Asteroseismic inferences on red giants in open clusters NGC 6791, NGC 6819, and NGC 6811 using Kepler

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

Research output: Contribution to journalArticle

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Abstract

Context. Four open clusters are present in the Kepler field of view and timeseries 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, NGC 6819 and NGC 6811. From these parameters and effective temperatures, we derive masses, radii and luminosities for the clusters as well as field red giants. Aims. We study the influence of evolution and metallicity on the observed red-giant populations. Methods. The global 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 the young cluster NGC 6811, the explanation of the position of the stars in the H-R diagram challenges the assumption of solar metallicity, and this open cluster might have significantly lower metallicity [Fe/H] in the range - 0.3 to - 0.7 dex. Also, nearly all the observed field stars seem to be older than NGC 6811 and younger than NGC 6791.

Original languageEnglish
Article numberA100
JournalAstronomy and Astrophysics
Volume530
DOIs
Publication statusPublished - 2011

Fingerprint

open clusters
inference
metallicity
diagram
oscillation
star distribution
diagrams
oscillations
field of view
damping
red giant stars
stars
temperature
star clusters
metal clusters
stellar mass
metal
luminosity
parameter
color

Keywords

  • Asteroseismology
  • Methods: observational
  • Open clusters and associations: general
  • Stars: late-type
  • Techniques: photometric

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Hekker, S., Basu, S., Stello, D., Kallinger, T., Grundahl, F., Mathur, S., ... Quintana, E. V. (2011). Asteroseismic inferences on red giants in open clusters NGC 6791, NGC 6819, and NGC 6811 using Kepler. Astronomy and Astrophysics, 530, [A100]. https://doi.org/10.1051/0004-6361/201016303

Asteroseismic inferences on red giants in open clusters NGC 6791, NGC 6819, and NGC 6811 using Kepler. / Hekker, S.; Basu, S.; Stello, D.; Kallinger, T.; Grundahl, F.; Mathur, S.; García, R. A.; Mosser, B.; Huber, D.; Bedding, T. R.; Szabó, R.; De Ridder, J.; Chaplin, W. J.; Elsworth, Y.; Hale, S. J.; Christensen-Dalsgaard, J.; Gilliland, R. L.; Still, M.; McCauliff, S.; Quintana, E. V.

In: Astronomy and Astrophysics, Vol. 530, A100, 2011.

Research output: Contribution to journalArticle

Hekker, S, Basu, S, Stello, D, Kallinger, T, Grundahl, F, Mathur, S, García, RA, Mosser, B, Huber, D, Bedding, TR, Szabó, R, De Ridder, J, Chaplin, WJ, Elsworth, Y, Hale, SJ, Christensen-Dalsgaard, J, Gilliland, RL, Still, M, McCauliff, S & Quintana, EV 2011, 'Asteroseismic inferences on red giants in open clusters NGC 6791, NGC 6819, and NGC 6811 using Kepler', Astronomy and Astrophysics, vol. 530, A100. https://doi.org/10.1051/0004-6361/201016303
Hekker, S. ; Basu, S. ; Stello, D. ; Kallinger, T. ; Grundahl, F. ; Mathur, S. ; García, R. A. ; Mosser, B. ; Huber, D. ; Bedding, T. R. ; Szabó, R. ; De Ridder, J. ; Chaplin, W. J. ; Elsworth, Y. ; Hale, S. J. ; Christensen-Dalsgaard, J. ; Gilliland, R. L. ; Still, M. ; McCauliff, S. ; Quintana, E. V. / Asteroseismic inferences on red giants in open clusters NGC 6791, NGC 6819, and NGC 6811 using Kepler. In: Astronomy and Astrophysics. 2011 ; Vol. 530.
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abstract = "Context. Four open clusters are present in the Kepler field of view and timeseries 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, NGC 6819 and NGC 6811. From these parameters and effective temperatures, we derive masses, radii and luminosities for the clusters as well as field red giants. Aims. We study the influence of evolution and metallicity on the observed red-giant populations. Methods. The global 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 the young cluster NGC 6811, the explanation of the position of the stars in the H-R diagram challenges the assumption of solar metallicity, and this open cluster might have significantly lower metallicity [Fe/H] in the range - 0.3 to - 0.7 dex. Also, nearly all the observed field stars seem to be older than NGC 6811 and younger than NGC 6791.",
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T1 - Asteroseismic inferences on red giants in open clusters NGC 6791, NGC 6819, and NGC 6811 using Kepler

AU - Hekker, S.

AU - Basu, S.

AU - Stello, D.

AU - Kallinger, T.

AU - Grundahl, F.

AU - Mathur, S.

AU - García, R. A.

AU - Mosser, B.

AU - Huber, D.

AU - Bedding, T. R.

AU - Szabó, R.

AU - De Ridder, J.

AU - Chaplin, W. J.

AU - Elsworth, Y.

AU - Hale, S. J.

AU - Christensen-Dalsgaard, J.

AU - Gilliland, R. L.

AU - Still, M.

AU - McCauliff, S.

AU - Quintana, E. V.

PY - 2011

Y1 - 2011

N2 - Context. Four open clusters are present in the Kepler field of view and timeseries 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, NGC 6819 and NGC 6811. From these parameters and effective temperatures, we derive masses, radii and luminosities for the clusters as well as field red giants. Aims. We study the influence of evolution and metallicity on the observed red-giant populations. Methods. The global 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 the young cluster NGC 6811, the explanation of the position of the stars in the H-R diagram challenges the assumption of solar metallicity, and this open cluster might have significantly lower metallicity [Fe/H] in the range - 0.3 to - 0.7 dex. Also, nearly all the observed field stars seem to be older than NGC 6811 and younger than NGC 6791.

AB - Context. Four open clusters are present in the Kepler field of view and timeseries 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, NGC 6819 and NGC 6811. From these parameters and effective temperatures, we derive masses, radii and luminosities for the clusters as well as field red giants. Aims. We study the influence of evolution and metallicity on the observed red-giant populations. Methods. The global 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 the young cluster NGC 6811, the explanation of the position of the stars in the H-R diagram challenges the assumption of solar metallicity, and this open cluster might have significantly lower metallicity [Fe/H] in the range - 0.3 to - 0.7 dex. Also, nearly all the observed field stars seem to be older than NGC 6811 and younger than NGC 6791.

KW - Asteroseismology

KW - Methods: observational

KW - Open clusters and associations: general

KW - Stars: late-type

KW - Techniques: photometric

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