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We studied solar-like oscillations in 115 red giants in the three open clusters NGC 6791, NGC 6811, and NGC 6819, based on photometric data covering more than 19 months with NASAs Kepler space telescope. We present the asteroseismic diagrams of the asymptotic parameters delta u_02, delta u_01 and epsilon, which show clear correlation with fundamental stellar parameters such as mass and radius. When the stellar populations from the clusters are compared, we see evidence for a difference in mass of the red giant branch stars, and possibly a difference in structure of the red clump stars, from our measurements of the small separations delta u_02 and delta u_01. Ensemble {e}chelle diagrams and upper limits to the linewidths of l = 0 modes as a function of Delta u of the clusters NGC 6791 and NGC 6819 are also shown, together with the correlation between the l = 0 ridge width and the T_eff of the stars. Lastly, we distinguish between red giant branch and red clump stars through the measurement of the period spacing of mixed dipole modes in 53 stars among all the three clusters to verify the stellar classification from the color-magnitude diagram. These seismic results also allow us to identify a number of special cases, including evolved blue stragglers and binaries, as well as stars in late He-core burning phases, which can be potentially interesting targets for detailed theoretical modeling.
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 clus
We present initial results on some of the properties of open clusters NGC 6791 and NGC 6819 derived from asteroseismic data obtained by NASAs Kepler mission. In addition to estimating the mass, radius and log g of stars on the red-giant branch of the
We report on a UV-oriented imaging survey in the fields of the old, metal-rich open clusters, NGC 6791, NGC 6819 and NGC 7142. These three clusters represent both very near and ideal stellar aggregates to match the distinctive properties of the evolv
From $uvby-beta$ photometry of the open clusters NGC 6811 (75 stars), and NGC 6830 (19 stars) we were able to determine membership of the stars to each cluster, and fix the age and reddening for each. Since several short period stars have recently be
Asteroseismology of stars in clusters has been a long-sought goal because the assumption of a common age, distance and initial chemical composition allows strong tests of the theory of stellar evolution. We report results from the first 34 days of sc