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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 32/122
311
- Le, Huynh Anh Nguyena
- Journal of the Korean astronomical society = 천문학회지
- 44, n.4
- pp.125-134
- 2011
- 원문 바로보기
We present medium resolution (R = 5000 - 6000) spectra in the near-infrared band, 1.4 - 1.8 <TEX>${\mu}m$</TEX>, for template stars in G, K, and M types observed by the echelle spectrometer, IRCS, at the SUBARU 8.2 m telescope. The identification of lines is based on the spectra of Arcturus (K2 III) in the literature. We measured the equivalent of widths and compared our results to those of Meyer et al. (1998). We conclude that our spectral resolution (R = 6000) data can investigate more accurately the properties of lines in stellar spectra. The library of the template stellar spectra in ASCII format are available for download on the World Wide Web.
312
- Ann, Hong-Bae
- Journal of the Korean astronomical society = 천문학회지
- 44, n.1
- pp.23-32
- 2011
- 원문 바로보기
We present a deep CCD imaging in B and V bands which allows us to analyze the vertical structure of NGC 4631. We derive the scale heights of the thin and thick disks at a variety of positions along the major axis of the disk. The scale heights of the thin disk are nearly constant while those of the thick disk tend to increase with increasing galactocentric distance. The mean scale heights of the thin disk derived from B and V images are similar to each other (~ 450 pc). Instead, those of the thick disk show a strong east-west asymmetry which is caused by the diffuse stellar emission that is most prominent in the north west regions above the disk plane. The ratio of scale heights (<TEX>$z_{thick}/z_{thin}$</TEX>) is about 2.5 in the east side of the disk. However, this ratio is greater than 4 for the thick disk above the disk plane in the west side of the galaxy.
313
HALF-TURN ROTATION OF A POLARITY INVERSION LINE AND ASSOCIATED QUADRUPOLAR-LIKE STRUCTURE IN THE SUN
- Magara, Tetsuya
- Journal of the Korean astronomical society = 천문학회지
- 44, n.5
- pp.143-150
- 2011
- 원문 바로보기
This paper reports a characteristic motion of a polarity inversion line (PIL) formed at the solar surface, which is newly found by performing a three-dimensional magnetohydrodynamic simulation of flux emergence in the Sun. A magnetic flux tube composed of twisted field lines is assumed to emerge below the surface, forming a bipolar region with a PIL at the surface. A key finding is the successive half-turn rotation of the PIL, leading to the formation of a quadrupolar-like region at the surface and a magnetic configuration in the corona; this configuration is reminiscent of, but essentially different from the so-called inverse-polarity configuration of a filament magnetic field. We discuss a physical mechanism for producing the half-turn rotation of a PIL, which gives new insights into the magnetic structure formed via flux emergence. This presents a reasonable explanation of the configuration of a filament magnetic field suggested by observations.
314
- Kim, Ji-Hoon
- Journal of the Korean astronomical society = 천문학회지
- 44, n.5
- pp.151-160
- 2011
- 원문 바로보기
We present a study searching for globular cluster systems (GCSs) of two face-on low surface bright- ness galaxies (LSBGs), UGC 5981 and UGC 6614. Based on HSTWFPC2 images of F555Wand F814W filters, we detect 12 and 18 GC candidates for UGC 5981 and UGC 6614, respectively. Although these two LSBGs have very different bulge properties, they have very similar specific frequencies (<TEX>$S_N$</TEX>) of 0.1. However, <TEX>$S_N$</TEX> ~ 0.1 is quite small even for their late morphological types, albeit within errors. This suggests that LSBGs have had star formation histories lacking dominant initial starburst events while accumulating their stellar masses through sporadic star formation activities.
315
- Lee, Jeong-Eun
- Journal of the Korean astronomical society = 천문학회지
- 44, n.2
- pp.67-72
- 2011
- 원문 바로보기
We report the results of our high resolution optical spectroscopic monitoring campaign (<TEX>${\lambda}$</TEX> = 3800 ~ 8800 <TEX>${\AA}$</TEX>, R = 30000 - 45000) of the new FU Orionis-type object HBC 722. We observed HBC 722 with the BOES 1.8-m telescope between November 26 and December 29, 2010, and FU Orionis itself on January 26, 2011. We detect a number of previously unreported high-resolution K I and Ca II lines beyond 7500 <TEX>${\AA}$</TEX>. We resolve the H<TEX>${\alpha}$</TEX> and Ca II line profiles into three velocity components, which we attribute to both disk and outflow. The increased accretion during outburst can heat the disk to produce the relatively narrow absorption feature and launch outflows appearing as high velocity blue and red-shifted broad features.
316
- Tadross, A.L.
- Journal of the Korean astronomical society = 천문학회지
- 44, n.1
- pp.1-11
- 2011
- 원문 바로보기
A sample of 145 JHK-2MASS observations of NGC open star clusters is studied, of which 132 have never been studied before. Twelve are classified as non-open clusters and 13 are re-estimated self-consistently, after applying the same methods in order to compare and calibrate our reduction procedures. The fundamental and structural parameters of the 120 new open clusters studied here are derived using color-magnitude diagrams of JHK Near-IR photometry with the fitting of solar metallicity isochrones. We provide here, for the first time, a catalog of the main parameters for these 120 open clusters, namely, diameter, distance, reddening and age.
317
- Choi, Isaac Yeoun-Gyu
- Journal of the Korean astronomical society = 천문학회지
- 44, n.5
- pp.161-175
- 2011
- 원문 바로보기
We examine the dependence of the morphology of spiral galaxies on the environment using the KIAS Value Added Galaxy Catalog (VAGC) which is derived from the Sloan Digital Sky Survey (SDSS) DR7. Our goal is to understand whether the local environment or global conditions dominate in determining the morphology of spiral galaxies. For the analysis, we conduct a morphological classification of galaxies in 20 X-ray selected Abell clusters up to z~0.06, using SDSS color images and the X-ray data from the Northern ROSAT All-Sky (NORAS) catalog. We analyze the distribution of arm classes along the clustercentric radius as well as that of Hubble types. To segregate the effect of local environment from the global environment, we compare the morphological distribution of galaxies in two X-lay luminosity groups, the low-<TEX>$L_x$</TEX> clusters (<TEX>$L_x$</TEX> < <TEX>$0.15{\times}10^{44}$</TEX>erg/s) and high-<TEX>$L_x$</TEX> clusters (<TEX>$L_x$</TEX> > <TEX>$1.8{\times}10^{44}$</TEX>erg/s). We find that the morphology-clustercentric relation prevails in the cluster environment although there is a brake near the cluster virial radius. The grand design arms comprise about 40% of the cluster spiral galaxies with a weak morphology-clustercentric radius relation for the arm classes, in the sense that flocculent galaxies tend to increase outward, regardless of the X-ray luminosity. From the cumulative radial distribution of cluster galaxies, we found that the low-<TEX>$L_x$</TEX> clusters are fully virialized while the high-<TEX>$L_x$</TEX> clusters are not.
318
- Lee, Hee-Won
- Journal of the Korean astronomical society = 천문학회지
- 44, n.2
- pp.59-65
- 2011
- 원문 바로보기
A small number of active galactic nuclei are known to exhibit prominent double peak emission profiles that are well-fitted by a relativistic accretion disk model. We develop a Monte Carlo code to compute the linear polarization of a double peaked broad emission line arising from Thomson scattering. A Keplerian accretion disk is adopted for the double peak emission line region and the geometry is assumed to be Schwarzschild. Far from the accretion disk where flat Minkowski geometry is appropriate, we place an azimuthally symmetric scattering region in the shape of a spherical shell sliced with <TEX>${\Delta}{\mu}=0.1$</TEX>. Adopting a Monte Carlo method we generate line photons in the accretion disk in arbitrary directions in the local rest frame and follow the geodesic paths of the photons until they hit the scattering region. The profile of the polarized flux is mainly determined by the relative location of the scattering region with respect to the emission source. When the scattering region is in the polar direction, the degree of linear polarization also shows a double peak structure. Under favorable conditions we show that up to 0.6% linear polarization may be obtained. We conclude that spectropolarimetry can be a powerful probe to reveal much information regarding the accretion disk geometry of these active galactic nuclei.
319
- Choi, Min-Ho
- Journal of the Korean astronomical society = 천문학회지
- 44, n.5
- pp.201-208
- 2011
- 원문 바로보기
The NGC 1333 IRAS 4B region is observed in the 6.9 mm and 1.3 cm continuum with an angular resolution of about 0.4 arcseconds. IRAS 4BI is detected in both bands, and BII is detected in the 6.9 mm continuum only. The 1.3 cm source of BI seems to be a disk-like flattened structure with a size of about 50 AU. IRAS 4BI does not show any sign of multiplicity. Examinations of archival infrared images show that the dominating emission feature in this region is a bright peak in the southern outflow driven by BI, corresponding to the molecular hydrogen emission source HL 9a. Both BI and BII are undetectable in the mid-IR bands. The upper limit on the far-IR flux of IRAS 4BII suggests that it may be a very low luminosity young stellar object.
320
- Ryu, Jin-Hyuk
- Journal of the Korean astronomical society = 천문학회지
- 44, n.5
- pp.177-193
- 2011
- 원문 바로보기
We present a photometric study of five open clusters (Czernik 5, Alessi 53, Berkeley 49, Berkeley 84, and Pfleiderer 3) in the Sloan Digital Sky Survey. The position and size of these clusters are determined using the radial number density profiles of the stars, and the member stars of the clusters are selected using the proper motion data in the literature. We estimate the reddening, distance and age of the clusters based on the isochrone fitting in the color-magnitude diagram. The foreground reddenings for these clusters are estimated to be E(B - V ) = 0.71 - 1.55 mag. The distances to these clusters are derived to be 2.0 - 4.4 kpc, and their distances from the Galactic center range from 7.57 kpc to 12.35 kpc. Their ages are in the range from 250 Myr to 1 Gyr. Berkeley 49 and Berkeley 84 are located in the Orion spur, Czernik 5 is in the Perseus arm, and Pfleiderer 3 and Alessi 53 are located beyond the Perseus arm.