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- The Korean Space Science Society (The Korean Astronomical Society)
- 계간 (Quarterly)
- ISSN : 1225-052x (ISSN : 1225-052x)
1225-052x
- DB구축현황 : 1,252건 (DB Construction : 1,252 Articles)
총 게시글 1,252건
페이지 42/126
411
- Sohn, Dong-Hyo
- Journal of astronomy and space sciences
- 29, n.1
- pp.1-10
- 2012
- 원문 바로보기
In this study, global positioning system (GPS)-derived precipitable water vapor (PWV) and microwave radiometer (MWR)-measured integrated water vapor (IWV) were compared and their characteristics were analyzed. Comparing those two quantities for two years from August 2009, we found that GPS PWV estimates were larger than MWR IWV. The average difference over the entire test period was 1.1 mm and the standard deviation was 1.2 mm. When the discrepancies between GPS PWV and MWR IWV were analyzed depending on season, the average difference was 0.7 mm and 1.9 mm in the winter and summer months, respectively. Thus, the average difference was about 2.5 times larger in summer than that in winter. However, MWR IWV measurements in the winter months were over-estimated than those in the summer months as the water vapor content got larger. The results of the diurnal analysis showed that MWR IWV was underestimated in the daytime, showing a difference of 0.8 mm. In the early morning hours, MWR IWV has a tendency to be over-estimated, with a difference of 1.3 mm with respect to GPS PWV.
412
- Sanborn, Jason J.
- Journal of astronomy and space sciences
- 29, n.1
- pp.63-67
- 2012
- 원문 바로보기
Observations with milliarsecond resolution using the Navy Optical Interferometer have been obtained for a number of stellar systems which include high-mass binaries, eclipsing binaries, and radio stars. These observations also reveal the previously unseen companions in single-lined spectroscopic binaries via directly measured flux ratios. We will present examples of published and ongoing research efforts of these systems to illustrate how an optical interferometer contributes to our knowledge of stars, their environment, and companions. These studies include a conclusive revealing of the previously unseen companion in the single-lined binary <TEX>${\Phi}$</TEX> Herculis, the direct determination of orbital parameters in the wide and close orbits of Algol, and revealing the orbit of <TEX>${\beta}$</TEX> Lyrae with spatially resolved images of the <TEX>$H{\alpha}$</TEX> emission.
413
- Linnell, Albert P.
- Journal of astronomy and space sciences
- 29, n.2
- pp.123-129
- 2012
- 원문 바로보기
The BINSYN program package, recently expanded to calculate synthetic spectra of cataclysmic variables, is being further extended to include synthetic photometry of ordinary binary stars in addition to binary stars with optically thick accretion disks. The package includes a capability for differentials correction optimization of eclipsing binary systems using synthetic photometry.
414
- Hwang, Junga
- Journal of astronomy and space sciences
- 29, n.4
- pp.329-336
- 2012
- 원문 바로보기
Korea Astronomy and Space Science Institute researchers have installed and operated magnetometers at Bohyunsan Observatory to measure the Earth's magnetic field variations in South Korea. In 2007, we installed a fluxgate magnetometer (RFP-523C) to measure H, D, and Z components of the geomagnetic field. In addition, in 2009, we installed a Overhauser proton sensor to measure the absolute total magnetic field F and a three-axis magneto-impedance sensor for spectrum analysis. Currently three types of magnetometer data have been accumulated. In this paper, we use the H, D, Z components of fluxgate magnetometer data to investigate the characteristics of mid-latitude geomagnetic field variation. To remove the temporary changes in Earth's geomagnetic filed by space weather, we use the international quiet days' data only. In other words, we performed a superposed epoch analysis using five days per each month during 2008-2011. We find that daily variations of H, D, and Z shows similar tendency compared to previous results using all days. That is, H, D, Z all three components' quiet intervals terminate near the sunrise and shows maximum 2-3 hours after the culmination and the quiet interval start from near the sunset. Seasonal variations show similar dependences to the Sun. As it becomes hot season, the geomagnetic field variation's amplitude becomes large and the quiet interval becomes shortened. It is well-known that these variations are effects of Sq current system in the Earth's atmosphere. We confirm that the typical mid-latitude geomagnetic field variations due to the Sq current system by excluding all possible association with the space weather.
415
- Lee, Yong-Sam
- Journal of astronomy and space sciences
- 29, n.2
- pp.221-232
- 2012
- 원문 바로보기
We analyzed the manufacturing procedure, specifications, repair history, and details of celestial movements of the water-hammering type <TEX>$Honsang$</TEX> (celestial globe). Results from our study on the remaining <TEX>$Honsangs$</TEX> in China and Japan and on the reconstruction models in Korea were applied to our conceptual design of the water-hammering type <TEX>$Honsang$</TEX>. A <TEX>$Honui$</TEX> (armillary sphere) and <TEX>$Honsang$</TEX> using the water-hammering method were manufactured in <TEX>$Joseon$</TEX> in 1435 (the 17th year of King <TEX>$Sejong$</TEX>). <TEX>$Jang$</TEX> <TEX>$Yeong-Sil$</TEX> developed the <TEX>$Honsang$</TEX> system based on the water-operation method of <TEX>$Shui$</TEX> <TEX>$y{\ddot{u}}n$</TEX> <TEX>$i$</TEX> <TEX>$hsiang$</TEX> <TEX>$t'ai$</TEX> in China. Water-operation means driving water wheels using a water flow. The most important factor in this type of operation is the precision of the water clock and the control of the water wheel movement. The water-hammering type <TEX>$Honsang$</TEX> in <TEX>$Joseon$</TEX> probably adopted the <TEX>$Cheonhyeong$</TEX> (天衡; oriental escapement device) system of <TEX>$Shui$</TEX> <TEX>$y{\ddot{u}}n$</TEX> <TEX>$i$</TEX> <TEX>$hsiang$</TEX> <TEX>$t'ai$</TEX> in China and the overflow mechanism of <TEX>$Jagyeongnu$</TEX> (striking clepsydra) in <TEX>$Joseon$</TEX>, etc. In addition to the <TEX>$Cheonryun$</TEX> system, more gear instruments were needed to stage the rotation of the <TEX>$Honsang$</TEX> globe and the sun's movement. In this study, the water-hammering mechanism is analyzed in the structure of a water clock, a water wheel, the <TEX>$Cheonhyeong$</TEX> system, and the <TEX>$Giryun$</TEX> system, as an organically working operation mechanism. We expect that this study will serve as an essential basis for studies on <TEX>$Heumgyeonggaknu$</TEX>, the water-operating astronomical clock, and other astronomical clocks in the middle and latter parts of the <TEX>$Joseon$</TEX> dynasty.
416
- Yoon, Joh-Na
- Journal of astronomy and space sciences
- 29, n.4
- pp.397-405
- 2012
- 원문 바로보기
Astronomical Observations at Chungbuk National University Observatory (CBNUO) with an 1 m telescope have begun since April 2008, and Near-Earth Space Survey observations also have been started since November 2010, with a 0.6 m wide field telescope developed by Korea Astronomy and Space Science Institute. To improve observational efficiency, we developed a weather monitoring system enabling automatic monitoring for the weather conditions and checking the status of the observational circumstances, such as dome status. We hope this weather monitoring system can be helpful to more than 100 Korean domestic observatories, including public outreach facilities. In this paper, we present the statistic analysis of the weather conditions collected at CBNUO for 3 years (2009- 2011) and comparisons were made for clear nights between using only humidity data and both humidity and cloud data.
417
- Kim, Eojin
- Journal of astronomy and space sciences
- 29, n.4
- pp.337-342
- 2012
- 원문 바로보기
In this study, the transient second or third layer on the topside of the Martian ionosphere were investigated with the most recently released Mars advanced radar for subsurface and ionospheric sounding/Mars Express data obtained from January 2010 to September 2011 to study the correlation between these topside additional layers and surface magnetic fields, solar zenith angle and solar activities. When examining the zones where the topside layer appeared, the occurrence rate of the topside layer was low at the areas with a strong Martian crustal magnetic field as observed by the Mars global surveyor. The occurrence rate of additional layers on the Martian topside ionosphere decreases as the solar zenith angle increases. However, these layers appeared significantly near the terminator of which solar zenith angle is <TEX>$90^{\circ}$</TEX>. In comparison between F10.7 which is the index of solar activities and the occurrence rate of the topside layer by date, its occurrence rate was higher in 2011 than in 2010 with less solar activities. The result of this study will contribute to better understanding of the environments in the topside of the ionosphere through the correlation between the various conditions regarding the Martian ionosphere and the transient layer.
418
- Kafka, Stella
- Journal of astronomy and space sciences
- 29, n.2
- pp.163-167
- 2012
- 원문 바로보기
Although the identification of the progenitors of type Ia supernovae (SNeIa) remains controversial, it is generally accepted that they originate from binary star systems in which at least one component is a carbon-oxygen white dwarf (WD); those systems are grouped under the wide umbrella of cataclysmic variables. Current theories for SNeIa progenitors hold that, either via Roche lobe overflow of the companion or via a wind, the WD accumulates hydrogen or helium rich material which is then burned to C and O onto the WD's surface. However, the specifics of this scenario are far from being understood or defined, allowing for a wealth of theories fighting for attention and a dearth of observations to support them. I discuss the latest attempts to identify and study those controversial SNeIa progenitors. I also introduce the most promising progenitor in hand and I present observational diagnostics that can reveal more members of the category.
419
- Park, Chang-Geun
- Journal of astronomy and space sciences
- 29, n.3
- pp.295-303
- 2012
- 원문 바로보기
In this study, we compared the precipitable water vapor (PWV) data derived from the radiosonde observation data at Sokcho Observatory and the PWV data at Sokcho Global Positioning System (GPS) Observatory provided by Korea Astronomy and Space Science Institute, for the years of 2006, 2008, 2010, and analyzed the radiosonde seasonal, diurnal bias according to radiosonde sensor types. In the scatter diagram of the daytime and nighttime radiosonde PWV data and the GPS PWV data, dry bias was found in the daytime radiosonde observation as known in the previous study. Overall, the tendency that the wet bias of the radiosonde PWV increased as the GPS PWV decreased and the dry bias of the radiosonde PWV increased as the GPS PWV increased. The quantitative analysis of the bias and error of the radiosonde PWV data showed that the mean bias decreased in the nighttime except for 2006 winter, and in comparison for summer, RS92-SGP sensor showed the highest quality.
420
- Sion, Edward M.
- Journal of astronomy and space sciences
- 29, n.2
- pp.169-173
- 2012
- 원문 바로보기
A summary is presented of what is currently known about the surface temperatures of accreting white dwarfs (WDs) detected in non-magnetic and magnetic cataclysmic variables (CVs) based upon synthetic spectral analyses of far ultraviolet data. A special focus is placed on WD temperatures above and below the CV period gap as a function of the orbital period, <TEX>$P_{orb}$</TEX>. The principal uncertainty of the temperatures for the CV WDs in the <TEX>$T_{eff}-P_{orb}$</TEX> distribution, besides the distance to the CV, is the mass of the WD. Only in eclipsing CV systems, an area of eclipsing binary studies, which was so central to Robert H. Koch's career, is it possible to know CV WD masses with high precision.