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1968년 ~ 2023년까지 1,187 건의 한국천문학회지를 격월간 확인하실 수 있습니다.
- The Korean Astronomical Society (The Korean Astronomical Society)
- 계간 (Quarterly)
- ISSN : 1225-4614 (ISSN : 1225-4614)
1225-4614
- DB구축현황 : 1,187건 (DB Construction : 1,187 Articles)
총 게시글 1,187건
페이지 89/119
881
- HESSER J. E.
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.111-118
- 1996
- 원문 바로보기
We review observational evidence bearing on the formation of a prototypical large spiral galaxy, the Milky Way. New ground- and space-based studies of globular star clusters and dwarf spheroidal galaxies provide a wealth of information to constrain theories of galaxy formation. It appears likely that the Milky Way formed by an combination of rapid, dissipative collapse and mergers, but the relative contributions of these two mechanisms remain controversial. New evidence, however, indicates that initial star and star cluster formation occurred simultaneously over a volume that presently extends to twice the distance of the Magellanic Clouds.
882
- LEE GEUNHO
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.103-104
- 1996
- 원문 바로보기
883
- MINN Y. K.
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.189-191
- 1996
- 원문 바로보기
We have made observations of the dark cloud, B5 in the transitions of <TEX>$H_2CO$</TEX>, J = <TEX>$1_{10} {\leftarrow} 1_{11}$</TEX>, and <TEX>$2_{12} {\to} 1_{11}$</TEX>. We compared the <TEX>$H_2CO$</TEX> result with the observational results of CO and with the visual extinction. There exists an overall correspondence of molecules and extinction. However, a detailed agreement is lacking. We discussed the kinematics and the spatial relationship of molecules and extinction in this cloud.
884
- CHOE G. S.
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.303-305
- 1996
- 원문 바로보기
The evolution of solar magnetic arcades is investigated with the use of MHD simulations imposing resistivity on sheared magnetic fields. It is found that there is a critical amount of shear, over which magnetic reconnection can take place ill an arcade-like field geometry to create a magnetic island. The process leading to reconnect ion cannot. be solely attributed to a tearing instability, but rather to a reactive evolution of the magnetic arcade under resistivity. The natures of the arcade reconnection are governed by the spatial pattern of resistivity. A fast reconnection with a small shock angle can only be achieved when the diffusion region is localized. In this case. a highly collimated reconnect ion outflow can tear the plasmoid into a pair, and most of principal features in solar eruptive processes are reproduced.
885
- KIM YONG HA
- Journal of the Korean astronomical society = 천문학회지
- 29, n.2
- pp.245-253
- 1996
- 원문 바로보기
We have analyzed infrared (IR) images of Jupiter which was observed at the McDonald Observatory, Texas, U.S.A., during the P/SHoemaker-LEvy 9 (SL9) impact period and about one week after the last impact. The IR images were obtained on the 2.7m telescope using a NICMOS array with filters to isolate the <TEX>$1.5{\mu}m\;NH_3\; band,\;the\;2.3{\mu}m\;CH_4\;band,\;the\;2.12{\mu}m\;H_2\;S(0)$</TEX> pressure-induced absorption, and the continua at <TEX>$1.58{\mu}m\;and\;2.0{\mu}m$</TEX> (short K-band). All images except those with the <TEX>$1.58{\mu}m$</TEX> continuum filter show bright impact sites against the relatively dark Jovian disk near the impact latitude of about <TEX>$45^{\circ}$</TEX> S. This implies that dusts originated from the impacts reflect the solar radiation at high altitudes before absorbed by stratospheric <TEX>$CH_4,\;NH_3 \;or\;H_2$</TEX>. The impact sites observed with the <TEX>$2.3{\mu}m$</TEX> filter are conspicuously bright against a very dark background. The morphology of impact sites, G, L, and H at 2.3 and <TEX>$2.12{\mu}m$</TEX> filters shows clearly an asymmetric structure toward the incident direction of the comet fragments, in agreement with the studies of visible impact images obtained with the Hubble Space Telescope. Comparisons of reflectances of G, L, and H sites with simple radiative transfer models suggest that optically thick dust layers were formed at high altitudes at which methane absorption attenuates incoming sunlight only by about <TEX>$1\%$</TEX>. The dust layers in these sites seem to form at about the same altitude regardless of the magnitude of the impacts, but they appear to descend gradually after the impacts. The dust layers have optical depths of 2-5, according to the models.
886
- CHOI MINHO
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.195-196
- 1996
- 원문 바로보기
We observed CO J = 2 <TEX>$\to$</TEX> 1 and J = 3 <TEX>$\to$</TEX> 2 lines toward several star formation regions with extremely high velocity (EHV) outflows: W3 IRS5, W28 A2, GL2591, S140, and Cepheus A. The full width of the wings are 90-235 km <TEX>$s^{-1}$</TEX>. Some wings show clear break of slope in the line profile implying that the nature of the EHV outflow is different from that of the high velocity outflow. We suggest that the EHV CO wing emission is tracing CO molecules in the stellar wind or jet which drives the high velocity outflow.
887
- KIM SUNGSOO S.
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.143-144
- 1996
- 원문 바로보기
Two-component models (normal star and degenerate star components) are the simplest realization of clusters with a mass spectrum because the high mass stars quickly evolve off leaving degenerate stars behind, while low mass stars survive for a long time as main-sequence stars. In the present study we examine the post-collapse evolution of globular clusters using two-component Fokker-Planck models that include three-body binary heating. We confirm that a simple parameter <TEX>${\epsilon}{\equiv} (E_{tot}/t_{rh})/(E_c/t_{rc})$</TEX> well describes the occurrence of gravothermal oscillations of two-component clusters. Also, we find that the degree of instability depends on the steepness of the mass function such that clusters with a steeper mass function are less exposed to instability.
888
- MOON YONG-JAE
- Journal of the Korean astronomical society = 천문학회지
- 29, n.2
- pp.207-215
- 1996
- 원문 바로보기
To derive coronal temperature, electron density and nonthermal velocity, we have analyzed high resolution spectra (e.g., Fe XII 338.3, Fe XII 352.1, Fe XIV 334.2, Fe XIV 353.8, Fe XV 284.2, Fe XV 321.8, Fe XV 327.0, Fe XVI 335.4, and Fe XVI 360.8) taken from AR 6615 by SERTS (Solar Extreme Ultraviolet Rocket Telescope and Spectrograph). Important findings emerging from the present study are as follows: (1) Temperature estimated from Fe XVI 335.4 and Fe XIV, 334.2 is <TEX>$\~2.4\times10^6 K$</TEX> and no systematic difference in temperature is found between the active region and its adjacent quiet region; (2) Mean electron density estimated from Fe XV is <TEX>$\~3\times10^9 cm^{-3}\;and\;\~10^{10} cm^{-3}$</TEX> from Fe XII and Fe XIV; (3) Mean density of the active region is found to be higher than that of the quiet region by a factor of 2; (4) Nonthermal velocity estimated from Fe XV and Fe XVI is <TEX>$20\times25 km\;s^{-l}$</TEX> which decreases with increasing ionization temperatures. This supports the notion that the nonthermal velocity declines outwards above the transition region.
889
- CHUN MOO-YOUNG
- Journal of the Korean astronomical society = 천문학회지
- 29, n.2
- pp.137-156
- 1996
- 원문 바로보기
NGC 6716 is an intermediate-age open cluster in Sagittarius. In this paper, we present the new UBV CCD photometry of the stars in the cluster, which is deeper than previous ones. From the color-color diagram and the color-magnitude diagram, we derived a reddening <TEX>$E_{B- V} = 0.17\pm0.03$</TEX> and a distance modulus of the cluster, <TEX>$(V - Mv)_o = 9.2\pm0.1$</TEX>. An age of the cluster is estimated as <TEX>$8\pm10^7 yrs$</TEX> from the latest isochrone. Luminosity function and mass function of the cluster are derived. The gradient of the mass function of bright stars is a bit steep, <TEX>$\Gamma = -1.85\pm0.05$</TEX>, and there is no distinct bump and dip in the mass function.
890
- LEE SANG-GAK
- Journal of the Korean astronomical society = 천문학회지
- 29, n.2
- pp.171-179
- 1996
- 원문 바로보기
We have obtained the J K images of the central region of the globular cluster M3 (NGC5272), using the <TEX>$256\pm256$</TEX> InSb array. We present JK photometry of bright red giant branch stars in the central <TEX>$2'.2\pm2'.2$</TEX> region of M3. The infrared color-magnitude diagrams are presented. The comparison of the red giant branch of M3 with that of M13 confirms that both globular clusters have similar metal abundances.