KIC 8410637: a 408-day period eclipsing binary containing a pulsating giant star

Context. Detached eclipsing binaries (dEBs) are ideal targets for accurately measuring of the masses and radii of their component stars. If at least one of the stars has evolved off the main sequence (MS), the masses and radii give a strict constraint on the age of the stars. Several dEBs containing a bright K giant and a fainter MS star have been discovered by the Kepler satellite. The mass and radius of a red giant (RG) star can also be derived from its asteroseismic signal. The parameters determined in this way depend on stellar models and may contain systematic errors. It is important to validate the asteroseismically determined mass and radius with independent methods. This can be done when stars are members of stellar clusters or members of dEBs. Aims. This paper presents an analysis of the dEB system KIC 8410637, which consists of an RG and an MS star. The aim is to derive accurate masses and radii for both components and provide the foundation for a strong test of the asteroseismic method and the accuracy of the deduced mass, radius, and age. Methods. We analysed high-resolution, high-signal-to-noise spectra from three different spectrographs. We also calculated a fit to the Kepler light curve and used ground-based photometry to determine the flux ratios between the component stars in the BVRI passbands. Results. We measured the masses and radii of the stars in the dEB, and the classical parameters Teff, log g ,and [Fe/H] from the spectra and ground-based photometry. The RG component of KIC 8410637 is most likely in the core helium-burning red clump phase of evolution and has an age and composition that are very similar to the stars in the open cluster NGC 6819. The mass of the RG in KIC 8410637 should therefore be similar to the mass of RGs in NGC 6819, thus lending support to the latest version of the asteroseismic scaling relations. This is the first direct me asurement of both mass and radius for an RG to be compared with values for RGs from asteroseismic scaling relations thereby providing an accurate comparison. We find excellent agreement bet ween log g values derived from the binary analysis and asteroseismic scaling relations. Conclusions. We have determined the masses and radii of the two stars in the binary accurately. A detailed asteroseismic analysis will be presented in a forthcoming paper, allowing an informative comparison between the parameters determined for the dEB and from asteroseismology.

[1]  John Southworth,et al.  Homogeneous studies of transiting extrasolar planets – IV. Thirty systems with space-based light curves , 2011, 1107.1235.

[2]  F. Grundahl,et al.  Asteroseismic inferences on red giants in open clusters NGC 6791, NGC 6819, and NGC 6811 using Kepler , 2011, 1104.4393.

[3]  T. R. Bedding,et al.  Eclipsing Binaries in the MACHO Database: New Periods and Classifications for 3031 Systems in the Large Magellanic Cloud , 2007, astro-ph/0703137.

[4]  Pieter Degroote,et al.  HERMES: a high-resolution fibre-fed spectrograph for the Mercator telescope , 2010, 1011.0258.

[5]  B. Smalley,et al.  Eclipsing binaries as standard candles: HD 23642 and the distance to the Pleiades , 2004, astro-ph/0409507.

[6]  L. Girardi,et al.  parsec: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code , 2012, 1208.4498.

[7]  A. Gimenez,et al.  Accurate masses and radii of normal stars: modern results and applications , 2009, 0908.2624.

[8]  H. Lehmann,et al.  Spectral analysis of Kepler SPB and β Cephei candidate stars , 2010, 1009.4316.

[9]  Paul B. Etzel,et al.  A Simple Synthesis Method for Solving the Elements of Well-Detached Eclipsing Systems , 1981 .

[10]  S. Zucker,et al.  Todcor: A TwO-Dimensional CORrelation technique to analyze stellar spectra in search of faint companions , 1994 .

[11]  Princeton,et al.  The Sloan Digital Sky Survey View of the Palomar-Green Bright Quasar Survey , 2005, astro-ph/0506022.

[12]  M. F. Andersen,et al.  Atmospheric parameters of 82 red giants in the Kepler field , 2012, 1205.5642.

[13]  P. Hadrava.  Relative line photometry of eclipsing binaries , 1997 .

[14]  Sara Seager,et al.  KEPLER ECLIPSING BINARY STARS. I. CATALOG AND PRINCIPAL CHARACTERIZATION OF 1879 ECLIPSING BINARIES IN THE FIRST DATA RELEASE , 2010, 1006.2815.

[15]  Michael R Chernick,et al.  Bootstrap Methods: A Guide for Practitioners and Researchers , 2007 .

[16]  William F. Welsh,et al.  KEPLER ECLIPSING BINARY STARS. II. 2165 ECLIPSING BINARIES IN THE SECOND DATA RELEASE , 2011, 1103.1659.

[17]  Paul G. Beck,et al.  Fast core rotation in red-giant stars as revealed by gravity-dominated mixed modes , 2011, Nature.

[18]  R. Claudi,et al.  Metal Abundances of Red Clump Stars in Open Clusters. I. NGC 6819 , 2000, astro-ph/0009321.

[19]  H. Winckel,et al.  DISCOVERY OF A RED GIANT WITH SOLAR-LIKE OSCILLATIONS IN AN ECLIPSING BINARY SYSTEM FROM KEPLER SPACE-BASED PHOTOMETRY , 2010, 1001.0399.

[20]  D. Stello,et al.  ASTEROSEISMIC CLASSIFICATION OF STELLAR POPULATIONS AMONG 13,000 RED GIANTS OBSERVED BY KEPLER , 2013, 1302.0858.

[21]  Conny Aerts,et al.  Gravity modes as a way to distinguish between hydrogen- and helium-burning red giant stars , 2011, Nature.

[22]  J. De Ridder,et al.  Characterization of red giant stars in the public Kepler data , 2011, 1103.0141.

[23]  P. Stetson.  DAOPHOT: A COMPUTER PROGRAM FOR CROWDED-FIELD STELLAR PHOTOMETRY , 1987 .

[24]  F. Grundahl,et al.  A LONG-PERIOD TOTALLY ECLIPSING BINARY STAR AT THE TURNOFF OF THE OPEN CLUSTER NGC 6819 DISCOVERED WITH KEPLER , 2012, 1211.2527.

[25]  F. Grundahl,et al.  Age and helium content of the open cluster NGC 6791 from multiple eclipsing binary members. I. Measurements, methods, and first results , 2010, 1009.5537.

[26]  Thomas Kallinger,et al.  SOUNDING OPEN CLUSTERS: ASTEROSEISMIC CONSTRAINTS FROM KEPLER ON THE PROPERTIES OF NGC 6791 AND NGC 6819 , 2011, 1102.2231.

[27]  L. Pasquini,et al.  Gravitational redshifts in main-sequence and giant stars , 2010, 1011.4635.

[28]  H. Hensberge,et al.  On the separation of component spectra in binary and higher-multiplicity stellar systems: bias progression and spurious patterns , 2008 .

[29]  D. Charbonneau,et al.  IDENTIFICATION, CLASSIFICATIONS, AND ABSOLUTE PROPERTIES OF 773 ECLIPSING BINARIES FOUND IN THE TRANS-ATLANTIC EXOPLANET SURVEY , 2007, 0712.0839.

[30]  S. M. Rucinski,et al.  Radial Velocity Studies of Close Binary Stars. VII. Methods and Uncertainties , 2002, astro-ph/0201214.

[31]  K. Kinemuchi,et al.  MODELING KEPLER OBSERVATIONS OF SOLAR-LIKE OSCILLATIONS IN THE RED GIANT STAR HD 186355 , 2011, 1109.0962.

[32]  P. Gaulme,et al.  RED GIANTS IN ECLIPSING BINARY AND MULTIPLE-STAR SYSTEMS: MODELING AND ASTEROSEISMIC ANALYSIS OF 70 CANDIDATES FROM KEPLER DATA , 2013, 1303.1197.

[33]  John Southworth,et al.  Homogeneous studies of transiting extrasolar planets – I. Light-curve analyses , 2008, 0802.3764.

[34]  John Southworth,et al.  Eclipsing binaries observed with the WIRE satellite. II. beta Aurigae and non-linear limb darkening , 2007 .

[35]  Tsevi Mazeh,et al.  STUDY OF SPECTROSCOPIC BINARIES WITH TODCOR. I: A NEW TWO-DIMENSIONAL CORRELATION ALGORITHM TO DERIVE THE RADIAL VELOCITIES OF THE TWO COMPONENTS , 1994 .

[36]  J. Hearnshaw,et al.  Precise Stellar Radial Velocities , 1998 .

[37]  M. Marconi,et al.  Ground-based follow-up in relation to Kepler asteroseismic investigation , 2010, 1003.6093.

[38]  Jonathan Devor.  SOLUTIONS FOR 10,000 ECLIPSING BINARIES IN THE BULGE FIELDS OF OGLE II USING DEBiL , 2005 .

[39]  David K. Sing,et al.  Stellar limb-darkening coefficients for CoRot and Kepler , 2009, 0912.2274.

[40]  A. Claret,et al.  Absolute dimensions of detached eclipsing binaries – I. The metallic‐lined system WW Aurigae , 2005, astro-ph/0507629.

[41]  William J. Chancellor,et al.  Soil Physical Properties , 1994 .

[42]  F. Grundahl,et al.  Age and helium content of the open cluster NGC 6791 from multiple eclipsing binary members , 2010, Astronomy & Astrophysics.

[43]  E. B. Carling,et al.  Photometric and Spectroscopic Binary Systems , 1981 .

[44]  Timothy M. Brown,et al.  KEPLER INPUT CATALOG: PHOTOMETRIC CALIBRATION AND STELLAR CLASSIFICATION , 2011, 1102.0342.

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

[46]  B. Scott Gaudi,et al.  Achieving Better Than 1 Minute Accuracy in the Heliocentric and Barycentric Julian Dates , 2010, 1005.4415.

[47]  Liverpool John Moores University,et al.  Population effects on the red giant clump absolute magnitude: The K-band , 2002, astro-ph/0208057.

[48]  E. H. Olsen,et al.  Absolute dimensions of eclipsing binaries. XXVIII. BK Pegasi and other F-type binaries: Prospects for calibration of convective core overshoot , 2010, 1004.1903.

[49]  B. Mosser,et al.  Asymptotic and measured large frequency separations , 2012, 1212.1687.

[50]  R. Hilditch,et al.  An Introduction to Close Binary Stars: Contents , 2001 .

[51]  L. Girardi,et al.  Theoretical isochrones in several photometric systems I. Johnson-Cousins-Glass, HST/WFPC2, HST/NICMOS, Washington, and ESO Imaging Survey filter sets , 2002, astro-ph/0205080.

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

[53]  J. Torra,et al.  A catalogue of eclipsing variables , 2006 .

[54]  P. Maxted,et al.  Eclipsing binaries in open clusters. II. V453 Cyg in NGC 6871 , 2004, astro-ph/0403572.

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

[56]  R. Hilditch.  An Introduction to Close Binary Stars , 2001 .

[57]  P. Quirion,et al.  Accurate fundamental parameters and detailed abundance patterns from spectroscopy of 93 solar-type Kepler targets , 2012 .