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- 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
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1021
BLUE STRAGGLERS, CATACLYSMIC VARIABLES, X-RAY BINARIES, AND MILLISECOND PULSARS IN GLOBULAR CLUSTERS
- Lee, Hyung-Mok
- 天文學會誌 = The journal of the Korean Astronomical Society
- 25, n.1
- pp.47-64
- 1992
- 원문 바로보기
Cores of globular clusters are an ideal place for close encounters between stars. The outcome of tidal capture can be stellar mergers, close binaries between normal stars (W UMa type), cataclysmic variables composed of white dwarf and normal star pairs, or low-mass X-ray binaries consisting of a neutron star and a normal star pairs. Stellar mergers can be the origin of blue stragglers in dense globular clusters although they are hard to observe. Low mass X-ray binaries would eventually become binary pulsars with short pulse periods after the neutron stars accrete sufficient amount of matter from the companion. However, large number of recently discovered, isolated millisecond pulsars (as opposed to binary pulsars) in globular clusters may imply that they do not have to gain angular speeds during the X-ray binary phase. We propose that these isolated millisecond pulsars may have formed through the disruptive encounters, which lead to the formation of accretion disk without Roche lobe filling companion, between a neutron star and a main-sequence star. Based on recently developed multicomponent models for the dynamical evolution of globular clusters, we compute the expected numbers of various systems formed by tidal capture as a function of time.
1022
- La, Daile
- 天文學會誌 = The journal of the Korean Astronomical Society
- 25, n.2
- pp.105-109
- 1992
- 원문 바로보기
We show that spacing patterns of planets and satellites in the solar system are formulatable in a single form. It is suggested that a possible explanation for the rule might be the orbital resonance effect, which has existed at an earlier epoch of the solar (planet) system. By extrapolating the formulated spacing patterns beyond the sun-Pluto distance, we find the sun-Planet X distance falls in a range (<TEX>$46{\sim}79$</TEX>) A. U..
1023
- Chang, Kyong-Ae
- 天文學會誌 = The journal of the Korean Astronomical Society
- 25, n.2
- pp.79-90
- 1992
- 원문 바로보기
The physical properties of the flux factor K and its application are discussed in connection to the high amplification events. The effects due to random motions of stars in a foreground galaxy are examined in the frame work of moving caustics of gravitational microlenses.
1024
- Sung, Hwan-Kyung
- 天文學會誌 = The journal of the Korean Astronomical Society
- 25, n.2
- pp.91-104
- 1992
- 원문 바로보기
New photoelectric UBV Photometry of 112 stars in open cluster M35 field was obtained. The distance modulus and age of the cluster are <TEX>$9.^m3$</TEX>(725pc) and <TEX>$8.5{\times}10^7yrs$</TEX>, respectively. The internal differential reddening within the cluster is apparent.
1025
- Oh, K.S.
- 天文學會誌 = The journal of the Korean Astronomical Society
- 25, n.1
- pp.1-9
- 1992
- 원문 바로보기
We present new approach to analysis of velocity data of globular clusters. Maximum likelihood method is applied to get model parameters such as central potential, anisotropy radius, and total mass fractions in each mass class. This method can avoid problems in conventional binning method of chi-square. We utilize three velocity components, one from line of sight radial velocity and two from proper motion data. In our simplified scheme we adopt 3 mass-component model with unseen high mass stars, intermediate visible stars, and low mass dark remnants. Likelihood values are obtained for 124 stars in M13 for various model parameters. Our preferred model shows central potential of <TEX>$W_o=7$</TEX> and anisotropy radius with 7 core radius. And it suggests non-negligible amount of unseen high mass stars and considerable amount of dark remnants in M13.
1026
- Park, Y.S.
- 天文學會誌 = The journal of the Korean Astronomical Society
- 25, n.2
- pp.67-78
- 1992
- 원문 바로보기
Effects of cloud rotation 011 the profiles of CO J=<TEX>$1{\rightarrow}0$</TEX> lines arc investigated by theoretically general ing line profiles under physical conditions similar to t he ones in large globules. The synthesized profiles are presented and their characteristics are discussed. It is found that when the Doppler shift of the observed CO lines is interpreted as the rotation velocity, the optically thin <TEX>$^{13}CO$</TEX> lines underestimate the rotation velocity by up to 10 percents, while the self-reversed optically thick <TEX>$^{12}CO$</TEX> lines overestimate the velocity up to 20 percents. The optically thin line is shown to be of use in probing the distribution of rotation velocity in dark globules.
1027
- Sohn, Young-Jong
- 天文學會誌 = The journal of the Korean Astronomical Society
- 24, n.2
- pp.151-159
- 1991
- 원문 바로보기
Using the photographic imagery of the SO galaxy NGC 5102, the equivalent luminosity profile and the fractional integrated luminosity curve have been derived. Several photometric parameters of the galaxy, such as a total magnitude (<TEX>$B_T$</TEX>), equivalent radius (<TEX>$r^*_e$</TEX>), effective surface brightness (<TEX>${\mu}^*_e$</TEX>), and concentration indices (<TEX>$C_{21}$</TEX>, <TEX>$C_{32}$</TEX>) were derived from the luminosity profiles. According to the decomposition method from the nonlinear least squares fitting, photometric parameters of the bulge (<TEX>${\mu}_e$</TEX>, <TEX>$r_e$</TEX>) and the exponential disk (<TEX>${\mu}(0)$</TEX>, <TEX>${\alpha}^{-1}$</TEX>), and the bulge to total luminosity ratio (B/T) were obtained. The derived central disk surface brightness (<TEX>${\mu} (0)\;=\;22.06\;{\pm}\;0.18\;mag/\Box'$</TEX>) and the evaluated B/T ratio (= 0.52) of the NGC 5102 are close to the mean values (<TEX>${\mu} (0)\;=\;21.65\;{\pm}\;0.3\;mag/\Box'$</TEX>, B/T=0.63) of the SO galaxies. Analysis showed that a lens-like hump is embedded in the equivalent luminosity profile of the NGC 5102.
1028
- Kim, K.T.
- 天文學會誌 = The journal of the Korean Astronomical Society
- 24, n.1
- pp.95-105
- 1991
- 원문 바로보기
In the presence of synchrotron losses, diffusion of an ensembel of relativistic particles in an intraculster medium is investigated. The diffusion coefficient in the medium is found to be constrained by <TEX>$28.8\;{\pm}\;0.4\;{\leq}\;Log\;D\;{\leq}\;30.5\;{\pm}\;0.4\;cm^2s^{-1}$</TEX> with the energy dependency of <TEX>$D_0{\varepsilon}^{\mu}$</TEX> of <TEX>${\mu}=0.4{\pm}0.2$</TEX> as the previous observations suggested. As an important implication of the result, the brightest head-tail radio source NGC 4869, whose radio tail structure is indicative for its orbit within the cluster core, is considered to be the major contributor of particles for the formation of the Coma radio halo.
1029
- Ann, Hong-Bae
- 天文學會誌 = The journal of the Korean Astronomical Society
- 24, n.1
- pp.13-24
- 1991
- 원문 바로보기
We construct a simple photometric evolution model of galaxies based on the evolutionary population synthesis. In our models an exponentially decreasing SFR with a power law IMF is used to compute the UBV colors of galaxies from ellipticals to late type spirals. It is shown that the integrated colors of galaxies with different Hubble type can be explained by one parameter, SFR.
1030
- Hong, S.S.
- 天文學會誌 = The journal of the Korean Astronomical Society
- 24, n.1
- pp.71-94
- 1991
- 원문 바로보기
With the 14 m radio telescope at DRAO and the 4 m at Nagoya University, we have made detailed maps of <TEX>$^{12}CO$</TEX> and <TEX>$^{13}CO$</TEX> emissions from two Barnard objects B133 and B134 in the <TEX>$J=1{\rightarrow}O$</TEX> rotational transition lines. Usual LTE analyses of the CO observations led us to determine the distribution of column densities over an entire area encompassing both globules. Total gas masses estimated from the column density map are <TEX>$90\;M_{\odot}$</TEX> and <TEX>$20\;M_{\odot}$</TEX> for B133 and B134, respectively. The radial velocity of B133 is red shifted with respect to B134 by <TEX>$0.8\;km\;s^{-1}$</TEX>, which is too lagre to bind the two clouds as a binary system. We have shown that the usual stability analysis based on the simplified version of virial theorem with the second time-derivative of the moment of inertia term <TEX>$\ddot{I}$</TEX> being ignored could mislead us in determining whether a given cloud eventually collapses or not. The lull version of the scalar virial theorem with the <TEX>$\ddot{I}$</TEX> term is shown to be useful in following up the time-dependent variations of the cloud size R and its streaming velocity <TEX>$\dot{R}$</TEX> as functions of time. Results of our stability analysis suggest that B133 will eventually collapse in <TEX>$(2{\sim}4){\times}10^6$</TEX> years.