DETECTION OF SOLAR-LIKE OSCILLATIONS, OBSERVATIONAL CONSTRAINTS, AND STELLAR MODELS FOR theta CYG, THE BRIGHTEST STAR OBSERVED BY THE 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, Hans Kjeldsen, D. W. Latham, T. S. MetcalfeP. I. Papics, 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. Dogan, 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-Zakowicz, B. Mosser, S. J. Murphy, C. Regulo, V. Ripepi, D. Salabert, S. G. Sousa, D. Stello, K. Uytterhoeven

*Corresponding author for this work

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

Abstract

theta 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 mu Hz, a large frequency separation of 83.9 +/- 0.4 mu Hz, and maximum oscillation amplitude at frequency nu(max) = 1829 +/- 54 mu Hz. 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 Re-circle dot, [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-circle dot and ages of 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 modes driven by the convective blocking mechanism, with frequencies of 1-3 cycles per day (11 to 33 mu Hz). However, gravity modes were not seen in Kepler data; one signal at 1.776 cycles per day (20.56 mu Hz) may be attributable to a faint, possibly background, binary.

Original languageEnglish
Article number17
JournalThe Astrophysical Journal
Volume831
Issue1
Number of pages22
ISSN0004-637X
DOIs
Publication statusPublished - 1 Nov 2016

Keywords

  • asteroseismology
  • stars: fundamental parameters
  • stars: interiors
  • stars: solar-type
  • MAIN-SEQUENCE STARS
  • GAMMA DORADUS STARS
  • F-TYPE STARS
  • EXOPLANET HOST STARS
  • INFRARED FLUX METHOD
  • EFFECTIVE TEMPERATURES
  • NEARBY STARS
  • DELTA SCT
  • A-TYPE
  • SPECTROSCOPIC PARAMETERS

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