TrES-4: A Transiting Hot Jupiter of Very Low Density

We report the discovery of TrES-4, a hot Jupiter that transits the star GSC 02620-00648 every 3.55 days. From high-resolution spectroscopy of the star, we estimate a stellar effective temperature of K, and T p 6100 150 eff from high-precision z and B photometry of the transit we constrain the ratio of the semimajor axis a and the stellar radius to be . We compare these values to model stellar isochrones to constrain the stellar Ra /R p 6.03 0.13 ∗∗ mass to be . Based on this estimate and the photometric time series, we constrain the stellar M p 1.22 0.17 M ∗ , radius to be and the planet radius to be . We model our radial R p 1.738 0.092 RR p 1.674 0.094 R ∗ , p Jup velocity data assuming a circular orbit and find a planetary mass of . Our radial velocity observations 0.84 0.10 MJup rule out line-bisector variations that would indicate a specious detection resulting from a blend of an eclipsing binary system. TrES-4 has the largest radius and lowest density of any of the known transiting planets. It presents a challenge to current models of the physical structure of hot Jupiters and indicates that the diversity of physical properties among the members of this class of exoplanets has yet to be fully explored. Subject headings: planetary systems — techniques: photometric — techniques: radial velocities — techniques: spectroscopic

[1]  A. Claret,et al.  A new non-linear limb-darkening law for LTE stellar atmosphere models III - Sloan filters: Calculations for –5.0 ≤ log [M/H] ≤ +1, 2000 K ≤ T$\mathsf{_{eff}}$ ≤ 50 000 K at several surface gravities , 2004 .

[2]  M. Mayor,et al.  An extended upper atmosphere around the extrasolar planet HD209458b , 2003, Nature.

[3]  Arlo U. Landolt,et al.  UBVRI Photometric Standard Stars in the Magnitude Range 11 , 1992 .

[4]  Canada.,et al.  Atmospheric escape from hot Jupiters , 2004, astro-ph/0403369.

[5]  M. Holman,et al.  The Transit Light Curve Project. III. Tres Transits of TrES-1 , 2006, astro-ph/0611404.

[6]  David Charbonneau,et al.  The Challenge of Wide-Field Transit Surveys: The Case of GSC 01944-02289 , 2005, astro-ph/0501554.

[7]  I. Hubeny,et al.  Possible Solutions to the Radius Anomalies of Transiting Giant Planets , 2006 .

[8]  David Charbonneau,et al.  TrES-3: A Nearby, Massive, Transiting Hot Jupiter in a 31 Hour Orbit , 2007, 0705.2004.

[9]  Mark S. Marley,et al.  Planetary Radii across Five Orders of Magnitude in Mass and Stellar Insolation: Application to Transits , 2006 .

[10]  To Appear in ApJ Preprint typeset using L ATEX style emulateapj v. 6/22/04 THE EFFECTIVE TEMPERATURE SCALE OF FGK STARS. II. Teff: COLOR: [Fe/H] CALIBRATIONS , 2008 .

[11]  A KECK HIRES DOPPLER SEARCH FOR PLANETS ORBITING METAL-POOR DWARFS. I. TESTING GIANT PLANET FORMATION AND MIGRATION SCENARIOS , 2006, astro-ph/0605670.

[12]  G. Laughlin,et al.  On the Radii of Extrasolar Giant Planets , 2003 .

[13]  Y.-W. Lee,et al.  Toward Better Age Estimates for Stellar Populations: The Y2 Isochrones for Solar Mixture , 2001 .

[14]  C. Flynn,et al.  Accurate fundamental parameters for lower main‐sequence stars , 2006, astro-ph/0608504.

[15]  David Charbonneau,et al.  TrES-1: The Transiting Planet of a Bright K0 V Star , 2004 .

[16]  David Charbonneau,et al.  PRECISE RADIUS ESTIMATES FOR THE EXOPLANETS WASP-1b AND WASP-2b , 2007 .

[17]  Carnegie,et al.  HAT-P-1b: A Large-Radius, Low-Density Exoplanet Transiting One Member of a Stellar Binary* ** , 2007 .

[18]  Edward W. Dunham,et al.  PSST: The Planet Search Survey Telescope , 2004 .

[19]  Massachusetts Institute of Technology,et al.  Improving Stellar and Planetary Parameters of Transiting Planet Systems: The Case of TrES-2 , 2007, 0704.2938.

[20]  Saurabh Jha,et al.  An extrasolar planet that transits the disk of its parent star , 2003, Nature.

[21]  David Charbonneau,et al.  TrES-2: The First Transiting Planet in the Kepler Field , 2006, astro-ph/0609335.

[22]  M. Couture,et al.  HIRES: the high-resolution echelle spectrometer on the Keck 10-m Telescope , 1994, Astronomical Telescopes and Instrumentation.

[23]  E. Agol,et al.  Analytic Light Curves for Planetary Transit Searches , 2002, astro-ph/0210099.

[24]  William H. Press,et al.  Numerical recipes in C , 2002 .

[25]  P. H. Hauschildt,et al.  Evolutionary models for cool brown dwarfs and extrasolar giant planets. The case of HD 209458 , 2003 .

[26]  Spectroscopic Binaries in a Sample of ROSAT X-Ray Sources South of the Taurus Molecular Clouds* , 2001, astro-ph/0112294.

[27]  David Charbonneau,et al.  The transit light curve project. I. Four consecutive transits of the exoplanet XO-1b , 2006 .

[28]  Berkeley,et al.  Testing Blend Scenarios for Extrasolar Transiting Planet Candidates. II. OGLE-TR-56 , 2005 .

[29]  William B. Hubbard,et al.  A Theory for the Radius of the Transiting Giant Planet HD 209458b , 2003, astro-ph/0305277.

[30]  R. Rosenfeld.  Nature , 2009, Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery.

[31]  David Charbonneau,et al.  Using Stellar Limb-Darkening to Refine the Properties of HD 209458b , 2006, astro-ph/0603542.

[32]  M. Holman,et al.  The Transit Light Curve (TLC) Project. VI. Three Transits of the Exoplanet TrES-2 , 2007, 0704.2907.

[33]  European Southern Observatory,et al.  The CORALIE survey for southern extra-solar planets - IX. A 1.3-day period brown dwarf disguised as a planet , 2002 .

[34]  “Hot Jupiters” , 2006 .

[35]  Bruce W. Carney,et al.  A Survey of Proper-Motion Stars. XVI. Orbital Solutions for 171 Single-lined Spectroscopic Binaries , 2002 .

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

[37]  Gilles Chabrier,et al.  Heat transport in giant (exo)planets: a new perspective , 2007 .

[38]  Tristan Guillot,et al.  Astronomy and Astrophysics Evolution of " 51 Peg B-like " Planets , 2001 .

[39]  B. Scott Gaudi,et al.  Prospects for the Characterization and Confirmation of Transiting Exoplanets via the Rossiter-McLaughlin Effect , 2006, astro-ph/0608071.

[40]  S. Baliunas,et al.  No Planet for Hd 166435 , 2022 .