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천문학논총 KCI 등재 Publications of the Korean Astronomical Society
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- 수록기간 1984 ~ 2024
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Volume 14 Issue 1 (1999년 6월) 6건
1.
1999.06
구독 인증기관 무료, 개인회원 유료
We performed VRI CCD surface photometry of three spiral galaxies of HCG10 in order to understand the effect of interactions in the compact group. The morphology of the largest member NGC 536 seems to be normal but its bulge is thought to be of an oblate spheroid. The central surface brightness of the disk of NGC 536 is much fainter than that of disks of nearby spiral galaxies. The morphologies of NGC 531 and NGG 542 appear to be affected by interactions which lead to a warped disk in NGC 531 and a slightly bent disk in NGC 542. NGC 531 have a boxy bulge and a Freeman Type II disk both of which strongly suggest the presence of a bar in the galaxy. There is a break in the slope of the luminosity profile of NGC 542 which is dominated by the disk component.
4,000원
2.
1999.06
구독 인증기관 무료, 개인회원 유료
Current searches for gravitational microlensing events are being carried out only by a photometric method. In this review paper, we demonstrate that the nature of Galactic lenses can be significantly better constrained with the additional astrometric observations of microlensng events. First, by astromerically observing lensing events, one can resolve the lens parameter degeneracy, and thus the lens mass can be determined with improved precision. Second, by being free from the blending problem, astrometric observations of lensing events will allow one to improve the uncertainties in the determined Einstein time scales. Third, the lens brightness, which could not be measured photometrically, can be measured from the astrometric observations of lensing events, and thus the nature of lens matter can be better constrained. Finally, with the help of astrometric followup observations of a binary-lens event, one can uniquely determine the solution of lens parameters, allowing one to obtain important astronomical information about the source star and the lens itself.
4,600원
3.
1999.06
구독 인증기관 무료, 개인회원 유료
We have developed a Monte Carlo code, which solves the problem of radiative transfer in anisotropically scattering atmosphere. The radiative code is flexible in handlings of the system geometry, the distribution of scattering particles, and the source-particle geometry. This code treats the case of highly forward throwing scattering. As performance tests, we have compared the result of Monte Carlo calculations with that of Quasi-Diffusion method for a spherically symmetric cloud model.
4,000원
4.
1999.06
구독 인증기관 무료, 개인회원 유료
We have constructed a synthetic spectrum of the 2.5 micron C2H C2H bands and compared them with diminutive structures in the near-infrared spectra of Comets P/Halley and West (1976 VI). We found that the Q branches of the C2H C2H bands coincide with two small emission peaks in the spectra of the comets. We undertook Monte Carlo simulations using observed emission intensities of C2 C2 and possibly C2H C2H in Comet P/Halley in order to derive a lifetime range of C2H C2H and a production rate at the time of observations of P/Halley. We obtained a C2H C2H production rate of 1×1027sec−1 1×1027sec−1 for P/Halley on December 20, 1985, assuming the 2.5 micron features are due to C2H C2H . We derived a very short lifetime (<100 seconds) of C2H C2H at 1AU heliocentric distance, assuming that the only parent molecule for C2H C2H and C2 C2 is C2H C2H . Using this short lifetime we were unable to fit our C2 C2 distribution model to C2 C2 distribution curves observed by O'Dell et al.(1988), because our curve shows a steep slope compared with the observed one. We conclude that there must be significant additional source(s) for C2H C2H and C2 C2 other than C2H2 C2H2 .
4,000원
5.
1999.06
구독 인증기관 무료, 개인회원 유료
We have carried out measurements of 1.2-1.6GHz radio interferences around Seoul Radio Astronomy Observatory located in the campus of Seoul National University. We received interference signals using a pyramidal horn antenna and measured its power using a spectrum analyzer with 1MHz resolution after ~60dB amplification. In order to check the spatial characteristics, we made observations at every 30∘ 30∘ in azimuth at elevation of 30∘and60∘ 30∘and60∘ . Also, in order to check the temporal characteristics, we repeated the all-sky observations five times at every six hours. The results may be summarized as follows: (1) There are strong (≥−20dBm) (≥−20dBm) interferences between 1.2 and 1.4GHz. Particularly strong interferences are observed at 1.271 and 1.281GHz, which have maximum powers of -0.34dBm and -0.56dBm, respectively. (2) The characteristics of the interferences do not depend strongly on directions, although the interferences are in general weak at high elevation and in east-west direction. (3) The interferences appear for a very short (≤0.01s) (≤0.01s) period of time, so that the average power is much smaller than the maximum power. Strong interferences with large (≤−49.0dBm) (≤−49.0dBm) average power have been observed at 1.271, 1.281, 1.339, and 1.576GHz. At these frequencies, the interferences appear repeatedly with a period of ≤0.1s ≤0.1s By analyzing the observed power, we find that, for the strongest 1.271GHz interference, the average intensity is −171dBW/m2/Hz −171dBW/m2/Hz and that the maximum intensity is −122dBW/m2/Hz −122dBW/m2/Hz . If this interference is delivered to the detector without any shielding, then its power would be much greater than the rms noise of a typical line spectrum. Therefore, it is important to shield all the parts of receiver carefully from radio interferences. Also, without appropriate shielding, the sensitivity of a receiver could be limited by the interference.
4,000원
6.
1999.06
구독 인증기관 무료, 개인회원 유료
We have improved the control and driving system of 16' reflector at Kwanak Observatory at Seoul National University, by completing encoder unit, and by developing programs for correction of errors resulting from hardware defects. The hardware defects of this telescope system are the large backlash and the nonuniform tracking and pointing. The telescope pointing accuracy for RA is improved to a few arc minutes, and that for DEC is several tens of arc minutes. The guiding error is improved to 0.7 arcsec/minute, allowing up to 3 minutes exposure for CCD imaging under typical seeing conditions at the Observatory.
4,000원
