간행물
천문학논총 KCI 등재 Publications of the Korean Astronomical Society
- 발행기관 한국천문학회
- 자료유형 학술지
- 간기 연3회
- ISSN 1225-1534 (Print)2287-6936 (Online)
- 수록기간 1984 ~ 2024
- 주제분류 자연과학 > 천문학 자연과학 분류의 다른 간행물
- 십진분류KDC 440DDC 520
권호리스트/논문검색
Volume 12 (1997년 12월) 15건
1.
1997.12
구독 인증기관 무료, 개인회원 유료
We have obtained theoretical calibration curves to convert the amount of polarization into the strength of magnetic field, by a numerical calculation of radiation transfer for the polarized spectral line of FeI 6303\AA. In our calculation, three kinds of atmospheric models (VAL-C, penumbra, umbra) have been used to make a proper calibration for an active region composed of quiet, penumbral and umbral areas. It was found that firstly, the results of our calculation depend highly on a kind of atmospheric model rather than on any other input parameters used in a model. Secondly, observed line profile showed m solar spectrum atlas proved to be very similar to the calculated profiles obtained by using a penumbra model. Finally, another method except this calibration curve should be developed to estimate correctly the distribution of magnetic field in solar active region from the observation of polarized spectral line.
5,700원
2.
1997.12
구독 인증기관 무료, 개인회원 유료
We have analyzed 223 data of the daily sunspot observations during the period of January 1 to December 31 in 1996 and present the daily relative sunspot numbers. During the 1996, the preliminary annual average of the relative sunspot numbers found to be 8.8 based on 3.7 distinct spots in a single group for 0.6 spot groups According to the appearance of 123 spot groups, our analysis shows that the mean life time of spot group is about 5 day and 5.8 hours. The proper conversion factor of the Korea Astronomy Observatory(KAO) derived from a comparison of one thousand one hundred and eighty observational sunspot numbers from 1992 to 1996 with those of international sunspot numbers is determined to be 1.17 instead of 0.97 which is in use.
4,200원
3.
1997.12
구독 인증기관 무료, 개인회원 유료
SOFT( So–––lar F––lare T––elescope So_larF_lareT_elescope ) installed at BOAO(Bohyunsan Optical Astronomy Observatory) is purposed for observing solar active regions using four refractors on single mount with a 400"×300" 400"×300" field of view: Two refractors with a diameter of 15cm(f15) are observe the white light and Hα Hα , and the other two refractors with a diameter of 20cm(f8) are observe the magnetic field distribution and Doppler shifts at the solar chromosphere. Three Lyot filters, one of the most important observational instruments, are installed on the optical rails for VMG, LMG, and Hα Hα that possible to very narrow pass band observation under high precision stability of temperature. From the combination of KD*P and quarter wave plate in the Lyot filter possible observe the magnetic fields strength and doppler shifts by using the characteristics of polarization components. In this paper, we introduce the basic characteristics, optical system, and monitor system of the SOFT.
4,200원
4.
1997.12
구독 인증기관 무료, 개인회원 유료
In this paper we present a newly improved telescope control software and a newly developed data analysis software package for effective use of the Solar Flare Telescope(SOFT) The telescope control software permits us to make not only auto tacking of the SOFT, but also quantitative measurement of the solar irradiation, allowing us to provide weather monitorings. In addition we introduce an IDL widget software package for both monochromatioc (MONO version) and polarimetric data (VMG version) analysis. The MONO version is capable of loading FITS files, changing colors and contrast, image processing, displaying plots, and saving displayed plots by selected formats The VMG version, on the other hand provides a calibration of polarimetric data and plots of reduced vector magnetic fields.
4,900원
5.
1997.12
구독 인증기관 무료, 개인회원 유료
We carried out high-resolution(FWHM=3' .3) HI 21 cm observations of the supernova remnant(SNR) PKS0607+17 and HII region S261 using Arecibo 305-m telescope. The observation was to investigate whether the high-velocity(HV) gas detected in the southern area of PKS0607+17 by Koo & Heiles(1991) is physically associated with the SNR or not. The velocity of the HV gas ranges from +64 km/s to +87 km/s, which is difficult to result from the Galactic rotation. The HV gas could be the gas accelerated by supernova blast wave. However, because the observation of Koo and Heiles(1991) was carried out using Hat Creek radio telescope(FWHM ≃ ≃ 36'), the association of the HV gas with the SNR could not be investigated. Using the Arecibo HI 21cm data, we have found that the HV gas appears m the southern part of the SNR and its velocity ranges from +61 km/s to +77 km/s. But the HV gas is scattered m the whole field, not only toward PKS0607+17 but also outside the SNR Accordingly the HV gas is probably not associated with the SNR, but is accidentally aligned along the same line of sight toward the SNR. Instead we have found that HI clouds at low velocities could be possibly associated with the SNR. In Arecibo HI 21cm channel maps the HI gas seems to surround the southern boundary of the SNR at VLSR VLSR = +19.6 ~ +40.2 km/s. But because the region of the Arecibo HI 21cm observation is not wide enough to examine the HI gas distribution, we investigated this area using the Berkely low-latitude HI survey data(Weaver & Williams 1974) too. There we found HI gas surrounding the radio continuum boundary of PKS0607+17 at VLSR VLSR = +21.6 ~ +258 km/s. It is possible that this HI gas is associated with the SNR, in which case, the velocity of the SNR Vo Vo ≃ ≃ +26 km/s, its distance d ≃ ≃ 12.5 kpc and its radius R ≃ ≃ 145 pc. If we assume that the expansion velocity is ~10 km/s, then the age of the SNR is ∼4.4×106 ∼4.4×106 years. PKS0607+17 could be one of the oldest SNRs in the Galaxy. We also studied HI propertities of the HII region S261, which is ∼1∘ ∼1∘ away from PKS0607+17. There has been no high-resolution m 21 cm observational study on S261. We discovered HI cloud located at the north-eastern part of S261 at VLSR VLSR = +5 km/s ~ +10 km/s, which is possibly associated with the HII region. The central velocity of the HI cloud VLSR VLSR = +7.2 km/s and the corresponding distance d = 1.5 kpc. This velocity is comparable to the radio recombination line velocities.
5,800원
6.
1997.12
구독 인증기관 무료, 개인회원 유료
The A-X (0-0) band of CS, which appears in high dispersion IUE spectra of comets Halley (1982i) and Wilson (19861), has been investigated in detail. We developed models, which include fluorescence and collisional processes We found that in order to account for the observed emission band precisely, IUE tracking errors should be included in line shape calculations it has been found that rotational excitation by electrons is a dominant process in determining populations of rotational ground states. We derived an electron density of 2.0×104/cm3 2.0×104/cm3 at several thousand kilometers from the comet Wilson's nucleus by examining collisional influence on the CS band structure. We presented a band model for the 0-0 band of C34S C34S and discussed the detectability of 34S 34S spectroscopically.
4,600원
7.
1997.12
구독 인증기관 무료, 개인회원 유료
We obtained the CN(ΔV=0 ΔV=0 ) and C2(ΔV=0,±1 C2(ΔV=0,±1 ) spectra of comet Hale-Bopp(C/1995 O1) at the Kyunghee Observatory and Bohyunsan Astronomical Observatory between March 7 and May 12, 1997 The fluxes for each molecular band were measured and then the production rates and column densities of CN and C2 C2 were calculated using a simple model. The resultantproduction rates of CN and C2 C2 are logQ(CN)=27.4 at r=0.94 AU(preperihelion) and logQ(C2)=27.3 logQ(C2)=27.3 at r=0.94 AU(postperihelion), respectively.
4,200원
8.
1997.12
구독 인증기관 무료, 개인회원 유료
We have developed a spherical FCT code in order to simulate the interaction of supernova remnants with stellar wind bubbles. We assume that the density profile of the supernova ejecta follows the Chevalier mode1(1982) where the outer portion has a power-law density distribution(ρ∝γ−n ρ∝γ−n ) and the SN ejecta has a kinetic energy of 1051 1051 ergs. The structure of wind bubble has been calculated with the stellar mass loss rate ˙ M=5×10−6M⊙/yr M˙=5×10−6M⊙/yr and the wind velocity υ=2×103 υ=2×103 km/s We have simulated seven models with different initial conditions In the first two models we computed the evolution of SNRs with n=7 and n=14 in the uniform medium The numerical results agree with the Chevalier's similarity solution at early times. When all of the power-law portion of the ejecta is swept up by the reverse shock, the evolution slowly converges to the Sedov-Taylor stage. There is not much difference between the two cases with different n's The other five models simulate SNRs produced inside wind bubbles. In model III, we consider the SN ejecta of 1.4 M⊙ M⊙ and the radius of bubble ~2.76 pc so that ratio of the mass α(=MW.S/Mej α(=MW.S/Mej is 2. We follow the complex hydrodynamic flows produced by the interaction of SN shocks with stellar shocks and with the contact discontinuities, In the model III, the time scale for the SN shock to cross the wind shell τcross τcross is similar to the time scale for the reverse shock to sweep the power-law density profile τbend τbend . Hence the SN shock crosses the wind shell. At late times SN shock produces another shell in the ambient medium so that we have a SNR with double shell structure. From the numerical results of the remaining models, we have found that when τcross/τbend≤2 τcross/τbend≤2 , or equivalently when α≤50 α≤50 , the SNRs produced inside wind bubbles have double shell structure. Otherwise, either the SN shock does not cross the wind shell or even if it crosses at one time, the reverse shock reflected at the center accelerates the wind shell to merge into the SN shock Our results confirm the conclusion of Tenorio-Tagle et a1(1990).
8,000원
9.
1997.12
구독 인증기관 무료, 개인회원 유료
In this letter we will investigate the possibility whether primordial black holes can grow to become galactic black holes or not. We find that even a primordial black hole with the probable maximum mass cannot grow in a short timescale. Only a hole with the initial mass of order ∼104M⊙ ∼104M⊙ can significantly grow to become a galactic hole.
3,000원
10.
1997.12
구독 인증기관 무료, 개인회원 유료
The collision model of the disk, based on collisions between the particles in the disk, is summarized. The dependence of disk stability on the collision of the particles is demonstrated. The energy spectrum produced in the disk is numerically calculated. We concluded that the results are not largely different from those of the standard disk model. It implies that the collision of the particles inside the disk may be considered here.
4,000원
11.
1997.12
구독 인증기관 무료, 개인회원 유료
In order to reduce the small scale fluctuation resulting from shearing holograpy(Park et. al. 1997), differential panel adjustments were performed for 14 m radio telescope of Taeduk Radio Astronomy Observatory with T2 theodolite It appears that this method improves the surface accuracy by about 50μm 50μm . The measured surface accuracy is, at best, 170μm 170μm . The beam efficiency at 86.2 GHz is estimated to be 44% We also found that the elevation at which Park et. al. performed holography was too low.
4,000원
12.
1997.12
구독 인증기관 무료, 개인회원 유료
Detailed low spectral resolution observations of the spectrum have been made for three early spectral type standard stars, HR718, HR1544, HR3454, respectively, for the wavelength region 4,300 A to 7,500 A, using the Bohyunsan Optical Astronomy Observatory (BOAO) Middle- Dispersion Spectrograph. These standard stars were chosen from well-known bright northern standard stars. All of the observed long slit spectral data has been reduced and analyzed using the IRAF reduction procedure. The derived extinction coefficients are compared with the other observatory result. The derived value can be used in the determination of flux calibration of BOAO spectroscopic observation. However, until the high quality data are secured from a new series of observation in the blue region and are re-analyzed together, the extinction coefficients below the 4,000 A wavelength remains unknown.
4,000원
13.
1997.12
구독 인증기관 무료, 개인회원 유료
We have numerically simulated the evolution of supernova remnant VRO 42.05.01(G166.0+43) in order to understand its morphology m radio and X-ray observations as well as the dynamical interaction of the supernova remnant with the surrounding interstellar medium. The Radio and ROSAT observations suggest that the unusual morphology of VRO 42.05.01 is caused by a supernova blast wave breaking out of the cloud boundary where the supernova event occurred, and expanding into another cloud across a much less dense and presumably hot cavity. Our numerical results are consistent with the interactions of a passing supernova blast wave with the clouds across the cavity. We discuss the implications of our results on the dynamics of VRO 42.05.01 such as the reverse shocks, the rejuvenation of the hot cavity, and the reflected shocks formed by the reverse shock collisions. We have theoretically mapped the radio continuum(1.4 GHz) and X-ray(0.1~2 keV) morphology which are consistent with the observational ones.
4,200원
14.
1997.12
구독 인증기관 무료, 개인회원 유료
We present a code which identifies individual clouds in crowded region using IMFORT interface within Image Reduction and Analysis Facility (IRAF). We define a cloud as an object composed of all pixels in longitude, latitude, and velocity that are simply connected and that lie above some threshold temperature. The code searches the whole pixels of the data cube in efficient way to isolate individual clouds. Along with identification of clouds it is designed to estimate their mean values of longitudes, latitudes, and velocities. In addition, a function of generating individual images (or cube data) of identified clouds is added up. We also present identified individual clouds using a 12CO survey data cube of Galactic Anticenter Region (Lee et al. 1997) as a test example. We used a threshold temperature of 5σ 5σ rms noise level of the data With a higher threshold temperature, we isolated subclouds of a huge cloud identified originally. As the most important parameter to identify clouds is the threshold value, its effect to the size and velocity dispersion is discussed rigorously.
4,300원
15.
1997.12
구독 인증기관 무료, 개인회원 유료
The general photometric, spectroscopic, and kinematic properties of the late type halo stars are investigated from a sample of known true halo stars. Halo stars are distributed in a lower left region of infrared (J-H) vs (H-K) color-color diagram, which is recomfirmed to be useful for selection of halo stars. They move with average velocity components of 9 km/sec, -14 km/sec, and 5 km/sec in U, V, and W directions respectively. They are distributed seperately from disk stars in a diagram of metallicity index, CaH1/TiO5 vs (R-I).
4,900원
