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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of The Korean Astronomical Society
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Journal DOI :
The Korean Astronomical Society
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Volume & Issues
Volume 34, Issue 4 - Dec 2001
Volume 34, Issue 3 - Dec 2001
Volume 34, Issue 2 - Jun 2001
Volume 34, Issue 1 - Apr 2001
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A FAST REDUCTION METHOD OF SURVEY DATA IN RADIO ASTRONOMY
LEE YOUNGUNG ;
Journal of The Korean Astronomical Society, volume 34, issue 1, 2001, Pages 1~8
We present a fast reduction method of survey data obtained using a single-dish radio telescope. Along with a brief review of classical method, a new method of identification and elimination of negative and positive bad channels are introduced using cloud identification code and several IRAF (Image Reduction and Analysis Facility) tasks relating statistics. Removing of several ripple patterns using Fourier Transform is also discussed. It is found that BACKGROUND task within IRAF is very efficient for fitting and subtraction of base-line with varying functions. Cloud identification method along with the possibility of its application for analysis of cloud structure is described, and future data reduction method is discussed.
OPTICAL MICROVARIABILITY OF BLAZARS
GHOSH K. K. ; KIM CHULHEE ; RAMSEY B. D. ; SOUNDARARAJAPERUMAL S. ;
Journal of The Korean Astronomical Society, volume 34, issue 1, 2001, Pages 9~15
We present the results of optical differential photometry of five blazars [PKS0219+428 (3C66A), PKS 0235+164 (AO 0235+16), H0414+019, PKS 0851+202 (OJ 287) and QSO 1807+698 (3C 371)] that were observed on 7 nights between November 05, 1997 and December 29, 1998, using the B and the V band filters. We have detected microvariations in four blazars (3C66A, AO 0235+16, H04l4+019, and OJ 287). In addition, the light curve of AO 0235+16 has displayed a mini-flare when the brightness of this source was decreasing. Night-to-night variations have also been detected in 3C66A, H04l4+019, and OJ 287. The results of our observations are discussed in the framework of accretion disk phenomena (magnetic flares or hot spots in accretion disks) and jet phenomena (plasma instabilities in jets).
STUDY OF M82 USING SPECTRA FROM THE INFRARED SPACE OBSERVATORY
SOHN JUNGJOO ; ANN H. B. ; PAK SOOJONG ; LEE H. M. ;
Journal of The Korean Astronomical Society, volume 34, issue 1, 2001, Pages 17~24
We have studied the central parts of M82, which is a well-known infrared luminous, starburst galaxy, by analyzing archival data from the Infrared Space Observatory (ISO). M82 was observed at 11 positions covering
45" from the center along the major axis. We analyzed 4 emission lines, [ArIII] 8.99
, [FeII] 25,98
, and [SiII] 34,815
data. The integrated flux distributions of these lines are quite different. The
line shows symmetric twin peaks at
18" from the center, which is a general characteristic of molecular lines in starburst or barred galaxies. This line appears to be associated with the rotating molecular ring at around
200 pc just outside the inner spiral arm. The relative depletion of the
line at the center may be due to the active star formation activity which dissociates the
molecules. The other lines have peaks at the center and the distributions are nearly symmetric. The line profiles are deconvolved assuming that both intrinsic and instrumental profiles are Gaussian. The velocity dispersion outside the core is found to be
. The central velocity dispersion is much higher than
, and different lines give different values. The large central velocity dispersion (
) is mostly due to the rotation, but there is also evidence for a high
for [ArIII] line. We also generated position-velocity maps for these four lines. We found very diverse features from these maps.
A NON-SPHERICAL MODEL FOR THE HOT OXYGEN CORONA OF MARS
KIM YONG HA ; SON SUJEONG ; YI YU ; KIM JHOON ;
Journal of The Korean Astronomical Society, volume 34, issue 1, 2001, Pages 25~29
We have constructed a non-spherical model for the hot oxygen corona of Mars by including the effects of planetary rotation and diurnal variation of the Martian ionosphere. Exospheric oxygen densities are calculated by integrating ensemble of ballistic and escaping oxygen atoms from the exobase over the entire planet. The hot oxygen atoms are produced by dissociative recombination of
, the major ion in the Martian ionosphere. The densities of hot oxygen atoms at the exobase are estimated from electron densities which have been measured to vary with solar zenith angle. Our model shows that the density difference of hot oxygen atoms between noon and terminator is about two orders of magnitude near the exobase, but reduces abruptly around altitudes of 2000 km due to lateral transport. The diurnal variation of hot oxygen densities remains significant up to the altitude of 10000 km. The diurnal variation of the hot oxygen corona should thus be considered when the upcoming Nozomi measurements are analyzed. The non-spherical model of the hot oxy-gen corona may contribute to building sophisticate solar wind interaction models and thus result in more accurate escaping rate of oxygens from Mars.
ON SMALL PERTURBATION DUE TO COLLISION OF PARTICLES IN AXISYMMETRIC ACCRETION DISK
YOO KYE WHA ;
Journal of The Korean Astronomical Society, volume 34, issue 1, 2001, Pages 31~33
The collision effects in particles of the accretion disk are examined by the use of small perturbation. The collision force is assumed to be equal to 2 vV. From the equations governing collisions of such particles the local dispersion relation is obtained.
A MODEL FOR MUV AIRGLOW FROM THE UPPER ATOMOSPHERE ABOVE THE KOREAN PENINSULA
MOON BONG-KON ; KIM YONG HA ; YI YU ; KIM JHOON ;
Journal of The Korean Astronomical Society, volume 34, issue 1, 2001, Pages 35~40
For the planned experiments of Korea Sounding Rocket-III (KSR-III), we have constructed a model of MUV dayglow in the mid-latitude. The model computes relative intensities of individual emission lines in the Vegard-Kaplan and 2PG band systems of
in the wavelength range of 2500-3500
. In addition to the emission lines, solar scattered continuum was computed by an extended LOWTRAN7 code, in which we have included solar scattering in altitudes higher than 100 km by using MSIS90 thermosphere model. Ratios among vibrational bands of VK and 2PG system, were computed from the observed MUV dayglow spectra of Cleary et al. (1995). The model provides MUV dayglow intensitiy profiles with a wavelength resolution of 3.13
as a function of altitude. The computed intensity profiles have been utilized in designing the KSR-III airglow photometers.
PERFORMANCE TEST OF THE BOAO MEDIUM DISPERSION SPECTROGRAPH (MDS)
KIM KANG-MIN ; KIM YEOJEONG ; YOON TAE SEOG ;
Journal of The Korean Astronomical Society, volume 34, issue 1, 2001, Pages 41~45
We tested the characteristics of the BOAO Medium Dispersion Spectrograph (MDS) such as the CCD capabilities, wavelength shift by gravity direction variation, slit illumination function and efficiency. Then we calculated the appropriate exposure time to obtain the given S/N ratio for several given magnitudes. Also the remaining problems to be improved were discussed.
ON THE ARMILLARY SPHERE OF NAM BYONG-CHUL-I
LEE YONG-SAM ; KIM SANG-HYUK ; NAM MOON-HYON ;
Journal of The Korean Astronomical Society, volume 34, issue 1, 2001, Pages 47~57
In this paper we have reconstructed an armillary sphere based on the Method of an Armillary Sphere Making described in the Volume 1 of The Collection of Writings on the Scientific Instruments-Uigijipsol (儀器輯說, two volumes) edited in the 1850's by Nam Byong-Chul (南秉哲, 1817-1863) who was a famous Korean states-man-scientist. Nam achieved convenience and accuracy in the measurements of stellar positions in the manner of selective setting the equatorial, ecliptic and horizontal poles by adding a pole axis exchange ring called Jaigeukkwon (載極圈) between the Three Arrangers of Time and Four Displacements. We made use of 3-dimensional graphic software for modelling Nam's armillary sphere which consisted of five layers-eight rings. Results of simulation showed that the pole axis exchange ring functioned properly in setting the equatorial, ecliptic and horizontal coordinates simply by exchange of positions of specified holes on the ring. We ascertained that the invention of Jaigeukkwon solved inherent problems in the conventional Chinese armillary sphere in computation of real ecliptic coordinates. It was revealed that Nam Byong-Chul made great contributions in the East Asian history of armillary sphere making.