간행물
천문학회지 KCI 등재 SCOPUS Journal of The Korean Astronomical Society
- 발행기관 한국천문학회
- 자료유형 학술지
- 간기 반년간
- ISSN 1225-4614 (Print)2288-890X (Online)
- 수록기간 1968 ~ 2024
- 주제분류 자연과학 > 천문학 자연과학 분류의 다른 간행물
- 십진분류KDC 440DDC 520
권호리스트/논문검색
제26권 제1호 (1993년 6월) 7건
1.
1993.06
구독 인증기관 무료, 개인회원 유료
In order to explore the time dependence of the closure parameters of the two-fluid calculations for supernova remnants and the terminal shocks of stellar winds, we have considered a simple model in which the time evolution of the cosmic-ray distribution function was followed in the test-particle limit using the Bohm diffusion model. The particles are mostly accelerated to relativistic energy either in the free expansion phase of the SNRs or in the early phase of the stellar winds, so the evolution of the closure parameters during these early stages is substantial and should be followed correctly. We have also calculated the maximum momentum which is limited by either the age or the curvature of these spherical shocks. We found that SNRs expanding into the medium where the gas density decreases with the distance from the explosion center might be necessary to explain the observed power-law distribution of the galactic cosmic rays. The energy loss due to the escaping energetic particles has been estimated for the terminal shocks of the stellar winds.
4,300원
2.
1993.06
구독 인증기관 무료, 개인회원 유료
We have conducted BVI photographic surface photometry of four spiral galaxies NGC1087, NGC2715, NGC2844 and NGC3593, by making use of the Kiso Schmidt plates. Detailed examination of the morphological properties of the galaxies using isophotal maps and luminosity profiles showed that all the program galaxies have some peculiarities in their luminosity distributions. NGC1087 and NGC2715 have extremely small nuclei with inner rings which contain several bright HII regions. NGC2844 has a very large bulge whose luminosity dominates over the disk luminosity in all the radii. The I-band luminosity profile of NGC3593 shows shallower gradient than B- and V-band profiles. We were able to successfully decompose the luminosity profile into a bulge following de Vaucouleurs γ 1 / 4 − l a w and an exponential disk only for NGC 3953. Other galaxies have more complicated luminosit profiles.
5,500원
3.
1993.06
구독 인증기관 무료, 개인회원 유료
We have conducted surface photometry of a spiral galaxy NGC4419, by making use of photographic plates in U, B, V and R-bands taken by 105cm Schmidt Camera at Kiso Observatory. Two dimensional surface brightness distributions as well as luminosity profiles along the major axis are examined in detail to decipher the morphological properties of the galaxy. Analysis of the color distributions of NGC4419 shows that B-V and U-B colors remain constant throughout the galaxy with a weak trend of blue bulge in B-V color. The blue bulge might indicate an active star formation in the nucleus of NGC4419. For a quantitative analysis of the luminosity distribution of NGC4419, the observed luminosity profiles are decomposed into bulge and disk components, assuming the bulge component to follow de Vaucouleurs γ 1 / 4 − l a w while the disk component is assumed to be exponential. The fitting generally fails at the central part and at the shoulder near r = 15' where bulge and disk components overlap. The failure at the central part cannot be attributed wholly by the seeing disk since the core-radius of the central plateau is much larger than the width of point spread function. The failure at shoulder could be due to the luminosities from the spiral arms.
4,500원
4.
1993.06
구독 인증기관 무료, 개인회원 유료
The photometric evolution of cluster stars are examined for six synthetic clusters in the age range from 2.4 × 10 6 y r t o 7.6 × 10 8 y r by using the detailed evolutionary model calculation, and their results are compared with the observed integrated absolute magnitude and colors of 47 clusters. The reasonable agreements of the observed photometric parameters with the synthetic evolutionary sequences imply that there is a general form of time-dependent IMF including the noncoeval formation of stars and its detailed function is changed slightly with various environmental conditions of each primordial cloud.
5,200원
5.
1993.06
구독 인증기관 무료, 개인회원 유료
Using the Daeduk Radio Telescope, we have observed J = 1 → 0 transitions of 1 12 C O , 13 C O a n d C 18 O toward OMC-l. The column densities of 1 \~ 5 × 10 17 c m − 2 a n d 1 \~ 3 × 10 16 c m − 2 have been derived, for 13 C O and C 18 O , respectively, in the 11 ′ × 11 ′ region centered at Orion - KL. The double isotope ratio [ 13 C O ] / [ C 18 O ] was found to be larger than the cosmic abundance ratio by factors of 2 \~ 10 which may result from the chemical fractionation effect.
4,000원
6.
1993.06
구독 인증기관 무료, 개인회원 유료
We have mapped the C 3 H 2 2 12 − 1 01 transition line toward the Sgr A molecular cloud on a 1' grid spacing and derived C 3 H 2 column densities of 3 \~ 7 × 10 14 c m − 2 for molecular clouds of Sgr A. The fractional abundances of C 3 H 2 relative to H 2 are obtained to be 3 \~ 6 × 10 − 9 , which are slightly lower than that for the cold dark cloud TMC-1 but are enhanced by factors of 5-60 compared to those for Sgr B2 and the Orion extended ridge. We also estimate from the C 3 H 2 column densities total masses of \~ 10 6 M ⨀ for two clouds (M - 0.13 - 0.08 and M - 0.02 - 0.07), which are thought to be close to the virial equilibrium. We suggest that the large abundance of C 3 H 2 in Sgr A may be partly due to the activities of the Galactic center.
4,000원
7.
1993.06
구독 인증기관 무료, 개인회원 유료
We calculated the solar monopole abundance limit by comparing the observed solar neutrino flux and the calculation of non-fusion solar neutrino flux produced by Rubakov process in the solar core. We included the produced meson's enhancement effects by the surrounding ions in the solar core. We find that the monopole number N M < 1.9 × 10 20 ( 1 m b / σ 0 ) , where σ 0 is the characteristic proton decay cross section of Rubakov process. This is similar or stronger than strong limits obtained from neutron star's luminosity.
3,000원
