to-noise ratio.