THE DISCOVERY OF ELLIPSOIDAL VARIATIONS IN THE KEPLER LIGHT CURVE OF HAT-P-7

We present an analysis of the early Kepler observations of the previously discovered transiting planet HAT-P-7b. The light curve shows the transit of the star, the occultation of the planet, and the orbit phase-dependent light from the planet. In addition, phase-dependent light from the star is present, known as "ellipsoidal variations." The very nearby planet (only four stellar radii away) gravitationally distorts the star and results in a flux modulation twice per orbit. The ellipsoidal variations can confuse interpretation of the planetary phase curve if not self-consistently included in the modeling. We fit the light curve using the Roche potential approximation and derive improved planet and orbit parameters.

[1]  T. Guillot,et al.  The secondary eclipse of the transiting exoplanet CoRoT-2b , 2009, 0906.2814.

[2]  A. J. Drake.  On the Selection of Photometric Planetary Transits , 2003 .

[3]  W. D. Cochran,et al.  Kepler’s Optical Phase Curve of the Exoplanet HAT-P-7b , 2009, Science.

[4]  Richard S. Freedman,et al.  A Unified Theory for the Atmospheres of the Hot and Very Hot Jupiters: Two Classes of Irradiated Atmospheres , 2007, 0710.2558.

[5]  I. Hubeny,et al.  Theory for the Secondary Eclipse Fluxes, Spectra, Atmospheres, and Light Curves of Transiting Extrasolar Giant Planets , 2006, astro-ph/0607014.

[6]  R. E. Wilson.  Accuracy and efficiency in the binary star reflection effect , 1990 .

[7]  Sara Seager,et al.  The Very Low Albedo of an Extrasolar Planet: MOST Space-based Photometry of HD 209458 , 2007, 0711.4111.

[8]  L. J. Richardson,et al.  On the Dayside Thermal Emission of Hot Jupiters , 2005 .

[9]  S. Albrecht,et al.  The changing phases of extrasolar planet CoRoT-1b , 2009, Nature.

[10]  Howard Isaacson,et al.  Kepler Planet-Detection Mission: Introduction and First Results , 2010, Science.

[11]  Department of Physics,et al.  HAT-P-7b: An Extremely Hot Massive Planet Transiting a Bright Star in the Kepler Field , 2008, 0803.0746.

[12]  Motohide Tamura,et al.  First Evidence of a Retrograde Orbit of a Transiting Exoplanet HAT-P-7b , 2009, 0908.1673.

[13]  R. Kuschnig,et al.  An Upper Limit on the Albedo of HD 209458b: Direct Imaging Photometry with the MOST Satellite , 2006 .

[14]  R. P. Butler,et al.  System Parameters of the Transiting Extrasolar Planet HD 209458b , 2005, astro-ph/0504579.

[15]  M. R. Haas,et al.  INITIAL CHARACTERISTICS OF KEPLER LONG CADENCE DATA FOR DETECTING TRANSITING PLANETS , 2010, 1001.0256.

[16]  A. Loeb,et al.  Periodic Flux Variability of Stars due to the Reflex Doppler Effect Induced by Planetary Companions , 2003, astro-ph/0303212.

[17]  E. Pfahl,et al.  Ellipsoidal Oscillations Induced by Substellar Companions: A Prospect for the Kepler Mission , 2007, 0704.1910.

[18]  B. Gibson,et al.  Self-Consistent Massive Disks in Triaxial Dark Matter Halos , 2007, 0706.1357.

[19]  P. Quirion,et al.  ASTEROSEISMIC INVESTIGATION OF KNOWN PLANET HOSTS IN THE KEPLER FIELD , 2009, 1001.0032.

[20]  Alvaro Gimenez,et al.  Equations for the Analysis of the Rossiter-MCLaughlin Effect in Extrasolar Planetary Transits , 2006 .

[21]  C. Moutou,et al.  The secondary eclipse of CoRoT-1b , 2009 .

[22]  M. López-Morales,et al.  Thermal Emission from Transiting Very Hot Jupiters: Prospects for Ground-based Detection at Optical Wavelengths , 2007, 0708.0822.

[23]  Josef Kallrath,et al.  Eclipsing Binary Stars: Modeling and Analysis , 1999 .

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

[25]  David Charbonneau,et al.  A map of the day–night contrast of the extrasolar planet HD 189733b , 2007, Nature.