Detection of Solar-Like Oscillations, Observational Constraints, and Stellar Models for $θ$ Cyg, the Brightest Star Observed by the {\it Kepler} Mission
Creators: name: Guzik, J. A.
name: Houdek, G.
name: Chaplin, W. J.
name: Smalley, B.
name: Kurtz, D. W.
name: Gilliland, R. L.
name: Mullally, F.
name: Rowe, J. F.
name: Bryson, S. T.
name: Still, M. D.
name: Antoci, V.
name: Appourchaux, T.
name: Basu, S.
name: Bedding, T. R.
name: Benomar, O.
name: Garcia, R. A.
name: Huber, D.
name: Kjeldsen, H.
name: Latham, D. W.
name: Metcalfe, T. S.
name: Pápics, P. I.
name: White, T. R.
name: Aerts, C.
name: Ballot, J.
name: Boyajian, T. S.
name: Briquet, M.
name: Bruntt, H.
name: Buchhave, L. A.
name: Campante, T. L.
name: Catanzaro, G.
name: Christensen-Dalsgaard, J.
name: Davies, G. R.
name: Doğan, G.
name: Dragomir, D.
name: Doyle, A. P.
name: Elsworth, Y.
name: Frasca, A.
name: Gaulme, P.
name: Gruberbauer, M.
name: Handberg, R.
name: Hekker, S.
name: Karoff, C.
name: Lehmann, H.
name: Mathias, P.
name: Mathur, S.
name: Miglio, A.
name: Molenda-Żakowicz, J.
name: Mosser, B.
name: Murphy, S. J.
name: Régulo, C.
name: Ripepi, V.
name: Salabert, D.
name: Sousa, S. G.
name: Stello, D.
name: Uytterhoeven, K.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: $θ$ 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 microHz, with a large frequency separation of 83.9 plus/minus 0.4 microHz, and frequency with maximum amplitude 1829 plus/minus 54 microHz. We also present analyses of new ground-based spectroscopic observations, which, when combined with angular diameter measurements from interferometry and Hipparcos parallax, give T_eff = 6697 plus/minus 78 K, radius 1.49 plus/minus 0.03 solar radii, [Fe/H] = -0.02 plus/minus 0.06 dex, and log g = 4.23 plus/minus 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 solar masses and ages 1.0-1.6 Gyr. theta Cyg's T_eff and log g place it cooler than the red edge of the gamma Doradus instability region established from pre-Kepler ground-based observations, but just at the red edge derived from pulsation modeling. The pulsation models show gamma Dor gravity-mode pulsations driven by the convective-blocking mechanism, with frequencies of 1 to 3 cycles/day (11 to 33 microHz). However, gravity modes were not detected in the Kepler data, one signal at 1.776 cycles/day (20.56 microHz) may be attributable to a faint, possibly background, binary. Asteroseismic studies of theta Cyg and other A-F stars observed by Kepler and CoRoT, will help to improve stellar model physics and to test pulsation driving mechanisms.
description: Accepted for Publication in The Astrophysical Journal, July 1, 2016