Go to the main menu
Skip to content
Go to bottom
REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Journal of Astronomy and Space Sciences
Journal Basic Information
Journal DOI :
The Korean Space Science Society
Editor in Chief :
Volume & Issues
Volume 18, Issue 3 - Dec 2001
Volume 18, Issue 2 - Nov 2001
Volume 18, Issue 1 - Jun 2001
Selecting the target year
CAN A WIND MODEL MIMIC A CONVECTION-DOMINATED ACCRETION FLOW MODEL\ulcorner
Chang, Heon-Young ;
Journal of Astronomy and Space Sciences, volume 18, issue 1, 2001, Pages 1~6
In this paper we investigate the properties of advection-dominated accretion flows (ADAFs) in case that outflows carry away infalling matter with its angular momentum and energy. Positive Bernoulli number in ADAFs allow a fraction of the gas to be expelled in a form of outflows. The ADAFs are also unstable to convection. We present self-similar solutions for advection-dominated accretion flows in the presence of outflows from the accretion flows(ADIOS). The axisymmetric flow is treated in variables integrated over polar sections and the effects of outflows on the accretion flow are parameterized for possible configurations compatible with the one dimensional self-similar ADAF solution. We explicitly derive self-similar solutions of ADAFs in the presence of outflows and show that the strong outflows in the accretion flows result in a flatter density profile, which is similar to that of the convection-dominated accretion flows(CDAFs) in which convection transports the angular momentum inward and the energy outward. There two different versions of the ADAF model should show similar behaviors in X-ray spectrum to some extent. Even though the two models may show similar behaviors, they should be distinguishable due to different physical properties. We suggest that for a central object of which mass is known these two different accretion flow should have different X-ray flux value due to deficient matter in the wind model.
METALLICITY OF GLOBULAR CLUSTER NGC 5053 FROM VI CCD PHOTOMETRY
Sohn, Young-Jong ;
Journal of Astronomy and Space Sciences, volume 18, issue 1, 2001, Pages 7~14
Red giant branch shape and the luminosity of horizontal branch on the (V-I)-V CMD are used to derive the metallicity the globular cluster NGC 5053. The metallicities of NGC 5053 derived by SMR method ([Fe/H]=-2.62
0.07) and the relation between[Fe/H] and
([Fe/H]=-2.50) are in good agreement with previously determined values. This result confirms that the morphologies of RGB and HB on the (V-I)-V CMDs can be good indirect photometric metallicity indicators of galactic globular clusters.
THE EVOLUTION OF AGB STARS ON INFRARED 2-COLOR DIAGRAMS
Suh, Kyung-Won ; Lee, Jae-Woo ; Kim, Hak-Youn ;
Journal of Astronomy and Space Sciences, volume 18, issue 1, 2001, Pages 15~20
We present infrared 2-color diagrams of AGB stars from the observations at near infrared and IRAS point source catalog (PSC) data. We compile the observations for thousands of newly identified OH/IR stars and carbon stars. We compare the observations with the theoretical evolutionary tracks of AGB stars. From the new observational data base and theoretical tracks, we discuss the meaning of the infrared 2-color diagrams.
STUDIES OF GRAVITY WAVES USING MICHELSON INTERFEROMETER MEASUREMENTS OF OH(3-1)BANDS
Won, Young-In ; Cho, Young-Min ; Lee, Bang-Yong ; Kim, J. ;
Journal of Astronomy and Space Sciences, volume 18, issue 1, 2001, Pages 21~26
As part of a long-term program for polar upper atmospheric studies, temperatures and intensities of the OH(3-1) bands were derived from spectrometric observations of airglow emissions over King Sejong station(
). These measurements were made with a Michelson interferometer to cover wavelength regions between 1000nm and 2000 nm. A spectral analysis was performed to individual nights of data to acquire information on the waves in the upper mesosphere/lower thermosphere. It is assumed that the measured fluctuations in the intensity and temperature of the OH (3-1) airglow were caused by gravity waves propagating through the emission layer. Correlation of intensity and temperature variation revealed oscillations with periods ranging from 2 to 9 hours. We also calculated Krassovsky’s parameter and compared with published values.
A STATISTICAL STUDY OF MAGNETIC STORM RECOVERY PHASE: PRELIMINARY RESULTS
Lee, D.Y. ; Hwang, J.A. ; Min, K.W. ; Lee, E.S. ; Cho, K.S. ; Kim, S.G. ; Bae, S.H. ;
Journal of Astronomy and Space Sciences, volume 18, issue 1, 2001, Pages 27~32
A statistical study has been performed of the magnetic storm recovery phase using the Dst index for 102 storm events in the interval January 1996 to December 1998. In 43 cases (or 42%) out of our 102 events, the recovery phase exhibits fast recovery (kaking about 8 hours or less) at its initial stage or for the entire recovery period. Since this fast recovery can be explained by the fast charge exchange less of
ions which mostly com from the ionosphere, and since a fraction of
ions is of ionospheric origin as well, our statistical result supports the view that the source of ring current ions in many magnetic storms can be terrestrial.
He II RAMAN SCATTERED LINE BY NEUTRAL HYDROGEN IN THE BIPOLAR PLANETARY NEBULA M2-9
Journal of Astronomy and Space Sciences, volume 18, issue 1, 2001, Pages 33~42
In the spectrum of the young bipolar planetary nebula M2-9 obtained from the 1.5m telescope at the Cerro Tololo Inter-American Observatory, we detected the He II feature at 6545
that are proposed to be formed via Raman scattering by atomic hydrogen. However, in the same spectrum, the He II emission lines at 6527
are absent, which implies that the He II emission region is hidden from our line of sight and that the H I scattering region is pretty much extended not to be obscured entirely. We performed photoionization computations to estimate the physical size of the He II emission line region to be
, from which the location and dimension of the obscuring circumstellar region are inferred and the temperature of the central star must exceed
. The angular size of the circumstellar region responsible for the obscuration of the He II emission region is ~1" with the assumption of the distance 01 kpc to M2-9, which is consistent with the recent image of M2-9 obtained with the Hubble Space Telescope.
PHOTOELECTRIC OBSERVATIONS AND ANALYSIS OF THE CONTACT BINARY W UMA
Journal of Astronomy and Space Sciences, volume 18, issue 1, 2001, Pages 43~54
The unpublished photoelectric observations of the contact binary W UMa in ultraviolet, blue, and yellow bandpasses made on four nights during the obsrving seasons from April, 1984 to May, 1985 were presented. From our observations new eleven times of minimum light were determined. By using the 1993 WD binary model our light curves were analyzed and new photometric solutions of W UMa were obtained.
CCD PHOTOMETRY OF W UMa TYPE BINARY TY UMa
Journal of Astronomy and Space Sciences, volume 18, issue 1, 2001, Pages 55~62
We present VRI CCD photometry of W UMa type binary TY UMa. The light curves show that the secondary minimum is deeper than the primary minimum and the maximum I (
brighter than the maximum II (
). The V light curve has been analyzed and the photometric solutions have been determined by the method of Wilson & Devinney differential correction. We adopted the spot model to explain the asymetric light curve.
THE IMPROVEMENT OF POSITION ACCURACY USING INVERTED DGPS
Journal of Astronomy and Space Sciences, volume 18, issue 1, 2001, Pages 63~70
IDGPS(Inverted Differential Global Positioning System) is one of technique improving the accuracy of GPS positioning and is mostly used for tracking an automatic vehicle. In the IDGPS, the user send it’s GPS position and related satellite information to dispatcher, and the corrections are made at the dispatcher to get corrected user position. IDGPS suffered correction degradation as the baseline become large. This problem is resolved using NIDGPS(Network IDGPS). As the experimental results are demonstrated, the improvement of position accuracy using IDGPS and NIDGPS is verified.
SIMULATION OF SHIELDING EFFECTS ON THE TOTAL DOSE OBSERVED IN TDE OF KITSAT-1
Journal of Astronomy and Space Sciences, volume 18, issue 1, 2001, Pages 71~80
The threshold voltage shift observed in TDE (Total Dose Experiment) on board the KITAT-1 is converted into dose (rad(
)) using the result of laboratory calibration with Co-60 gamma ray source in KAERI (Korea Atomic Energy Research Institute). Simulation using the NASA radiation model of geomagnetosphere verifies that the dose difference between RADFET1 and RADFET3 observed on KITSAT-1 comes from the difference in shielding thickness at the position of these RADFETs.
THERMAL AND STRUCTURAL ANALYSIS OF FIMS GRATING
Journal of Astronomy and Space Sciences, volume 18, issue 1, 2001, Pages 81~93
Far ultraviolet IMaging Spectrograph (FIMS) should be designed to maintain its structural stability and to minimize optical performance degradation in launch and in operation enviroments. The structural and thermal analyzes of grating and grating mount system, which are directly related to FIMS optical performance, was performed using finite element method. The grating mount was made to keep the grating stress down, while keeping the natural frequency of the grating mount higher than 100 Hz. Transient and static thermal analyzes were also performed and the results shows that the thermal stress on the grating can be attenuated sufficiently. The optical performance variation due to temperature variation was with the allowed range.