DETECTION OF SOLAR-LIKE OSCILLATIONS, OBSERVATIONAL CONSTRAINTS, AND STELLAR MODELS FOR θ CYG, THE BRIGHTEST STAR OBSERVED BY THE KEPLER MISSION

• Published in: The Astrophysical journal 2016-11, Vol.831 (1), p.17
• Main Authors: Guzik, J. A., Houdek, G., Chaplin, W. J., Smalley, B., Kurtz, D. W., Gilliland, R. L., Mullally, F., Rowe, J. F., Bryson, S. T., Still, M. D., Antoci, V., Appourchaux, T., Basu, S., Bedding, T. R., Benomar, O., Garcia, R. A., Huber, D., Kjeldsen, H., Latham, D. W., Metcalfe, T. S., Pápics, P. I., White, T. R., Aerts, C., Ballot, J., Boyajian, T. S., Briquet, M., Bruntt, H., Buchhave, L. A., Campante, T. L., Catanzaro, G., Christensen-Dalsgaard, J., Davies, G. R., Doğan, G., Dragomir, D., Doyle, A. P., Elsworth, Y., Frasca, A., Gaulme, P., Gruberbauer, M., Handberg, R., Hekker, S., Karoff, C., Lehmann, H., Mathias, P., Mathur, S., Miglio, A., Molenda- akowicz, J., Mosser, B., Murphy, S. J., Régulo, C., Ripepi, V., Salabert, D., Sousa, S. G., Stello, D., Uytterhoeven, K.
• Format: Article
• Language: English
• Subjects: Apertures; asteroseismology; Astronomical models; ASTRONOMY AND ASTROPHYSICS; Astrophysics; Binary stars; Constraint modelling; Diameters; Gravitation; Ground-based observation; Main sequence stars; Model matching; Oscillations; Physics; Pulsation; Solar oscillations; Spacecraft; Stars & galaxies; stars: fundamental parameters; stars: interiors; stars: solar-type; Stellar evolution; Stellar models
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.3847/0004-637X/831/1/17

ABSTRACT θ Cygni is an F3 spectral type magnitude V = 4.48 main-sequence star that was the brightest star observed by the original Kepler spacecraft mission. Short-cadence (58.8 s) photometric data using a custom aperture were first obtained during Quarter 6 (2010 June-September) and subsequently in Quarters 8 and 12-17. We present analyses of solar-like oscillations based on Q6 and Q8 data, identifying angular degree l = 0, 1, and 2 modes with frequencies of 1000-2700 Hz, a large frequency separation of 83.9 0.4 Hz, and maximum oscillation amplitude at frequency max = 1829 54 Hz. We also present analyses of new ground-based spectroscopic observations, which, combined with interferometric angular diameter measurements, give Teff = 6697 78 K, radius 1.49 0.03 R , [Fe/H] = −0.02 0.06 dex, and log g = 4.23 0.03. We calculate stellar models matching these constraints using the Yale Rotating Evolution Code and the Asteroseismic Modeling Portal. The best-fit models have masses of 1.35-1.39 M and ages of 1.0-1.6 Gyr. θ Cyg's Teff and log g place it cooler than the red edge of the γ Doradus instability region established from pre-Kepler ground-based observations, but just at the red edge derived from pulsation modeling. The pulsation models show γ Dor gravity modes driven by the convective blocking mechanism, with frequencies of 1-3 cycles per day (11 to 33 Hz). However, gravity modes were not seen in Kepler data; one signal at 1.776 cycles per day (20.56 Hz) may be attributable to a faint, possibly background, binary.