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Sodium content as a predictor of the advanced evolution of globular cluster stars

机译：钠含量可预测球状星团高级演化

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摘要

The asymptotic giant branch (AGB) phase is the final stage of nuclear burning for low-mass stars. Although Milky Way globular clusters are now known to harbour (at least) two generations of stars, they still provide relatively homogeneous samples of stars that are used to constrain stellar evolution theory. It is predicted by stellar models that the majority of cluster stars with masses around the current turn-off mass (that is, the mass of the stars that are currently leaving the main sequence phase) will evolve through the AGB phase. Here we report that all of the second-generation stars in the globular cluster NGC 6752—70 per cent of the cluster population—fail to reach the AGB phase. Through spectroscopic abundance measurements, we found that every AGB star in our sample has a low sodium abundance, indicating that they are exclusively first-generation stars. This implies that many clusters cannot reliably be used for star counts to test stellar evolution timescales if the AGB population is included. We have no clear explanation for this observation.
机译：渐近巨型分支（AGB）阶段是低质量恒星燃烧核的最后阶段。尽管现在已知银河系球状星团包含（至少）两代恒星，但它们仍提供了相对均匀的恒星样本，用于约束恒星演化理论。通过恒星模型可以预测，质量围绕当前关闭质量（即当前离开主序相的恒星质量）周围的大多数簇状恒星将通过AGB阶段演化。在这里，我们报告说，球状星团NGC 6752中的所有第二代恒星（占星团总数的70％）未能达到AGB阶段。通过光谱丰度测量，我们发现样本中的每个AGB恒星都具有较低的钠丰度，表明它们仅是第一代恒星。这意味着，如果包括AGB种群，则无法将许多星团可靠地用于恒星计数以测试恒星演化的时标。我们对此观察没有明确的解释。

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  • 来源
    《Nature》 |2013年第7453期|198-200|共3页
  • 作者

    Simon W. Campbell; Valentina DOrazi; David Yong; Thomas N. Constantino; John C. Lattanzio; Richard J. Stancliffe; George C. Angelou; Elizabeth C. Wylie-de Boer; Frank Grundahl;

  • 作者单位

    Monash Centre for Astrophysics, School of Mathematical Sciences, Monash University, Melbourne, Victoria 3800, Australia;

    Monash Centre for Astrophysics, School of Mathematical Sciences, Monash University, Melbourne, Victoria 3800, Australia,Department of Physics and Astronomy, Macquarie University, Balaclava Road,North Ryde, Sydney, New South Wales 2109, Australia;

    Research School of Astronomy and Astrophysics, Australian National University, Weston, Australian Capital Territory 2611, Australia;

    Monash Centre for Astrophysics, School of Mathematical Sciences, Monash University, Melbourne, Victoria 3800, Australia;

    Monash Centre for Astrophysics, School of Mathematical Sciences, Monash University, Melbourne, Victoria 3800, Australia;

    Research School of Astronomy and Astrophysics, Australian National University, Weston, Australian Capital Territory 2611, Australia,Argelander-Institut fuer Astronomie, Universitaet Bonn, Auf dem Huegel 71, 53121 Bonn, Germany;

    Monash Centre for Astrophysics, School of Mathematical Sciences, Monash University, Melbourne, Victoria 3800, Australia;

    Research School of Astronomy and Astrophysics, Australian National University, Weston, Australian Capital Territory 2611, Australia;

    Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 1, DK-8000 Aarhus C, Denmark;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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