간행물
천문학논총 KCI 등재 Publications of the Korean Astronomical Society
- 발행기관 한국천문학회
- 자료유형 학술지
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- 수록기간 1984 ~ 2024
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권호리스트/논문검색
Volume 10 (1995년 12월) 10건
1.
1995.12
구독 인증기관 무료, 개인회원 유료
We observed impact spots on Jupiter which were formed by the collision with fragments of Shoemaker-Levy 9 comet during the period from 17 July to 13 August, by using the SNU 61cm reflector combined with CCD camera and DBVRI filters. In order to get more clear image of impact spots, the observed data were processed by the unsharp masking method, high-pass filtering method and Richardson-Lucy algorithm after the basic processing through IRAF package. The sizes of impact spots range from 2000km to 1000km, and from this size, the original size of comet fragments before collision with Jupiter is estimated to be less than ∼3km ∼3km . From the observed rotating rate of impact spots, the rotational period of Jupiter is determined as 9h 9h 56m 56m 32s 32s at the southern latitude of 47∘∼49∘ 47∘∼49∘ .
4,600원
2.
1995.12
구독 인증기관 무료, 개인회원 유료
NONTHERMAL RADIO EMISSION FROM SNR IN THE PRE-SEDOV STAGE OF EVOLUTION : WEAK MAGNETIC APPROXIMATION
It has been recognized that the morphologies of the SNRs from the radio observation are "barrel shaped". To interpret the mechanism of the radiation and the physical state of the environments, we have analytically calculated the dynamical structure of the interacting region in the case where the ejectum has a steep power-law density profile(ρ∼r−n ρ∼r−n ) and the ambient medium has a shallow power-law density profile(ρ∼r−s ρ∼r−s ), assuming that the cosmic rays are isotropically accelerated in the shock wave and the magnetic fields are very weak. The calculated synchrotron radio maps show that the emission from the equator is intense and the emissions from the central and polar regions are less intense. Also the thicknesses of the shell are strongly dependent on s and weakly on n. The azimuthal intensity ratio α α increases as the efficiency of the cosmic ray acceleration increases and s decreases. We compared the results with the morphology of the SNR A. D. 1006(type I SNR). It does agree with the case of s = 0, w = 0.3 - 0.5. This value for w is consistent with the results by Eichler(1979). It provides us the evidence of the cosmic ray acceleration in the shock wave.
4,900원
3.
1995.12
구독 인증기관 무료, 개인회원 유료
We have developed a new device, Plate-to-CCD Convertor (PCC), to conveniently digitize photographic plates in a relatively short time without losing any plate information (Oh et al. 1995). Using this device we have performed surface photometry of 12 early type galaxies. We determined relative orientations and scales to analyze PCC images. We also determined an ellipticity, position angle of the major axis, and a4 a4 of each galaxy to quantify the distribution of surface brightness. We checked the performance and limitation of this device by comparing the PCC images with those digitized by the ST microdensitometer and those obtained with CCD observations.
6,300원
4.
1995.12
구독 인증기관 무료, 개인회원 유료
We analyze 271 data of the daily sunspot observations during the period of January 1 to December 31 in 1994 and present the daily relative sunspot numbers. During the 1994, the preliminary annual average of the relative sunspot numbers is found to be 32.9 based on 12.4 distinct spots in a single group for 2.2 spot groups. According to the appearance of 146 spot groups, our analysis shows that the mean life time of spot group is about 4 day and 19.2 hours.
4,000원
5.
1995.12
구독 인증기관 무료, 개인회원 유료
An introduction to the first CCD camera system in Bohyunsan Optica1 Astronomy Observatory(CCD#l) is presented. The CCD camera adopts modular dewar design of IfA(Institute for Astronomy at Hawaii University) and SDSU(San Diego State University) general purpose CCD controller. The user interface is based on IfA design of easy-to-use QUI program running on the NeXT workstation. The characteristics of the CCD#l including Gain, Charge Transfer Efficiency, rms Read-Out Noise, Linearity and Dynamic range is tested and discussed. The CCD#l shows 6.4 electrons RON and gain of 3.49 electrons per ADU, and the optimization resulted in about 27 seconds readout time guaranteeing charge transfer efficiency of 0.99999 for both direction. Linearity test shows that non-linear coefficient is 6×10−7 6×10−7 in the range of 0 to 30,000 ADU.
4,300원
6.
1995.12
구독 인증기관 무료, 개인회원 유료
The unique compact radio source, Sgr $A^*$, at the Galactic center show many observational signs that it is powered by supermassive black hole. Recent observations also imply that it is surrounded by winds from nearby IR sources. So we explore the model in which multiwavelength spectrum from Sgr $A^*$ is due to the spherical accretion of these winds onto the central supermassive black hole. Improving upon the previous work, we allowed the possibility that ions and electrons have different temperatures, included the Compton effects and pair processes. Electrons radiate via cyclosynchrotron and bresstrahlung with comptoniztion. We find that ion approaches the virial temperature ${\sim}10^{13}K$ while electron temperature saturates at ${\sim}10^{10}K$. However, decoupling between ion and electron does not greatly affect the shape of the emission spectrum. When the mass of the black hole is ${\sim}10^6M_{\odot}$, radio, IR, X-ray, $\gamma$-ray band spectrum is reasonably explained by the model. Yet Compton effect which is neglected in previous works produces significant emission in IR band, which is marginally compatible with observations. Pair production is negligible and annihilation lines cannot be observed.
4,300원
7.
1995.12
구독 인증기관 무료, 개인회원 유료
We have intensively examined the structure of photospheric magnetic fields obtained from the calculation of the polarized radiation transfer for the model atmosphere. To determine more reliable magnetic field in the photospheric region composed of umbra, penumbra and quite area, we have calculated the polarized radiative transfer for a magnetically sensitive spectral line, FeI 6302.5\AA 6302.5\AA , using our composite model representing three kinds of the atmospheric area distinguished by the pixel value of the Stokes I image over the region. Polarization data of the full Stokes parameters, used in this paper had been obtained from the vector magnetograph on Solar Flare Telescope of National Astronomical Observatory at Mitaka(MTK) in Japan. According to our investigation on the active region in the photosphere, it has been found that the large current density(≥8×102A/km2 ≥8×102A/km2 ) and shear angle(≥85∘ ≥85∘ ) should be distributed along the magnetic neutral line. To be compared with the results of MTK, our results in transverse magnetic field strength and direction are similar with those of MTK, however our longitudinal field strength at the center of the spot is somewhat(∼1000 ∼1000 Gauss) larger than MTK.
5,200원
8.
1995.12
구독 인증기관 무료, 개인회원 유료
According to historical records, Woon-Ju-Sa temple in Hwa-Soon, Chollanamdo, have had one thousand stone buddhas and one thousand stone pagodas, located south-west hill side of Woon-Ju-Sa is the Seven-Star-Stone(SSS). It consist of seven circular rocks with varying sizes that form a pattern similar to the constellation Ursa Major. SSS(Seven Star Stone) is an important astronomical remain because it might be one of the oldest records showing stellar brightness in Korea. We have compared the sizes of 888s with the magnitudes of stars of Ursa Major. It is found that the sizes of SSSs do roughly represent the magnitudes of Ursa Major stars in a way consistent with the magnitude scale used in Chun-Sang-Yul-Cha-Bun-Ya-Ji-Do(天象列次分野之圖) of Chosun.
5,100원
9.
1995.12
구독 인증기관 무료, 개인회원 유료
Recent discovery of an Io-related feature in Jupiter's auroral regions prompted us to search for an or multiplet at 1304Å in IUE aurora spectra. In three independent IUE spectra taken on January 18, 1981, we found an emission structure at 1304Å , with a signal-to-noise of about three. If the structure is due to the OI emission, then it is a direct evidence of oxygen ion precipitation, which may originate from Io and Io torus. The emission rates of the H2 H2 band systems and the or multiplet are about 50 kR and 150 R, respectively. We have constructed high resolution model spectra with the estimated emission rates of H2 H2 , OI and SI for the Goddard High Resolution Spectrograph (GHRS) onboard the Hubble Space Telescope. The model spectra clearly show the or and SI mulitplets separated from crowded H2 H2 Lyman and Werner band lines, and therefore it is promising to detect the OI and SI multiplets with the GHRS. Given the possibility that the lo-related feature may be caused by ion precipitations from the Io flux tube, it is likely that the OI emission may be detected in the footprint area of the IO flux tube.
4,000원
10.
1995.12
구독 인증기관 무료, 개인회원 유료
We have developed a graphic software for image processing of astronomical data obtained by observational equipment in Astronomical Observatory of Kyung Hee University. The essential hardware for running our computer program is simply composed of a PC with the graphic card to handle 256 colors and the color graphic monitor, including CCD camera system. Our software has been programmed in WINDOWS to provide good environments for users, by using various techniques of image processing on astronomical image data recorded in FITS format by KHCCD program(Jin and Kim, 1994) with a compressional mode. We are convinced that our results will be a fundamental and useful technique in the construction of data processing system and can be effectively used in any other observatories, as well as in data processing system of Kyung Hee University.
4,300원
