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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 49/122
481
- SHEN ZHI-QIANG
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.261-266
- 2005
- 원문 바로보기
This paper reviews the progress in the VLBI (Very Long Baseline Interferometry) studies of Sgr A<TEX>$\ast$</TEX>, the best known supermassive black hole candidates with a dark mass concentration of <TEX>$4 {\times} 10^6 M_{\bigodot}$</TEX> at the center of the Milky Way. The emphasis is on the importance of the millimeter and sub-millimeter VLBI observations in the detection of Sgr A<TEX>$\ast$</TEX>'s intrinsic structure and search for the structural variation.
482
- SATO BUN'EI
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.315-318
- 2005
- 원문 바로보기
We have carried out a precise Doppler survey of G-type giants aiming to unveil the properties of planetary systems in intermediate-mass stars (<TEX>$1.5-5M_{\bigodot}$</TEX>). G-type giants are promising targets for Doppler planet searches around massive stars, because they are slow-rotators and have many sharp absorption lines in their spectra and their surface activities are relatively low in contrast to their younger counterparts on the main-sequence (B-A stars). We are now monitoring radial velocities of about 300 late G-type (including early K-type) giants using HIgh Dispersion Echelle Spectrograph (HIDES) at Okayama Astrophysical Observatory. We have achieved a Doppler precision of about 6-7 m/s over a time span of 3 years using an iodine absorption cell. We found that most of the targets have radial velocity scatters of <TEX>${\sigma}{\~} 10-20 m\;s^{-1}$</TEX> over 1-3 years, with the most stable reaching levels of 6-8 m <TEX>$s^{-1}$</TEX>. Up to now, we have succeeded in discovering the first extrasolar planet around a G-type giant star HD 104985, and also found several candidates showing significant radial velocity variations, suggesting the existence of stellar and substellar companions. Observations have continued to establish their variability.
483
- WANG Z.R.
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.289-290
- 2005
- 원문 바로보기
The 6th East Asian Meeting of Astronomy was held just at the time of 400 years after the discovery of SN (supernova) 1604 and its pre-maximum observation by the astronomers both from the East and the West in the 17th century. It has a special meaning and is interesting to look back on the historical observation of SN 1604. In this paper, we only limit to concern the Chinese observation on SN 1604.
484
- LIM JEREMY
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.237-240
- 2005
- 원문 바로보기
We present images of L1551 IRS5 at angular resolutions as high as <TEX>${\~}$</TEX>30 mas, corresponding to a spatial resolution of <TEX>${\~}$</TEX>5 AU, made at 7 mm with the VLA. Previously known to be a binary protostellar system, we show that L1551 IRS5 is likely a triple protostellar system. The primary and secondary components have a projected separation of <TEX>${\~}$</TEX>46 AU, whereas the tertiary component has a projected separation of <TEX>${\~}$</TEX>11 AU from the primary component. The circumstellar dust disks of the primary and secondary components have dimensions of <TEX>${\~}$</TEX>15 AU, whereas that of the tertiary component has a dimension of <TEX>${\~}$</TEX>10 AU. Their major axes are closely, but not perfectly, aligned with each other, as well as the major axis of the surrounding flattened, rotating, and contracting molecular condensation (pseudodisk). Furthermore, the orbital motion of the primary and secondary components is in the same direction as the rotational motion of this pseudodisk. We suggest that all three protostellar components formed as a result of the fragmentation of the central region of the molecular pseudo disk. The primary and secondary components, but apparently not the tertiary component, each exhibits a bipolar ionized jet that is centered on and which emergers perpendicular to its associated dust disk. Neither jets are resolved along their base, implying that they are driven within a radial distance of <TEX>${\~}$</TEX>2.5 AU from their central protostars. Finally, we show evidence for what may be dusty matter streams feeding the two main protostellar components.
485
- UMETSU KEIICHI
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.191-195
- 2005
- 원문 바로보기
We used Subaru observations of A1689 (z = 0.183) to derive an accurate, model-independent mass profile for the entire cluster, r<TEX>$\le$</TEX>2Mpc/h, by combining magnification bias and distortion measurements. The projected mass profile steepens quickly with increasing radius, falling away to zero at r<TEX>${\~}$</TEX>1.0Mpc/h, well short of the anticipated virial radius. Our profile accurately matches onto the inner profile, r <TEX>$\le$</TEX>200kpc/ h, derived from deep HST / ACS images. The combined ACS and Subaru information is well fitted by an NFW profile with virial mass, <TEX>$(1.93 \pm 0.20) {\times}10^{15} M_{\bigodot}$</TEX>, and surprisingly high concentration, <TEX>$C_{vir} = 13.7^{+1.4}_{-1.1}$</TEX>, significantly larger than theoretically expected (<TEX>$C_{vir} {\le}4$</TEX>), corresponding to a relatively steep overall profile. These results are based on a reliable sample of background galaxies selected to be redder than the cluster E/SO sequence. By including the faint blue galaxy population a much smaller distortion signal is found, demonstrating that blue cluster members significantly dilute the true signal for r <TEX>$\le$</TEX> 400kpc/ h. This contamination is likely to affect most weak lensing results to date.
486
- ZHOU Xu
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.203-206
- 2005
- 원문 바로보기
The large field multi-color CCD sky survey program based on the 60/90 Schmidt telescope of NAOC has been processed in cooperation among many observatories and universities of Asian countries. The observation and scientific results are reviewed.
487
- YUAN CHI
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.197-201
- 2005
- 원문 바로보기
It is well known that a rotating bar potential can transport angular momentum to the disk and hence cause the evolution of the disk. Such a process is particularly important in disk galaxies since it can result in fuelling AGNs and starburst ring activities. In this paper, we will present the numerical simulations to show how this mechanism works. The problem, however, is quite complicated. We classify our simulations according to the type of Lindbald resonances and try to single out the individual roles they play in the disk evolution. Among many interesting results, we emphasize the identification of the origin of the starburst rings and the dense circumnuclear molecular disks to the instability of the disk. Unlike most of the other simulations, the self-gravitation of the disk is emphasized in this study.
488
- CHUNG EUN JUNG
- Journal of the Korean astronomical society = 천문학회지
- 38, n.1
- pp.17-22
- 2005
- 원문 바로보기
In this paper, we suggest a new referencing method for the array On-The-Fly(OTF) observations in radio astronomy. To reduce the baseline residual, we have proposed and evaluated a new referencing method which uses the source free regions in the observed frame as references. These new references have small <TEX>${\Delta}$</TEX>t and <TEX>${\Delta}$</TEX>x, the time and position differences between the source and the references, and the systematic problems w~re improved by using this new referencing method. The curved baseline residuals were straightened and the rms was reduced to 17 mK. This new referencing method is expected not only to make possible to take more stable data for the array OTF observation of external galaxies but also to save the observation and data reduction time.
489
- KANG MEEJOO
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.33-41
- 2005
- 원문 바로보기
We have conducted observations toward the molecular cloud associated with the H II region Sh 156 in <TEX>$^{13}CO$</TEX>(J = 1-0), <TEX>$C^{18}O$</TEX>(J = 1-0), and CS(J = 2 -1) using the TRAO 14 m telescope. Combining with existing <TEX>$^{12}CO$</TEX>(J = 1- 0) data of the Outer Galaxy Survey, we delineated the physical properties of the cloud. We found that there is a significant sign of interaction between the H II region and the molecular gas. We estimated the masses of the molecular cloud, using three different techniques; the most plausible mass is estimated to be <TEX>$1.37 {\times} 10^5 M_{\bigodot}$</TEX>, using a conversion factor of <TEX>$X = 1.9 {\times} 10^{20}\;cm^{-2} (K\;km\;s^{-1})^{-1}$</TEX>, and this is similar to virial mass estimate. This implies that the cloud is gravitationally bound and in virial equilibrium even though it is closely associated with the H II region. In addition to existing outflow, we found several MSX and IRAS point sources associated with dense core regions. Thus, more star forming activities other than the existing H II region are also going on in this region.
490
- AWADALLA N. S.
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.43-57
- 2005
- 원문 바로보기
The authors have assembled a sample of 80 W UMa binary systems (42 W-subtype and 38 A-subtype) whose light curves have all been solved by means of the recent W-D code and combined with up-to-date radial velocity solutions. The absolute parameters (masses, radii and luminosities) have been derived (without any constraint on the physical parameters). The main results of this paper are: (1) the mass-luminosity relations for both W&A-subtypes. as well as for all W UMa contact binaries have been shown, (2) the mass-radius relations have been found for both subtypes, (3) some remarks on the evolution status have been presented.