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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 48/122
471
- OHASHI NAGAYOSHI
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.103-106
- 2005
- 원문 바로보기
The Submillimeter Array (SMA), a collaborative project of the Smithsonian Astrophysical Observatory (SAO) and the Academia Sinica Institute of Astronomy & Astrophysics (ASIAA), has begun operation on Mauna Kea in Hawaii. A total of eight 6-m radio telescopes comprise the array with currently working receiver bands at 230, 345, and 690 GHz. The array will have 8 receiver bands covering the frequency range of 180-900 GHz. The backend is flexible analog-digital correlator with a full bandwidth of 2GHz, which is very powerful to cover several line emissions simultaneously. The current status and future plans of the SMA are described with emphasis on Taiwanese efforts.
472
- YUAN CHI
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.337-338
- 2005
- 원문 바로보기
This is to summarize a joint discussion on the future of EAMA in EAMA6. The emphasis was placed on the near future instead of the distant future, Formation of the Working Groups as a means to carry the cooperation for the regions was generally agreed by the attendants of EAMA6 to be the best way toward the establishment of future East Asian Observatory (EAO). Association of Core Observatories (ACO) was proposed to bring resources and foster joint projects for EAMA activities.
473
- CHEN ALFRED BING-CHIH
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.303-306
- 2005
- 원문 바로보기
Transient luminous events (TLEs; sprites, elves, jets and etc.) are lightning-related optical flashes occurring above thunderstorms. Since the first discovery of sprites in 1989, scientists have learned a great deal about the morphological, spectroscopic and electromagnetic characteristics of TLEs through ground and spacecraft campaigns. However, most of the TLE studies were based on events recorded over US High Plains. To elucidate the possible biasing effects, space-borne observations are needed and have their merits. Imager of sprites and Upper Atmospheric Lightning (ISUAL) on the FORMOSAT-2 satellite is the first instrument to carry out a true global measurement of TLEs from a low- earth orbit. In this short paper, we apply a common astronomical data analysis technique, two-color diagram, on the ISUAL spectrophotometer (SP) data. By choosing appropriated bandpasses and converting the measured flux of TLEs into the unit of magnitude, two-color diagrams of TLEs can be constructed. We demonstrate that two-color diagrams, which were constructed from the narrow-band spectrophotometer data, can be used to classify different types of TLEs and trace their temporal evolution. The amount of reddening due to Earth's atmosphere can also be estimated from two-color diagrams assembled from the broad-band spectrophotometer data.
474
- ARDI ELIANI
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.207-210
- 2005
- 원문 바로보기
We study the influence of rotation on the dynamical evolution of collisional single-mass stellar clusters up to core-collapse by using N-body simulations. Rotating King models which are characterized by dimensionless central potential parameter <TEX>$W_o$</TEX> and the rotation parameter <TEX>$W_o$</TEX> are used as initial models. Our results show that inner shells slowly contract until core-collapse phase is reached, followed by a slow expansion. Angular momentum is transported outward, while the core is rotating even faster than before, as predicted by gravogyro catastrophe theory. We confirm that rotation plays an important role in accelerating the dynamical evolution of stellar cluster, in particular in accelerating the core collapse.
475
- KIM TAEHYUN
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.145-148
- 2005
- 원문 바로보기
We present a photometric study of galaxies in the central regions of six nearby galaxy clusters at redshift z=0.0231<TEX>${\~}$</TEX>0.0951. We have derived BVI photometry of the galaxies from the CCD images obtained at the Bohyunsan Optical Astronomical Observatory (BOAO) in Korea, and JHKs photometry of the bright galaxies from the 2MASS extended source catalog. Comparing the galaxy photometry results with the simple stellar population model of Bruzual & Charlot (2003) in the optical & NIR color-color diagrams, we have estimated the ages and metallicities of early type galaxies. We have found that the observed galaxies had recent star-formation mostly 5 <TEX>${\~}$</TEX> 7 Gyrs ago but the spread in age estimation is rather large. The average metallicities are [Fe/H]=0.l<TEX>${\~}$</TEX>0.5 dex. These results support the hypothesis that large early type galaxies in clusters are formed via hierarchical merging of smaller galaxies.
476
- NOUMARU JUNICHI
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.101-102
- 2005
- 원문 바로보기
Subaru Telescope proposes to hold Subaru East Asia Youth School (Tentative Name) in 2005.
477
- HIRANO NAOMI
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.219-222
- 2005
- 원문 바로보기
We present the high-resolution (2'-4') images of the molecular envelopes surrounding the evolved stars, V Hya, VY CMa, and <TEX>${\pi}^1$</TEX> Gru observed with the Submillimeter Array. The CO J=2-1 and 3-2 images of the carbon star V Hya show that the circumstellar structure of this star consists of three kinematic components; there is a flattened disk-like envelope that is expanding with a velocity of <TEX>${\~}16 km\;s^{-1}$</TEX>, the second component is the medium-velocity wind having a deprojected velocity of 40-120 km <TEX>$s^{-l}$</TEX> moving along the disk plane, and the third one is the bipolar molecular jet having an extreme velocity of 70-185 km <TEX>$s^{-l}$</TEX>. The axis of this high velocity jet is perpendicular to the plane of the disk-like envelope. We found that the circumstellar structure of the S-star <TEX>${\pi}^1$</TEX> Gru traced by the CO J =2-1 resembles that of V Hya quite closely; the star is surrounded by the expanding disk-like envelope and is driving the medium-velocity wind along the disk plane. We also obtained the excellent images of VY CMa with the CO and <TEX>$^{13}CO$</TEX> J=2-1 and <TEX>$SO\;6_5-5_4$</TEX> lines. The maps of three molecular lines show that the envelope has a significant velocity gradient in the east-west direction, suggesting that the envelope surrounding VY CMa is also flattened and expanding along its radial direction. The high-resolution images obtained with the SMA show that some AGB stars are associated with the asymmetric mass loss including the equatorial wind and bipolar jet.
478
- LIM JEREMY
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.237-240
- 2005
- 원문 바로보기
We present images of L1551 IRS5 at angular resolutions as high as <TEX>${\~}$</TEX>30 mas, corresponding to a spatial resolution of <TEX>${\~}$</TEX>5 AU, made at 7 mm with the VLA. Previously known to be a binary protostellar system, we show that L1551 IRS5 is likely a triple protostellar system. The primary and secondary components have a projected separation of <TEX>${\~}$</TEX>46 AU, whereas the tertiary component has a projected separation of <TEX>${\~}$</TEX>11 AU from the primary component. The circumstellar dust disks of the primary and secondary components have dimensions of <TEX>${\~}$</TEX>15 AU, whereas that of the tertiary component has a dimension of <TEX>${\~}$</TEX>10 AU. Their major axes are closely, but not perfectly, aligned with each other, as well as the major axis of the surrounding flattened, rotating, and contracting molecular condensation (pseudodisk). Furthermore, the orbital motion of the primary and secondary components is in the same direction as the rotational motion of this pseudodisk. We suggest that all three protostellar components formed as a result of the fragmentation of the central region of the molecular pseudo disk. The primary and secondary components, but apparently not the tertiary component, each exhibits a bipolar ionized jet that is centered on and which emergers perpendicular to its associated dust disk. Neither jets are resolved along their base, implying that they are driven within a radial distance of <TEX>${\~}$</TEX>2.5 AU from their central protostars. Finally, we show evidence for what may be dusty matter streams feeding the two main protostellar components.
479
- SHEN ZHI-QIANG
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.261-266
- 2005
- 원문 바로보기
This paper reviews the progress in the VLBI (Very Long Baseline Interferometry) studies of Sgr A<TEX>$\ast$</TEX>, the best known supermassive black hole candidates with a dark mass concentration of <TEX>$4 {\times} 10^6 M_{\bigodot}$</TEX> at the center of the Milky Way. The emphasis is on the importance of the millimeter and sub-millimeter VLBI observations in the detection of Sgr A<TEX>$\ast$</TEX>'s intrinsic structure and search for the structural variation.
480
- Bong, Su-Chan
- Journal of the Korean astronomical society = 천문학회지
- 38, n.4
- pp.445-462
- 2005
- 원문 바로보기
In a companion paper, we have presented so-called Spatio-Spectral Maximum Entropy Method (SSMEM) particularly designed for Fourier-Transform imaging over a wide spectral range. The SSMEM allows simultaneous acquisition of both spectral and spatial information and we consider it most suitable for imaging spectroscopy of solar microwave emission. In this paper, we run the SSMEM for a realistic model of solar microwave radiation and a model array resembling the Owens Valley Solar Array in order to identify and resolve possible issues in the application of the SSMEM to solar microwave imaging spectroscopy. We mainly concern ourselves with issues as to how the frequency dependent noise in the data and frequency-dependent variations of source size and background flux will affect the result of imaging spectroscopy under the SSMEM. We also test the capability of the SSMEM against other conventional techniques, CLEAN and MEM.