Detection Of Solar-Like Oscillations, Observational Constraints, And Stellar Models For Θ Cyg, The Brightest Star Observed By The Kepler Mission

_ Cygni is an F3 spectral-type main-sequence star with visual magnitude V=4.48. This star was the brightest star observed by the original Kepler spacecraft mission. Short-cadence (58.8 s) photometric data using a custom aperture were obtained during Quarter 6 (June-September 2010) and subsequently in Quarters 8 and 12-17. We present analyses of the solar-like oscillations based on Q6 and Q8 data, identifying angular degree l = 0, 1, and 2 oscillations in the range 1000-2700 μHz, with a large frequency separation of 83.9 ± 0.4 μHz, and frequency with maximum amplitude _max = 1829 ± 54 μHz. We also present analyses of new ground-based spectroscopic observations, which, when combined with angular diameter measurements from interferometry and Hipparcos parallax, give Teff = 6697 ± 78 K, radius 1.49 ± 0.03 R⊙, [Fe/H] = -0.02 ± 0.06 dex, log g = 4.23 ± 0.03. We calculate stellar models matching the constraints using several methods, including using the Yale Rotating Evolution Code and the Asteroseismic Modeling Portal. The best-fit models have masses 1.35–1.39 M⊙ and ages 1.0–1.6 Gyr. _ Cyg’s Teff and log g place it cooler than the red edge of the Doradus instability region established from pre-Kepler ground-based observations, but just at the red edge derived from pulsation modeling. The best-fitting models have envelope convection-zone base temperature of ∼320,000 to 395,000 K. The pulsation models show Dor gravity-mode pulsations driven by the convectiveblocking mechanism, with periods of 0.3 to 1 day (frequencies 11 to 33 μHz). However, gravity modes were not detected in the Kepler data; one signal at 1.776 c d−1 (20.56 μHz) may be attributable to a faint, possibly background, binary. Asteroseismic studies of _ Cyg, in conjunction with those for other A-F stars observed by Kepler and CoRoT, will help to improve stellar model physics to sort out the confusing relationship between _ Sct and Dor pulsations and their hybrids, and to test pulsation driving mechanisms.