The age and distance of the Kepler open cluster NGC 6811 from an eclipsing binary, turnoff star pulsation, and giant asteroseismology
- San Diego State University, Department of Astronomy, San Diego, CA, 92182 (United States)
- Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark)
- University of Texas, McDonald Observatory, HC75 Box 1337-L Fort Davis, TX, 79734 (United States)
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
- Humboldt State University, Department of Physics and Astronomy, 1 Harpst St., Arcata, CA, 95521 (United States)
- Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW, 2006 (Australia)
- Department of Physics and Astronomy, University of Victoria, P.O. Box 3055, Victoria, BC V8W 3P6 (Canada)
We present the analysis of an eccentric, partially eclipsing long-period (P = 19.23 days) binary system KIC 9777062 that contains main-sequence stars near the turnoff of the intermediate-age open cluster NGC 6811. The primary is a metal-lined Am star with a possible convective blueshift to its radial velocities, and one star (probably the secondary) is likely to be a γ Dor pulsator. The component masses are 1.603 ± 0.006(stat.) ± 0.016(sys.) and 1.419 ± 0.003 ± 0.008 M{sub ⊙}, and the radii are 1.744 ± 0.004 ± 0.002 and 1.544 ± 0.002 ± 0.002 R{sub ⊙}. The isochrone ages of the stars are mildly inconsistent: the age from the mass–radius combination for the primary (1.05 ± 0.05 ± 0.09 Gyr, where the last quote was systematic uncertainty from models and metallicity) is smaller than that from the secondary (1.21 ± 0.05 ± 0.15 Gyr) and is consistent with the inference from the color–magnitude diagram (1.00 ± 0.05 Gyr). We have improved the measurements of the asteroseismic parameters Δν and ν {sub max} for helium-burning stars in the cluster. The masses of the stars appear to be larger (or alternately, the radii appear to be smaller) than predicted from isochrones using the ages derived from the eclipsing stars. The majority of stars near the cluster turnoff are pulsating stars: we identify a sample of 28 δ Sct, 15 γ Dor, and 5 hybrid types. We used the period–luminosity relation for high-amplitude δ Sct stars to fit the ensemble of the strongest frequencies for the cluster members, finding (m−M){sub V}=10.37±0.03. This is larger than most previous determinations, but smaller than values derived from the eclipsing binary (10.47 ± 0.05).
- OSTI ID:
- 22868554
- Journal Information:
- Astrophysical Journal, Vol. 831, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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