Detection of Solar-like Oscillations, Observational Constraints, and Stellar Models for θ Cyg, the Brightest Star Observed By the Kepler Mission

Journal
Date Issued
2016
Author(s)
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.
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Huber, D.
•
Kjeldsen, H.
•
Latham, D. W.
•
Metcalfe, T. S.
•
Pápics, P. I.
•
White, T. R.
•
Aerts, C.
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Ballot, J.
•
Boyajian, T. S.
•
Briquet, M.
•
Bruntt, H.
•
Buchhave, L. A.
•
Campante, T. L.
•
•
Christensen-Dalsgaard, J.
•
Davies, G. R.
•
Doğan, G.
•
Dragomir, D.
•
Doyle, A. P.
•
Elsworth, Y.
•
•
Gaulme, P.
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Gruberbauer, M.
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Handberg, R.
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Hekker, S.
•
Karoff, C.
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Lehmann, H.
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Mathias, P.
•
Mathur, S.
•
Miglio, A.
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Molenda-Żakowicz, J.
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Mosser, B.
•
Murphy, S. J.
•
Régulo, C.
•
•
Salabert, D.
•
Sousa, S. G.
•
Stello, D.
•
Uytterhoeven, K.
DOI
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 μHz, a large frequency separation of 83.9 ± 0.4 μHz, and maximum oscillation amplitude at frequency ν max = 1829 ± 54 μHz. We also present analyses of new ground-based spectroscopic observations, which, combined with interferometric angular diameter measurements, give T eff = 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 T eff 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 μHz). However, gravity modes were not seen in Kepler data; one signal at 1.776 cycles per day (20.56 μHz) may be attributable to a faint, possibly background, binary.
Volume
831
Issue
1
Start page
17
Uri
Url
Issn Identifier
0004-637X
Ads BibCode
2016ApJ...831...17G
Rights
open.access
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