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Frank Grundahl

Asteroseismology of old open clusters with Kepler: direct estimate of the integrated red giant branch mass-loss in NGC 6791 and 6819

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  • A. Miglio, School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT
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  • Karsten Frank Brogaard
  • D. Stello, Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW 2006, Australia
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  • W. J. Chaplin, School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT
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  • F. D'Antona, INAF - Osservatorio Astronomico di Roma, via Frascati 33, Monteporzio Catone (RM), Italy
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  • J. Montalbán, Institut d'Astrophysique et de Géophysique de l'Université de Liège, Allée du 6 Août, 17 B-4000 Liège, Belgium
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  • S. Basu, Department of Astronomy, Yale University, PO Box 208101, New Haven, CT 06520-8101, USA
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  • A. Bressan, SISSA, via Bonomea 265, 34136 Trieste, Italy
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  • F. Grundahl
  • M. Pinsonneault, Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA
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  • A. M. Serenelli, Institute for Space Sciences (CSIC-IEEC), Facultad de Ciencies, Campus UAB, 08193 Bellaterra, Spain
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  • Y. Elsworth, School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT
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  • S. Hekker, School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT
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  • T. Kallinger, Department of Physics and Astronomy, University of British Colombia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada
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  • B. Mosser, LESIA, CNRS, Université Pierre et Marie Curie, Université Denis Diderot, Observatoire de Paris, 92195 Meudon Cedex, France
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  • P. Ventura, INAF - Osservatorio Astronomico di Roma, via Frascati 33, Monteporzio Catone (RM), Italy
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  • A. Bonanno, INAF - Osservatorio Astrofisico di Catania, Via S.Sofia 78, 95123 Catania, Italy
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  • A. Noels, Institut d'Astrophysique et de Géophysique de l'Université de Liège, Allée du 6 Août, 17 B-4000 Liège, Belgium
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  • Victor Silva Aguirre
  • R. Szabo, Konkoly Observatory of the Hungarian Academy of Sciences, Konkoly Thege Miklós út 15-17, H-1121 Budapest, Hungary
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  • J. Li, SETI Institute/NASA Ames Research Center, Moffett Field, CA 94035, USA
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  • S. McCauliff, Orbital Sciences Corporation/NASA Ames Research Center, Moffett Field, CA 94035, USA
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  • C. K. Middour, Orbital Sciences Corporation/NASA Ames Research Center, Moffett Field, CA 94035, USA
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  • H. Kjeldsen
Mass-loss of red giant branch (RGB) stars is still poorly determined, despite its crucial role in the chemical enrichment of galaxies. Thanks to the recent detection of solar-like oscillations in G-K giants in open clusters with Kepler, we can now directly determine stellar masses for a statistically significant sample of stars in the old open clusters NGC 6791 and 6819. The aim of this work is to constrain the integrated RGB mass-loss by comparing the average mass of stars in the red clump (RC) with that of stars in the low-luminosity portion of the RGB [i.e. stars with L≲L(RC)]. Stellar masses were determined by combining the available seismic parameters νmax and Δν with additional photometric constraints and with independent distance estimates. We measured the masses of 40 stars on the RGB and 19 in the RC of the old metal-rich cluster NGC 6791. We find that the difference between the average mass of RGB and RC stars is small, but significant [? (random) ±0.04 (systematic) M&sun;]. Interestingly, such a small ? does not support scenarios of an extreme mass-loss for this metal-rich cluster. If we describe the mass-loss rate with Reimers prescription, a first comparison with isochrones suggests that the observed ? is compatible with a mass-loss efficiency parameter in the range 0.1 ≲η≲ 0.3. Less stringent constraints on the RGB mass-loss rate are set by the analysis of the ˜2 Gyr old NGC 6819, largely due to the lower mass-loss expected for this cluster, and to the lack of an independent and accurate distance determination. In the near future, additional constraints from frequencies of individual pulsation modes and spectroscopic effective temperatures will allow further stringent tests of the Δν and νmax scaling relations, which provide a novel, and potentially very accurate, means of determining stellar radii and masses.
Original languageEnglish
JournalRoyal Astronomical Society. Monthly Notices
Volume419
Issue3
Pages (from-to)2077-2088
Number of pages12
ISSN0035-8711
DOIs
Publication statusPublished - 1 Jan 2012

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