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1968년 ~ 2024년까지 1,211 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 : 1,211건 (DB Construction : 1,211 Articles)
총 게시글 1,211건
페이지 65/122
641
- LEE HEE-WON
- Journal of the Korean astronomical society = 천문학회지
- 36, n.2
- pp.55-60
- 2003
- 원문 바로보기
In Lee, Kang & Byun (2001) the discovery of Raman scattered 6545 A feature was reported in symbiotic stars and the planetary nebula M2-9. The broad emission feature around 6545 A is formed as a result of Raman scattering of He II n = 6 <TEX>$\to$</TEX> n = 2 photons by atomic hydrogen. In this paper, we introduce a method to compute the equivalent width of He II <TEX>$\lambda$</TEX> 1025 line and present an optical spectrum of the symbiotic star RR Telescopii as an example for a detailed illustration. In this spectrum, we pay attention to the broad H<TEX>$\alpha$</TEX> wings and the Raman scattered He II 6545 feature. The broad Ha wings are also proposed to be formed through Raman scattering of continuum around Ly<TEX>$\beta$</TEX> by Lee (2000), and therefore we propose that the equivalent width of the He II <TEX>$\lambda$</TEX> 1025 emission line is obtained by a simple comparison of the strengths of the 6545 feature and the broad H<TEX>$\alpha$</TEX> wings. We prepare a template H<TEX>$\alpha$</TEX> wing profile from continuum radiation around Ly<TEX>$\beta$</TEX> with the neutral scattering region that is supposed to be responsible for the formation of Raman scattered He II 6545 feature. Isolation of the 6545 feature that is blended with [N II] <TEX>$\lambda$</TEX> 6548 is made by using the fact that [N II] <TEX>$\lambda$</TEX> 6584 is always 3 times stronger than [N II] <TEX>$\lambda$</TEX> 6548. We also fit the 6545 feature by a Gaussian which has a width 6.4 times that of the He II <TEX>$\lambda$</TEX> 6527 line. A direct comparison of these two features for RR Tel yields the equivalent width <TEX>$EW_{Hel025} = 2.3{\AA}$</TEX> of He II <TEX>$\lambda$</TEX> 1025 line. Even though this far UV emission line is not directly observable due to heavy interstellar extinction, nearby He II lines such as He II <TEX>$\lambda$</TEX> 1085 line may be observed using far UV space instruments, which will verify this calculation and hence the origins of various features occurring in spectra around H<TEX>$\alpha$</TEX>.
642
- KANG SANGJUN
- Journal of the Korean astronomical society = 천문학회지
- 36, n.3
- pp.75-80
- 2003
- 원문 바로보기
When a bright astronomical object (source) is gravitationally lensed by a foreground mass (lens), its image appears to be located at different positions. The lens equation describes the relations between the locations of the lens, source, and images. The lens equation used for the description of the lensing behavior caused by a lens system composed of multiple masses has a form with a linear combination of the individual single lens equations. In this paper, we examine the validity of the linear nature of the multi-lens equation based on the general relativistic point of view.
643
- MIN KYOUNG W.
- Journal of the Korean astronomical society = 천문학회지
- 36, n.suppl1
- pp.109-115
- 2003
- 원문 바로보기
We report the results of the ionospheric measurement obtained from the instruments on board the Korea Multi-Purpose Satellite - 1 (KOMPSAT-l). We observed a deep electron density trough in the nighttime equatorial ionosphere during the great magnetic storm on 15 July 2000. We attribute the phenomena to the up-lifted F-layer caused by the enhanced eastward electric field, while the spacecraft passed underneath the layer. We also present the results of our statistical study on the equatorial plasma bubble formation. We confirm the previous results regarding its seasonal and longitudinal dependence. In addition, we obtain new statistical results of the bubble temperature variations. The whole data set of measurement for more than a year is compared with the International Reference Ionosphere (IRI). It is seen that the features of the electron density and temperature along the magnetic equator are more prominent in the KOMPSAT-l observations than in the IRI model.
644
- KIM SANG CHUL
- Journal of the Korean astronomical society = 천문학회지
- 36, n.1
- pp.13-19
- 2003
- 원문 바로보기
We present a study of the old open cluster Trumpler 5 (Tr 5), based on the CDS archival data. From the color-magnitude diagrams of Tr 5, we have found the positions of main-sequence turn-off (MSTO) and red giant clump (RGC) stars. Using the mean magnitude of the RGC stars, we have estimated the reddening toward Tr 5, E(B - V) = 0.60 <TEX>$\pm$</TEX> 0.10. Using the stars common in two data sets and the theoretical isochrones of Padova group, we have estimated the distance modulus <TEX>$V_o - M_v = 12.64 {\pm} 0.20 (d = 3.4 {\pm} 0.3 kpc)$</TEX>, the metallicity [Fe/H) = -0.30 <TEX>$\pm$</TEX> 0.10, and the age of 2.4 <TEX>$\pm$</TEX> 0.2 Gyr (log t = 9.38). These metallicity and distance values are consistent with the relation between the metallicity and the Galactocentric distance of other old open clusters, for which we obtain the slope of <TEX>${\Delta}[Fe/H]/ R_{gc} = -0.064 {\pm} 0.010\;dex\;kpc^{-1}$</TEX>.
645
- AHN SANG-HYEON
- Journal of the Korean astronomical society = 천문학회지
- 36, n.3
- pp.145-148
- 2003
- 원문 바로보기
P-Cygni type Ly<TEX>$\alpha$</TEX> from starburst galaxies, either nearby galaxies or Lyman Break galaxies, are believed to be formed by galactic outflows such as galactic supershells or galactic superwinds. We develope a Monte Carlo code to calculate the Ly<TEX>$\alpha$</TEX> line transfer in a galactic supershell which is expanding and formed of uniform and dusty neutral hydrogen gas. The escape of Ly<TEX>$\alpha$</TEX> photons from the system is achieved by a number of back-scatterings. A series of emission peaks are formed by back-scatterings. When we observe P-Cygni type Ly<TEX>$\alpha$</TEX> emissions of starforming galaxies, we can usually see merely singly-peaked emission. Hence the secondary and the tertiary emission humps should be destroyed. In order to do this, dust should be spatially more extended into the inner cavity than neutral supershell. We find that the kinematic information of the expanding supershell is conserved even in dusty media. We discuss the astrophysical applications of our results.
646
- CHOI CHUL-SUNG
- Journal of the Korean astronomical society = 천문학회지
- 36, n.2
- pp.73-73
- 2003
- 원문 바로보기
Proof correction to the equation in the third paragraph of the DISCUSSION AND CONCLUSION has not been carried faithfully to the published version of the paper. The corrected equation should read <TEX>${\approx}10^{-3}\;M_8^4/^3(N_{\ast}/10^6\;pc^{-3})({\sigma}/300 km\;s^{-l})^{-l}(r/r_t)\;yr^{-1}$</TEX>, where Ms is the mass of the SMBH in units of <TEX>$10^8\;M_{\bigodot}$</TEX>, <TEX>$\sigma$</TEX> is the virial velocity of the stars, <TEX>$r_t$</TEX> is the tidal radius of the SMBH. This estimates the frequency that a star would pass within a sphere with the radius r from the SMBH, rather than the frequency of the tidal disruption event. Therefore, it increases with the mass of the SMBH. However, the loss cone effect should also be taken into account, which reduces the actual event rate. Here, we adopted a factor of one hundred to consider the deficiency from the isotrophic rate. The authors sincerely regret this error.
647
- PEARSON CHRIS
- Journal of the Korean astronomical society = 천문학회지
- 36, n.3
- pp.249-260
- 2003
- 원문 바로보기
ASTRO-F is the next generation Japanese infrared space mission of the Institute of Space and Astronautical Science. ASTRO-F will be dedicated to an All Sky Survey in the far-infrared in 4 bands from 50-200microns with 2 additional mid-infrared bands at 9microns and 20microns. This will be the first all sky survey in the infrared since the ground breaking IRAS mission almost 20 years ago and the first ever survey at 170microns. The All Sky Survey should detect 10's of millions of sources in the far-infrared bands most of which will be dusty luminous and ultra-luminous star forming galaxies, with as many as half lying at redshifts greater than unity. In this contribution, the ASTRO-F mission and its objectives are reviewed and many of the mission expectations are discussed.
648
- HIEI E.
- Journal of the Korean astronomical society = 천문학회지
- 36, n.suppl1
- pp.45-47
- 2003
- 원문 바로보기
A white light flare was observed at the limb on 16 August 1989 in He 10830 <TEX>${\AA}$</TEX> spectra, H<TEX>$\alpha$</TEX> slit jaw photo-grams, and white light filter-grams of <TEX>${\lambda}=5600{\AA}{\pm}800{\AA}$</TEX>. The kernels of the white light flare are not spatially related with Ha brightenings, suggesting that the flare energy would be released at the photosphere.
649
- SANDERS D. B.
- Journal of the Korean astronomical society = 천문학회지
- 36, n.3
- pp.149-158
- 2003
- 원문 바로보기
Deep surveys at mid-infared through submillimeter wavelengths indicate that a substantial fraction of the total luminosity output from galaxies at high redshift (z > 1) emerges at wavelengths 30 - 300<TEX>${\mu}m$</TEX>. In addition, much of the star formation and AGN activity associated with galaxy building at these epochs appears to reside in a class of luminous infrared galaxies (LIGs), often so heavily enshrouded in dust that they appear as 'blank-fields' in deep optical/UV surveys. Here we present an update on the state of our current knowledge of the cosmic evolution of LIGs from z = 0 to z <TEX>$\~$</TEX> 4 based on the most recent data obtained from ongoing ground-based redshift surveys of sources detected in ISO and SCUBA deep fields. A scenario for the origin and evolution of LIGs in the local Universe (z < 0.3), based on results from multiwavelength observations of several large complete samples of luminous IRAS galaxies, is then discussed.
650
- ANN HONG BAE
- Journal of the Korean astronomical society = 천문학회지
- 36, n.3
- pp.241-248
- 2003
- 원문 바로보기
Owing to several observational evidences and theoretical predictions for morphological evolution of galaxies, it is now widely accepted that galaxies do evolve from late types to early ones along the Hubble sequence. It is also well established that non-axisymmetric potentials of bar-like or oval mass distributions can change the morphology of galaxies significantly during the Hubble time. Here, we review the observational and theoretical grounds of the secular evolution driven by bar-like potentials, and present the results of SPH simulations for the response of the gaseous disks to the imposed potentials to explore the secular evolution in the central regions of barred galaxies.