Asteroseismic inferences on red giants in open clusters NGC 6791, NGC 6819, and NGC 6811 using Kepler
- Autor(en)
- S. Hekker, S. Basu, D. Stello, T. Kallinger, F. Grundahl, S. Mathur, R. A. García, B. Mosser, D. Huber, T. R. Bedding, R. Szabó, J. De Ridder, W. J. Chaplin, Y. Elsworth, S. J. Hale, J. Christensen-Dalsgaard, R. L. Gilliland, M. Still, S. McCauliff, E. V. Quintana
- Abstrakt
Context. Four open clusters are present in the Kepler field of view andtimeseries of nearly a year in length are now available. These timeseries allow us to derive asteroseismic global oscillation parameters of red-giant stars in the three open clusters NGC 6791, NGC6819 and NGC 6811. From these parameters and effective temperatures, wederive masses, radii and luminosities for the clusters as well as fieldred giants. Aims: We study the influence of evolution and metallicity on the observed red-giant populations. Methods: Theglobal oscillation parameters are derived using different published methods and the effective temperatures are derived from 2MASS colours.The observational results are compared with BaSTI evolution models. Results: We find that the mass has significant influence on the asteroseismic quantities Δν vs. νmax relation,while the influence of metallicity is negligible, under the assumption that the metallicity does not affect the excitation/damping of the oscillations. The positions of the stars in the H-R diagram depend on both mass and metallicity. Furthermore, the stellar masses derived for the field stars are bracketed by those of the cluster stars. Conclusions: Both the mass and metallicity contribute to the observed difference in locations in the H-R diagram of the old metal-rich cluster NGC 6791 and the middle-aged solar-metallicity cluster NGC 6819. For theyoung cluster NGC 6811, the explanation of the position of the stars inthe H-R diagram challenges the assumption of solar metallicity, and thisopen cluster might have significantly lower metallicity [Fe/H] in therange - 0.3 to - 0.7 dex. Also, nearly all the observed field stars seemto be older than NGC 6811 and younger than NGC 6791.
- Organisation(en)
- Institut für Astrophysik, Bibliotheks- und Archivwesen, Institut für Europäische Ethnologie
- Externe Organisation(en)
- University of Amsterdam (UvA), University of Birmingham, Yale University, The University of Sydney, University of British Columbia (UBC), Aarhus University, National Center for Atmospheric Research (NCAR), Université Paris VII - Paris-Diderot, Université de recherche Paris Sciences et Lettres, Magyar Tudományos Akadémia, Katholieke Universiteit Leuven, Space Telescope Science Institute, National Aeronautics & Space Administration (NASA)
- Journal
- Astronomy & Astrophysics
- Band
- 530
- ISSN
- 0004-6361
- DOI
- https://doi.org/10.1051/0004-6361/201016303
- Publikationsdatum
- 06-2011
- Peer-reviewed
- Ja
- ÖFOS 2012
- 103004 Astrophysik
- Schlagwörter
- Link zum Portal
- https://ucrisportal.univie.ac.at/de/publications/4ea867e1-e38b-4de6-a8a3-8a8550f5e9a8