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- 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 82/122
811
- LEE HYUN-CHUL
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.133-134
- 1996
- 원문 바로보기
We present the systematic variations of H<TEX>$\beta$</TEX> index of simple stellar populations due to horizontal-branch (HB) stars. Most of the previous works have been done without careful considerations of HB stars. Since the Balmer line strengths are very sensitive to the temperature, including the HB stars are quite important. We found that the strength of H,6 index is strongly affected by HB stars, and hence the age estimation without careful consideration of the variation of HB morphology with metallicity and age would underestimate the ages of ellipticals.
812
- ZHOU WENGE
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.403-404
- 1996
- 원문 바로보기
This paper describes a plan of a new IR phace-shfting interferometric system for testing astronomical aspheric mirror which has big departure from the best fit reference sphere during fine grinding. In this experimental system, some new technology will be adopted. The accuracy of system can reach <TEX>$\lambda$</TEX>/40(<TEX>$\lambda$</TEX>=10.6<TEX>${\mu}m$</TEX>)
813
- LEE SANG WOO
- Journal of the Korean astronomical society = 천문학회지
- 29, n.1
- pp.9-18
- 1996
- 원문 바로보기
We have analyzed vector magnetograms and <TEX>$H\beta$</TEX> filtergrams of two sunspot groups, one in a growing phase and the other in a decaying phase. In this study, the temporal evolution of their magnetic morphology has been investigated in association with solar activity. The morphological variations of the growing and decaying phase of these sunspots revealed in detail the coalescence of small spots into a large spot and the fragmentation of a large spot into many small spots, respectively. Numerous small flares were detected in the spot group during the decaying phase. This seems to be intimately associated with the shearing motions of many spots with different polarities created by fragmentation of a large sunspot. The magnetic flux and the average shear angle are found to be substantially reduced during the decaying phase, especially in the course of the flarings. This implies that the decaying phase of the sunspot is, to some degree, involved with magnetic field cancellation. The growing spot group has not shown any large activities, but numerous small spots have grown into a typical bipolar sunspot.
814
- XIAO K. C.
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.413-414
- 1996
- 원문 바로보기
A 230 GHz SIS tunnel junction receiver has been being developed for radio astronomy in Nagoya University. In this heterodyne receiver, we use a <TEX>$\~$</TEX>1/3 reduced hight rectangular waveguide SIS mixer with two tuning elements as front end. The mixer block with SIS junction was cooled to 4K with a closed cycle He-gas refrigerator. So far, a double sideband receiver noise temperature lower than l00K in 222-237 GHz is obtained. The receiver exhibits a best DSB noise temperature of 69K at 236 GHz as well as 228 GHz.
815
- YUAN CHI
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.45-48
- 1996
- 원문 바로보기
Rings are common in disk galaxies. These rings are either indistinguishable from a pair of tightly wound spirals, or themselves are a part of the spiral structure. Furthermore, their occurrence is seen coincident with a bar in the center. In this paper, we interpret this spiral-ring structure as density waves resonantly excited by a rotating bar potential. The theory gives excellent agreement for the molecular spiral-rings in central parts. of nearby disk galaxies, observed by high resolution radio arrays. The same mechanism works for more distant spiral-rings in the outer parts of disk galaxies qualitatively, although the problem is complicated by the coupling of the stellar and gaseous disks.
816
- FATEMI S. J.
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.57-58
- 1996
- 원문 바로보기
There is an excess gamma flux from the general direction of the Galactic North Pole compared with that from the south when allowance is made for the contribution from CR interactions with the HI gas (Osborne et al., 1994). The extent to which it is in accord with the predictions of Wdowczyk and Wolfendale (1990 a,b) for gamma rays secondary to very high energy CR escaping from the VIRGO cluster is examined and it is claimed that the observations may well be of the order of those expected.
817
- LEE YOUNGUNG
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.187-188
- 1996
- 원문 바로보기
We have mapped <TEX>$1 deg^2$</TEX> region toward a high latitude HII region S73 (l, b) = (<TEX>$37^{\circ}.69$</TEX>, <TEX>$44^{\circ}.55$</TEX>) and associated molecular cloud in <TEX>$^{12}CO$</TEX> J = 1 - 0, and <TEX>$^{13}CO$</TEX> J = 1 - 0, using the 3 mm SIS receiver on the 14 m telescope at Taeduk Radio Astronomy Observatory. A high resolution autocorrelator is used to resolve extremely narrow CO linewidths (FWHP < 1 km/s) of the molecular cloud. Though the linewidths are very narrow, it is found that there is systematic velocity gradient in the molecular gas associated with the H II region. Both of <TEX>$^{12}CO$</TEX> and <TEX>$^{13}CO$</TEX> averaged spectra are non-gaussian, and there are obvious blue wings in the spectra. It is remarkable that the linewidths at the blueshifted region are broader than those of the rest of the cloud. The CO emission does match well with the dust emission.
818
- HU HUI
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.255-256
- 1996
- 원문 바로보기
819
- OKAMURA S.
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.375-378
- 1996
- 원문 바로보기
An outline is given of our development of mosaic CCD cameras. Hardware and data reduction software of two operational cameras are described. Scientific objectives of wide-field imaging with the cameras are briefly described.
820
- TOHMURA ICHIROH
- Journal of the Korean astronomical society = 천문학회지
- 29, n.suppl1
- pp.333-335
- 1996
- 원문 바로보기
Here we report the results from spectroscopic observations of soloar active regions in the HeI 10830 <TEX>${\AA}$</TEX> line at the German Vacuum Tower Telescope(VTT) in Tenerife during the August 199:3 International EFR(Emerging Flux Region) Campaign. Four active regions in various stages of their evolution, i.e., NOAA7558, 7560, 7561, and 7562, were ovserved on 10 August 1993. From the observed HeI 10830 <TEX>${\AA}$</TEX> spectra in these active regions, spectroscopic quantities such as equivalent width(EW), doppler shift, doppler width, etc., were derived(see Figure l(a)) and the correlation between them were studied(see Figure l(b)). Our main results are as follows: (I)In NOAA7562, which is a young and evolving EFR, the EW is large, while it is small around a simple and roundish spot of NOAA7558. (2)In these active regions, redshift in the 10830 line is dominant when the EW is larger. (3)As the doppler width increases, the line tends to shift redward. (4)When the EW is smaller, it seems to exist another component which have dynamic characteristics different from the redshifting component. In NOAA7560 and NOAA7561, regions which have several small spots, the values of the EW are intermediate. Results (2) and (3) may suggest the possible existence of downflow above active regions, if the HeI 10830 <TEX>${\AA}$</TEX>line is formed in the upper chromopshere, and it is consistent with the earlyer result from the SMM extreme-ultraviolet observation by Klimchuk(1987, Astrophys. J., 323, 368) (to be submitted. to Astronomy and Astrophysics; an extended abstract)