• Title/Summary/Keyword: clusters: open

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Variable Blue Stragglers in the Metal-Poor Globular Clusters in the Large Magellanic Cloud - Hodge 11 and NGC1466

  • Yang, Soung-Chul;Bhardwaj, Anupam
    • The Bulletin of The Korean Astronomical Society
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    • v.46 no.1
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    • pp.35.2-35.2
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    • 2021

  • Blue straggler stars (BSs) are "rejuvenated" main sequence stars first recognized by Allan Sandage from his observation of the prominent northern globular cluster M3 in the year of 1953. BSs are now known to be present in diverse stellar environments including open clusters, globular clusters, dwarf galaxies, and even the field populations of the Milky Way. This makes them a very useful tool in a wide range of astrophysical applications: Particularly BSs are considered to have a crucial role in the evolution of stellar clusters because they affect on the dynamics, the binary population, and the history of the stellar evolution of the cluster they belong to. Here we report a part of the preliminary results from our ongoing research on the BSs in the two metal-poor globular clusters (GCs) in the Large Magellanic Cloud (LMC), Hodge 11 and NGC1466. Using the high precision multi-band images obtained with the Advanced Camera for Survey (ACS) onboard the Hubble Space Telescope (HST), we extract time-series photometry to search for the signal of periodic variations in the luminosity of the BSs. Our preliminary results confirm that several BSs are intrinsic "short period (0.05 < P < 0.25 days)" variable stars with either pulsating or eclipsing types. We will discuss our investigation on the properties of those variable BS candidates in the context of the formation channels of these exotic main sequence stars, and their roles in the dynamical evolution of the host star clusters.

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Galactic Globular and Open Clusters in the Sloan Digital Sky Survey. III. Horizontal Branch Stars and Mass Loss in NGC 6791

  • Yu, Hyein;An, Deokkeun;Chung, Chul
    • The Bulletin of The Korean Astronomical Society
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    • v.39 no.1
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    • pp.61.2-61.2
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    • 2014

  • We present a set of fiducial sequences of horizontal-branch stars in bright Galactic globular clusters, which have previously been observed in the Sloan Digital Sky Survey (SDSS). We derive fiducial lines on color-magnitude diagrams in multiple color indices (g - r, g - i, g - z, and u - g), after rejecting foreground and background objects as well as RR Lyrae variables utilizing these color indices. We compare our fiducial sequences with model predictions from Yonsei-Yale evolutionary tracks and BaSel spectral libraries, and find a satisfactory agreement between them in terms of their color-magnitude relations, except in u - g. We also compare theoretical models to color-magnitude diagrams of two open clusters (M67 and NGC 6791). Based on our best available cluster distance and reddening, we find that the mass of red clump (RC) stars in NGC 6791 is about a factor of two smaller than an earlier estimate from the application of asteroseismic scaling relations for solar-like oscillations. The smaller RC mass implies an enhanced mass loss along the red giant branch, which is in accordance with other compelling evidences found in this metal-rich system. Our estimated luminosity of RC stars in NGC 6791 is about 0.2 mag fainter than in earlier investigations based on solar-metallicity calibrations, and results in ~10% reduction in the RC-based distance estimation, when applied to metal-rich systems such as in the Galactic bulge.

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Effects of Three-Body Interactions on the Stability of Small Carbon Clusters (3체 인력이 탄소 cluster들의 안정도에 미치는 효과)

  • Lee, Jong-Mu
    • Korean Journal of Materials Research
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    • v.1 no.2
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    • pp.86-92
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    • 1991

  • A potential energy function comprising a two-body potential term which is modified form Morse potential and a three-body potential term which is modified from Axilrod-Teller potential has been developed for small carbon clusters. The structural changes of small carbon clusters $C_2-C_6$ are qualitatively investigated by employing this potential energy function representing the energies of the small carbon cluster isotopes as a function of the three body intensity factor. It is found that the structure of the small carbon cluster changes from open structure to closed one, from complicated structure to simple one, and from three-dimensional structure to two-or-one dimensional one as the degree of the three-body interaction increases.

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BINARIES IN OPEN STAR CLUSTERS: PHOTOMETRIC APPROACH WITH APPLICATION TO THE HYADES

  • ALAWY A. EL-BASSUNY;KORANY B. A.;HAROON A. A.;ISMAIL H. A.;SHARAF M. A.
    • Journal of The Korean Astronomical Society
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    • v.37 no.3
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    • pp.119-129
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    • 2004

  • A new method has been developed to solve the star cluster membership problem. It is based on synthetic photometry employing the Black Body concept as stellar radiation simulator. Synthetic color-magnitude diagram is constructed showing the main sequence band and the positions of binary star systems of combinations of various components through different photometric tracks. The method has been applied to the Hyades. The cluster membership problem has been re-appraised for the cluster (both single and binary) stars. For the binary members, the components' spectral types have been derived by the method. The results obtained agree very well with those found in literature, The method is simpler than the others and can be developed to undertake other cases as multiple star systems.

  • https://doi.org/10.5303/JKAS.2004.37.3.119 인용 PDF KSCI