Interferometric radii of bright Kepler stars with the CHARA Array: θ Cygni and 16 Cygni A and B

We present the results of long-baseline optical interferom etry observations using the Precision Astronomical Visual Observations (PAVO) beam combiner at the Center for High Angular Resolution Astronomy (CHARA) Array to measure the angular sizes of three bright Kepler stars: θ Cygni, and both components of the binary system 16 Cygni. Supporting infrared observations were made with the Michigan Infrared Combiner (MIRC) and Classic beam combiner, also at the CHARA Array. We find limb-darkened angular diameters of 0.753 ± 0.009 mas for θ Cyg, 0.539 ± 0.007 mas for 16 Cyg A and 0.490 ± 0.006 mas for 16 Cyg B. The Kepler Mission has observed these stars with outstanding photometric precision, revealing the presence of solar-like oscillations. Due to the brightness of these stars the oscillations have exceptiona l signal-to-noise, allowing for detailed study through asteroseismology, and are well constrained by other observations. We have combined our interferometric diameters with Hipparcos parallaxes, spectrophotometric bolometric fluxes and the asteroseismic large frequency sep aration to measure linear radii (θ Cyg: 1.48±0.02 R⊙, 16 Cyg A: 1.22±0.02 R⊙, 16 Cyg B: 1.12±0.02 R⊙), effective temperatures (θ Cyg: 6749±44 K, 16 Cyg A: 5839±42 K, 16 Cyg B: 5809±39 K), and masses (θ Cyg: 1.37±0.04 M⊙, 16 Cyg A: 1.07±0.05 M⊙, 16 Cyg B: 1.05±0.04 M⊙) for each star with very little model dependence. The measurements presented here will provide strong constraints for future stellar modelling efforts.

[1]  L. Casagrande,et al.  New constraints on the chemical evolution of the solar neighbourhood and galactic disc(s) - improved astrophysical parameters for the Geneva-Copenhagen Survey , 2011, 1103.4651.

[2]  Thomas G. Barnes,et al.  Stellar angular diameters and visual surface brightness – III. An improved definition of the relationship , 1978 .

[3]  Harold A. McAlister,et al.  Search for Faint Companions to Nearby Solar-like Stars using the Adaptive Optics System at Mount Wilson Observatory , 2001 .

[4]  ASTEROSEISMOLOGY OF THE OPEN CLUSTERS NGC 6791, NGC 6811, AND NGC 6819 FROM 19 MONTHS OF KEPLER PHOTOMETRY , 2012, 1205.4023.

[5]  M. Deleuil,et al.  Oscillating red giants in the CoRoT exofield: asteroseismic mass and radius determination , 2008, 0811.4674.

[6]  Paolo Conconi,et al.  Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series , 2012 .

[7]  S. Ridgway,et al.  CHARA Array Measurements of the Angular Diameters of Exoplanet Host Stars , 2008, 0803.1411.

[8]  P. Gaulme,et al.  CONSTRUCTING A ONE-SOLAR-MASS EVOLUTIONARY SEQUENCE USING ASTEROSEISMIC DATA FROM KEPLER , 2011, 1108.2031.

[9]  M. J. Creech-Eakman,et al.  The Palomar Testbed Interferometer Calibrator Catalog , 2007, 0711.4194.

[10]  W. J. Tango,et al.  The radius and mass of the subgiant star β Hyi from interferometry and asteroseismology , 2007 .

[11]  B. Smalley,et al.  Accurate fundamental parameters for 23 bright solar-type stars , 2010, 1002.4268.

[12]  Frantz Martinache,et al.  Mapping the Shores of the Brown Dwarf Desert. I. Upper Scorpius , 2008 .

[13]  C. Aerts,et al.  CoRoT Measures Solar-Like Oscillations and Granulation in Stars Hotter Than the Sun , 2008, Science.

[14]  P. Hauschildt,et al.  Surface convection and red-giant radius measurements , 2010, 1010.3649.

[15]  P. Quirion,et al.  Automated extraction of oscillation parameters for Kepler observations of solar-type stars , 2009, 0910.2764.

[16]  R. Drimmel,et al.  A three-dimensional Galactic extinction model , 2003, astro-ph/0307273.

[17]  F. V. Leeuwen.  Validation of the new Hipparcos reduction , 2007, 0708.1752.

[18]  H. M. Antia,et al.  Oscillation mode linewidths of main-sequence and subgiant stars observed by Kepler , 2011, 1112.3295.

[19]  Howard Isaacson,et al.  FUNDAMENTAL PROPERTIES OF KEPLER PLANET-CANDIDATE HOST STARS USING ASTEROSEISMOLOGY , 2013, 1302.2624.

[20]  Michael S. Bessell,et al.  Spectrophotometric Libraries, Revised Photonic Passbands, and Zero Points for UBVRI, Hipparcos, and Tycho Photometry , 2011, 1112.2698.

[21]  H A McAlister,et al.  HD 181068: A Red Giant in a Triply Eclipsing Compact Hierarchical Triple System , 2011, Science.

[22]  M. Asplund,et al.  Accurate abundance patterns of solar twins and analogs - Does the anomalous solar chemical composition come from planet formation? , 2009, 0911.1893.

[23]  P. Morel,et al.  Fundamental properties of the Population II fiducial stars HD 122563 and Gmb 1830 from CHARA interferometric observations , 2012, 1207.5954.

[24]  R. H. Brown,et al.  The effects of limb darkening on measurements of angular size with an intensity interferometer , 1974 .

[25]  Arthur D. Code,et al.  Empirical effective temperatures and bolometric corrections for early-type stars , 1976 .

[26]  JØrgen Christensen-Dalsgaard.  Physics of solar-like oscillations , 2004 .

[27]  William J. Chaplin,et al.  DETERMINATION OF STELLAR RADII FROM ASTEROSEISMIC DATA , 2009, 0909.0506.

[28]  Michael S. Bessell,et al.  The Hipparcos and Tycho Photometric System Passbands , 2000 .

[29]  W. Chaplin,et al.  Mode lifetimes of stellar oscillations - Implications for asteroseismology , 2009, 0905.1722.

[30]  L. Bigot,et al.  The limb darkening of $\mathsf{\alpha}$ Centauri B - Matching 3D hydrodynamical models with interferometric measurements , 2006 .

[31]  M. R. Haas,et al.  Kepler Mission Design, Realized Photometric Performance, and Early Science , 2010, 1001.0268.

[32]  B. Krauskopf,et al.  Proc of SPIE , 2003 .

[33]  J. M. Matthews,et al.  Asteroseismology of red giants from the first four months of Kepler data: Fundamental stellar parameters , 2010, 1010.4589.

[34]  M. Asplund,et al.  Three-dimensional hydrodynamical simulations of red giant stars: semi-global models for interpreting interferometric observations , 2010, 1009.1745.

[35]  R. Paul Butler,et al.  A Multisite Campaign to Measure Solar-like Oscillations in Procyon. I. Observations, Data Reduction, and Slow Variations , 2008, 0807.3794.

[36]  J. Mathis,et al.  The relationship between infrared, optical, and ultraviolet extinction , 1989 .

[37]  D. Mourard,et al.  A new interferometric study of four exoplanet host stars: θ Cygni, 14 Andromedae, υ Andromedae and 42 Draconis , 2012, 1208.3895.

[38]  Russel J. White,et al.  STELLAR DIAMETERS AND TEMPERATURES. II. MAIN-SEQUENCE K- AND M-STARS , 2012, 1208.2431.

[39]  The Geneva-Copenhagen survey of the Solar neighbourhood II. New uvby calibrations and rediscussion of stellar ages, the G dwarf problem, age-metallicity diagram, and heating mechanisms of the disk , 2007, 0707.1891.

[40]  P. Demarque,et al.  The case of Alpha Centauri - Mass, age and p-mode oscillation spectrum , 1986 .

[41]  M. A. C. Perryman,et al.  The Hipparcos and Tycho catalogues : astrometric and photometric star catalogues derived from the ESA Hipparcos Space Astrometry Mission , 1997 .

[42]  S. D. Kawaler,et al.  Ensemble Asteroseismology of Solar-Type Stars with the NASA Kepler Mission , 2011, Science.

[43]  G. Handler,et al.  Kepler Asteroseismology Program: Introduction and First Results , 2009, 1001.0139.

[44]  F. Thevenin,et al.  The angular sizes of dwarf stars and subgiants Surface brightness relations calibrated by interferometry , 2004, astro-ph/0404180.

[45]  Jie Li,et al.  Kepler-22b: A 2.4 EARTH-RADIUS PLANET IN THE HABITABLE ZONE OF A SUN-LIKE STAR , 2011, The Astrophysical Journal.

[46]  P. Gaulme,et al.  Global asteroseismic properties of solar-like oscillations observed by Kepler: a comparison of complementary analysis methods , 2011, 1105.0571.

[47]  SF2A-2012: Proceedings of the Annual meeting of the French Society of Astronomy and Astrophysics. Eds.: S. Boissier, P. de Laverny, N. Nardetto, R. Samadi, D. Valls-Gabaud and H. Wozniak, pp.677-680 , 2012 .

[48]  S. D. Kawaler,et al.  University of Birmingham Asteroseismology of the solar analogs 16 Cyg A and B from Kepler observations , 2012 .

[49]  M. Langlois,et al.  Society of Photo-Optical Instrumentation Engineers , 2005 .

[50]  J. De Ridder,et al.  Solar-like oscillations in red giants observed with Kepler: comparison of global oscillation parameters from different methods , 2010, 1008.2959.

[51]  Gerard Zins,et al.  SearchCal: a Virtual Observatory tool for searching calibrators in optical long-baseline interferometry II. The faint-object case , 2006 .

[52]  G. Zins,et al.  SearchCal: a Virtual Observatory tool for searching calibrators in optical long-baseline interferometry II. The faint-object case , 2006, astro-ph/0607026.

[53]  J. Sturmann,et al.  The radius and mass of the close solar twin 18 Scorpii derived from asteroseismology and interferometry , 2011, 1209.0217.

[54]  T. Appourchaux,et al.  RADIUS DETERMINATION OF SOLAR-TYPE STARS USING ASTEROSEISMOLOGY: WHAT TO EXPECT FROM THE KEPLER MISSION , 2009, 0906.0766.

[55]  Ellyn K. Baines,et al.  ELEVEN EXOPLANET HOST STAR ANGULAR DIAMETERS FROM THE CHARA ARRAY , 2009, 0906.2702.

[56]  Hans Kjeldsen,et al.  CALCULATING ASTEROSEISMIC DIAGRAMS FOR SOLAR-LIKE OSCILLATIONS , 2011, 1109.3455.

[57]  W. D. Cochran,et al.  The Discovery of a Planetary Companion to 16 Cygni B , 1997 .

[58]  S. S. Olivier,et al.  Stellar Companions to Stars with Planets , 2002, astro-ph/0207538.

[59]  A. Matter,et al.  Three-dimensional interferometric, spectrometric, and planetary views of Procyon , 2012, 1201.3264.

[60]  S. Bloemen,et al.  Gravity and limb-darkening coefficients for the Kepler, CoRoT, Spitzer, uvby, UBVRIJHK, and Sloan photometric systems , 2011 .

[61]  Brian D. Mason,et al.  The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog , 2001 .

[62]  R. K. Ulrich,et al.  Determination of stellar ages from asteroseismology , 1986 .

[63]  S. Deheuvels,et al.  Constraints on the structure of the core of subgiants via mixed modes: the case of HD 49385 , 2011, 1109.1191.

[64]  J. De Ridder,et al.  FUNDAMENTAL PROPERTIES OF STARS USING ASTEROSEISMOLOGY FROM KEPLER AND CoRoT AND INTERFEROMETRY FROM THE CHARA ARRAY , 2012, 1210.0012.

[65]  S. Ridgway,et al.  ANGULAR DIAMETERS OF THE HYADES GIANTS MEASURED WITH THE CHARA ARRAY , 2008, 0810.2238.

[66]  J. Ridder,et al.  Amplitudes and lifetimes of solar-like oscillations observed by CoRoT* Red-giant versus main-sequence stars , 2011, 1102.1896.

[67]  G. Marcy,et al.  The Orbit of 16 Cygni AB , 1999 .

[68]  C. Moutou,et al.  Extrasolar planets and brown dwarfs around A-F type stars - VII. Theta Cygni radial velocity variations: planets or stellar phenomenon? , 2009, 0908.4521.

[69]  P. North,et al.  Automated spectroscopic abundances of A and F-type stars using echelle spectrographs - II. Abundances of 140 A-F stars from ELODIE and CORALIE , 2002, astro-ph/0210065.

[70]  M. Skrutskie,et al.  The Two Micron All Sky Survey (2MASS) , 2006 .

[71]  William J. Chaplin,et al.  AN IN-DEPTH STUDY OF GRID-BASED ASTEROSEISMIC ANALYSIS , 2010, 1009.3018.

[72]  Timothy M. Brown,et al.  Detection of possible p-mode oscillations on Procyon , 1991 .

[73]  J. E. O'Donnell.  R(sub nu)-dependent optical and near-ultraviolet extinction , 1994 .

[74]  R. Stein,et al.  THE MASS MIXING LENGTH IN CONVECTIVE STELLAR ENVELOPES , 2011, 1102.1102.

[75]  S. T. Ridgway,et al.  First Results from the CHARA Array. II. A Description of the Instrument , 2005 .

[76]  William C. Danchi,et al.  Advances in Stellar Interferometry , 2006 .

[77]  Laszlo Sturmann,et al.  STELLAR DIAMETERS AND TEMPERATURES. I. MAIN-SEQUENCE A, F, AND G STARS , 2011, 1112.3316.