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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Astronomy and Space Sciences
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The Korean Space Science Society
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Volume 13, Issue 2 - Jun 1996
Volume 13, Issue 1 - Jun 1996
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CCD PHOTOMETRY OF FIELD RR LYRAE STARS I. PERIOD CHANGES OF SV ERI AND XX AND
Joo, Jong-Myung ; Rey, Soo-Chang ; Lee, Young-Wook ;
Journal of Astronomy and Space Sciences, volume 13, issue 1, 1996, Pages 1~8
CCD time series photometry was performed for two Oosterhoff type II field RR Lyrae stars, SV Eri and XX And, to construct light curves in B and V bands. The maximum light times from our observations were combined with those in the literature to construct phase shift diagrams, from which we determined the period change rates
. We obtained large positive period change rates for these stars, which are expected from current evolutionary models if these stars are evolving rapidly from blue to red toward the end of core helium burning phase.
SEARCH OF SHORT-PERIOD PULSATING VARIABLES(I)
Kim, Chul-Hee ; Park, Nam-Kyu ;
Journal of Astronomy and Space Sciences, volume 13, issue 1, 1996, Pages 9~18
CCD differential photometry was carried out for seven stars in the "New Catalogue of Suspected Variable Stars" in order to discover new short-period pulsating variables such as low and high amplitude
Scuti stars and RR Lyrate stars. It was found that NSV1132, NSV3031, and NSV5119 are RRs, Irregular, and low amplitude
Scuti type variables respectively.
HOMOGENEOUS SOLUTION FOR SW LACERTAE
Kim, Kyung-Joo ; Kang, Young-Woon ;
Journal of Astronomy and Space Sciences, volume 13, issue 1, 1996, Pages 19~31
We have analyzed collected photoelectric light curves for light variations of SW Lac. The method of Fourier analysis was adopted to quantify the light variation from season to season. We found the linear relation between the Fourier coefficient, B1 and the magnitude difference between two maxima. The total light of the system has been decreased as much as 0m.04 during approxiamately 20 years time interval. Photoelectric parameters including spot parameters for all light curves were obtained by the method of the Wilson and Devinney differential correction in order to secure the variations of parameters from season to season. SW Lac, not like RS CVn type stars, required to adjust all parameters as well as spot parameters for a reasonable fit to the observations of each epoch. A surface temperature of cooler star is one of the most sensitive parameters to affect a shape of light curve of SW Lac. We conclude that the shape of light curve of SW Lac varies even during one season as well as season to season. The light curve is mainly caused by inhomogeneous surface temperature due to strong chromospheric activity of the system.
PHOSPHINE AND JUPITER'S GREAT RED SPOT
Kim, Sang-Joon ;
Journal of Astronomy and Space Sciences, volume 13, issue 1, 1996, Pages 32~39
Voyager IRIS (Infrared Interferometer Spectrometer) observations of Jupiter's Great Red Spot (GRS) have been examined in order to extract the vertical distribution of phosphine. To the accuracy than can be achieved from this approach, there appears to be no difference between the PH3 distribution over the GRS compared with the distribution over the neighboring South Tropical Zone. This result is at variance with a pre-Voyager prediction of an enhancement of PH3 over the GRS resulting in the preferential production of red phosphorous in this location on the planet (Prinn & Lewis 1975). The composition of the red material remains an open question.
ALGORITHM OF SEU RATE PREDICTION INSIDE SPACECRAFTS
Kim, Y.C. ; Lee, J.H. ; Shin, Y.H. ; Min, K.W. ;
Journal of Astronomy and Space Sciences, volume 13, issue 1, 1996, Pages 40~47
One of the important effects of the space environment on the satellites and spacecrafts is the single event upsets (SEUs) which are caused by the high energy particles in space. A SEU occurs when an ionizing radiation produces a burst of electron-hole pairs in a digital microelectronic circuit and causes the charge state to change. We have developed and integrated a software package which can estimate the SEU rates for any specified locations or altitudes under various geophysical conditions. We report in this paper the algorithm of the software and the results for some devices with known parameters. We also compare the results with actual observations made by Akebono.
LINEAR PROGRAMMING SOLUTIONS OF GENERALIZED LINEAR IMPULSIVE CORRECTION FOR GEOSTATIONARY STATIONKEEPING
Park, Jae-Woo ;
Journal of Astronomy and Space Sciences, volume 13, issue 1, 1996, Pages 48~54
The generalized linear impulsive correction problem is applied to make a linear programming problem for optimizing trajectory of an orbiting spacecraft. Numerical application for the stationkeeping maneuver problem of geostationary satellite shows that this problem can efficiently find the optimal solution of the stationkeeping parameters, such as velocity changes, and the points of impulse by using the revised simplex method.
CCD PHOTOMETRY OF THE GLOBULAR CLUSTER M30
Journal of Astronomy and Space Sciences, volume 13, issue 1, 1996, Pages 55~62
We present UBV CCD photomety of the metal-poor globular cluster M30. The data were obtained using the 40 inch telescope at Mt. Stromlo and Siding Spring Observatory (MSSSO). We used DAOPHOT CCD reduction package in order to obtain Color-Magnitude Diagram (CMD). We have derived some fundametal parameters of the globular cluster such as metal abundance ([Fe/H]), helium abundance (Y), and distance modulus (m-M) from the CMD. The derived parameters were [Fe/H]=-2.50, Y=0.28, and (m-M)=14.64. From the latter, the distance of 8.3kpc is obtained. Despite the photometric uncertainty near the main-sequence turnoff, we estimate the age of M30 to be 1.6
3 Gyrs from the Revised Yale Isocyrones. If [O/Fe]=+0.4, this age will be reduced to 14.2
PHOTOELECTRIC OBSERVATIONS OF CLOSE BINARY AG PERSEI AND ITS APSIDAL MOTION ANALYSIS
Journal of Astronomy and Space Sciences, volume 13, issue 1, 1996, Pages 63~71
A total of 546 UBV photoelectric observations of AG Per was carried out from January to December in 1993 at Chungbuk National University Observatory. With our observations, UBV light curves were constructed, three minimum times of JDHel. 2449284.213, JDHel. 2449360.060, and JDHel. 2449363.192 were determined. The phase displacement of secondary minimum time
=-0.046 were determined and orbital eccentricity e=0.071 was calculated. Forty-five times of minimum light (including ours) were collected from the literature and plotted on O-C diagram. We analyzed these data and apsidal motion period of U=76.17 (years) was obtained. Using e and U for AG Per, the internal structure constant, log k2, was found to be -2.13.
OBITAL ELEMENT ANALYSIS OF A SHORT PERIOD ECLIPSING BINARY UV PISCIUM
Journal of Astronomy and Space Sciences, volume 13, issue 1, 1996, Pages 72~78
We evaluated the orbital elements of BV light curves of a short period RS CVn type eclipsing binary system UV Picsium that shows complication light variation, by analyzing with the Winson-Devinney's differential correction method. Because the analyzed light curves shows large light variation at outside eclipse region, we assumed spotted region of the primary component and calculated its position and size. The results show the UV Psc is a detached binary system of nearly the same radii and the primary component has high mass with high temperature. However this result is not consistant with customary stellar models, thus requires more observational data to confirm this problem.
EFFECTS OF WIND VELOCITY DRIVEN BY ALFVEN WAVES ON THE LINE PROFILES FOR 32 CYG
Journal of Astronomy and Space Sciences, volume 13, issue 1, 1996, Pages 79~89
We calculate the theoretical line profiles for 32 Cyg in order to investigate the influence of various velocity fields. Line profiles are calculated with wind accelerations driven by Alfven waves and described by velocity parameters. The results for Alfvenic wave model show weakened line profiles. For the orbital phases
=0.06 the Alfvenic models show strong absorption part due to very low densities at the surface of the supergiant. Hence, we conclude the velocity gradient of the wind near the supergiant could influence on the theoretical line formation.