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arXiv · 1607.01035

Detection of Solar-Like Oscillations, Observational Constraints, and Stellar Models for $\theta$ Cyg, the Brightest Star Observed by the {\it Kepler} Mission

J. A. Guzik·G. Houdek·W. J. Chaplin·B. Smalley·D. W. Kurtz·R. L. Gilliland·F. Mullally·J. F. Rowe·S. T. Bryson·M. D. Still·V. Antoci·T. Appourchaux·S. Basu·T. R. Bedding·O. Benomar·R. A. Garcia·D. Huber·H. Kjeldsen·D. W. Latham·T. S. Metcalfe·P. I. Pápics·T. R. White·C. Aerts·J. Ballot·T. S. Boyajian·M. Briquet·H. Bruntt·L. A. Buchhave·T. L. Campante·G. Catanzaro·J. Christensen-Dalsgaard·G. R. Davies·G. Doğan·D. Dragomir·A. P. Doyle·Y. Elsworth·A. Frasca·P. Gaulme·M. Gruberbauer·R. Handberg·S. Hekker·C. Karoff·H. Lehmann·P. Mathias·S. Mathur·A. Miglio·J. Molenda-Żakowicz·B. Mosser·S. J. Murphy·C. Régulo·V. Ripepi·D. Salabert·S. G. Sousa·D. Stello·K. Uytterhoeven
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Abstract

$\theta$ 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.

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J. A. Guzik, G. Houdek, W. J. Chaplin, B. Smalley, D. W. Kurtz, R. L. Gilliland, F. Mullally, J. F. Rowe, S. T. Bryson, M. D. Still, V. Antoci, T. Appourchaux, S. Basu, T. R. Bedding, O. Benomar, R. A. Garcia, D. Huber, H. Kjeldsen, D. W. Latham, T. S. Metcalfe, P. I. Pápics, T. R. White, C. Aerts, J. Ballot, T. S. Boyajian, M. Briquet, H. Bruntt, L. A. Buchhave, T. L. Campante, G. Catanzaro, J. Christensen-Dalsgaard, G. R. Davies, G. Doğan, D. Dragomir, A. P. Doyle, Y. Elsworth, A. Frasca, P. Gaulme, M. Gruberbauer, R. Handberg, S. Hekker, C. Karoff, H. Lehmann, P. Mathias, S. Mathur, A. Miglio, J. Molenda-Żakowicz, B. Mosser, S. J. Murphy, C. Régulo, V. Ripepi, D. Salabert, S. G. Sousa, D. Stello, K. Uytterhoeven. 2016-07-04. Detection of Solar-Like Oscillations, Observational Constraints, and Stellar Models for $\theta$ Cyg, the Brightest Star Observed by the {\it Kepler} Mission. https://doi.org/10.3847/0004-637x/831/1/17

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