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Frank Grundahl

A WFC3/HST View of the Three Stellar Populations in the Globular Cluster NGC 6752

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  • A. P. Milone, Research School of Astronomy and Astrophysics, The Australian National University, Cotter Road, Weston, ACT, 2611, Australia
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  • A. F. Marino, Research School of Astronomy and Astrophysics, The Australian National University, Cotter Road, Weston, ACT, 2611, Australia
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  • G. Piotto, Dipartimento di Astronomia, Università di Padova, Vicolo dell'Osservatorio 3, Padova I-35122, Italy
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  • L. R. Bedin, INAF-Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, I-35122 Padua, Italy aparicio@iac.es
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  • J. Anderson, Space Telescope Science Institute, 3800 San Martin Drive, Baltimore, MD 21218, USA monelli@iac.es
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  • A. Aparicio, Instituto de Astrofísica de Canarias
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  • A. Bellini, Space Telescope Science Institute, 3800 San Martin Drive, Baltimore, MD 21218, USA luigi.bedin@oapd.inaf.it
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  • S. Cassisi, INAF-Osservatorio Astronomico di Collurania, via Mentore Maggini, I-64100 Teramo, Italy jayander@stsci.edu
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  • F. D'Antona, INAF-Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monte Porzio Catone, Rome, Italy bellini@stsci.edu
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  • F. Grundahl
  • M. Monelli, Instituto de Astrofísica de Canarias
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  • D. Yong, Research School of Astronomy and Astrophysics, The Australian National University, Cotter Road, Weston, ACT, 2611, Australia fgj@phys.au.dk
Multi-band Hubble Space Telescope photometry reveals that the main sequence, sub-giant, and the red-giant branch of the globular cluster NGC 6752 splits into three main components in close analogy with the three distinct segments along its horizontal branch stars. These triple sequences are consistent with three stellar groups: a stellar population with a chemical composition similar to field-halo stars (Population a), a Population (c) with enhanced sodium and nitrogen, depleted carbon and oxygen, and an enhanced helium abundance (ΔY ~ 0.03), and a Population (b) with an intermediate (between Populations a and c) chemical composition and slightly enhanced helium (ΔY ~ 0.01). These components contain ~25% (Population a), ~45% (Population b), and ~30% (Population c) of the stars. No radial gradient for the relative numbers of the three populations has been identified out to about 2.5 half-mass radii. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.
Original languageEnglish
Article number120
JournalAstrophysical Journal
Volume767
Issue2
Number of pages20
ISSN0004-637X
DOIs
Publication statusPublished - 1 Apr 2013

    Research areas

  • globular clusters: individual: NGC 6752, stars: Population II

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