Using Stellar Limb-Darkening to Refine the Properties of HD 209458b

We use multiband photometry to refine estimates for the planetary radius and orbital inclination of the transiting planet system HD 209458. We gathered 1066 spectra over four distinct transits with the STIS spectrometer on the Hubble Space Telescope using two gratings with a resolution R = 1500 and a combined wavelength range of 290-1030 nm. We divide the spectra into 10 spectrophotometric bandpasses, five for each grating, of equal wavelength span within each grating, and fit a transit curve over all bandpasses simultaneously. In our fit we use theoretical values for the stellar limb-darkening to further constrain the planetary radius. We find that the radius of HD 209458b is (1.320 ± 0.025)R_(Jup), which is a factor of 2 more precise than current estimates. We also obtain improved estimates for the orbital period P and time of center of transit T_C. Although in principle the photon-limited precision of the STIS data should allow us to measure the timing of individual transits to a precision of 2-7 s, we find that uncertainties in the stellar limb-darkening coefficients and residual noise in the data degrade these measurements to a typical precision of ±14 s. Within this level of error, we find no significant variations in the timing of the eight events examined in this work.

[1]  Orbital Perturbations of Transiting Planets: A Possible Method to Measure Stellar Quadrupoles and to Detect Earth-Mass Planets , 2001, astro-ph/0104034.

[2]  The color signature of the transit of HD 209458: discrepancies between stellar atmospheric models and observations , 2005, astro-ph/0510633.

[3]  Drake Deming,et al.  Infrared Observations during the Secondary Eclipse of HD 209458b. II. Strong Limits on the Infrared Spectrum Near 2.2 μm , 2003, astro-ph/0307297.

[4]  Accurate radius and mass of the transiting exoplanet OGLE-TR-132b , 2004, astro-ph/0407635.

[5]  T. Brown,et al.  Detection of Planetary Transits Across a Sun-like Star , 1999, The Astrophysical journal.

[6]  High-Resolution Spectroscopy of the Transiting Planet Host Star TrES-1 , 2004, astro-ph/0410483.

[7]  Drake Deming,et al.  Infrared radiation from an extrasolar planet , 2005, Nature.

[8]  Lunar,et al.  Refined Parameters of the Planet Orbiting HD 189733 , 2006, astro-ph/0603291.

[9]  R. Nichol,et al.  Cosmological parameters from SDSS and WMAP , 2003, astro-ph/0310723.

[10]  R. Gilliland,et al.  Detection of an Extrasolar Planet Atmosphere , 2001, astro-ph/0111544.

[11]  Peter Bodenheimer,et al.  On the Tidal Inflation of Short-Period Extrasolar Planets , 2001 .

[12]  Drake Deming,et al.  Infrared Observations During the Secondary Eclipse of HD 209458b: I. 3.6-Micron Occultation Spectroscopy Using the VLT , 2002 .

[13]  Drake Deming,et al.  A New Search for Carbon Monoxide Absorption in the Transmission Spectrum of the Extrasolar Planet HD 209458b , 2004, astro-ph/0412436.

[14]  M. Holman,et al.  Accepted for publication in the Astrophysical Journal Letters Obliquity Tides on Hot Jupiters , 2005 .

[15]  David Charbonneau,et al.  Hubble Space Telescope Time-Series Photometry of the Transiting Planet of HD?209458 , 2001 .

[16]  J. Valenti,et al.  Spectroscopic Properties of Cool Stars (SPOCS). I. 1040 F, G, and K Dwarfs from Keck, Lick, and AAT Planet Search Programs , 2005 .

[17]  H. J. Deeg,et al.  Probing the stellar surface of HD 209458 from multicolor transit observations , 2001 .

[18]  Michel Mayor,et al.  The missing link: A 4-day period transiting exoplanet around OGLE-TR-111 , 2004 .

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

[20]  Princeton,et al.  Theoretical Transmission Spectra during Extrasolar Giant Planet Transits , 1999, astro-ph/9912241.

[21]  R. P. Butler,et al.  A Transiting “51 Peg-like” Planet , 2000, The Astrophysical journal.

[22]  Dimitar D. Sasselov,et al.  HD 209458: Physical Parameters of the Parent Star and the Transiting Planet , 2001, astro-ph/0111494.

[23]  J. E. Stys,et al.  A Transiting Planet of a Sun-like Star , 2006 .

[24]  Steven Soter,et al.  Q in the solar system , 1966 .

[25]  R. Paul Butler,et al.  Measurement of Spin-Orbit Alignment in an Extrasolar Planetary System , 2005, astro-ph/0504555.

[26]  S. Jha,et al.  Multicolor Observations of a Planetary Transit of HD 209458 , 2000, astro-ph/0007245.

[27]  T. Brown.  Transmission Spectra as Diagnostics of Extrasolar Giant Planet Atmospheres , 2001, astro-ph/0101307.

[28]  T. Guillot,et al.  Giant Planets at Small Orbital Distances , 1995, astro-ph/9511109.

[29]  Tristan Guillot,et al.  Atmospheric circulation and tides of ``51 Pegasus b-like'' planets , 2002 .

[30]  A. Burrows,et al.  Theory of Extrasolar Giant Planet Transits , 2001, astro-ph/0101024.

[31]  Matthew J. Holman,et al.  The Use of Transit Timing to Detect Terrestrial-Mass Extrasolar Planets , 2005, Science.

[32]  The N2K Consortium. II. A Transiting Hot Saturn around HD 149026 with a Large Dense Core , 2005, astro-ph/0507009.

[33]  R. Paul Butler,et al.  On the Eccentricity of HD 209458b , 2005 .

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

[35]  Michel Mayor,et al.  ELODIE metallicity-biased search for transiting Hot Jupiters. II. A very hot Jupiter transiting the bright K star HD 189733 , 2005 .

[36]  S. Gavrilov,et al.  Love numbers of the giant planets , 1977 .

[37]  S. Peale,et al.  The tides of Io , 1981 .

[38]  Ignasi Ribas,et al.  A correlation between the heavy element content of transiting extrasolar planets and the metallicity of their parent stars , 2006, astro-ph/0605751.

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

[40]  Saurabh Jha,et al.  A Transiting Extrasolar Giant Planet around the Star OGLE-TR-10 , 2004 .

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

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

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

[44]  Saurabh Jha,et al.  New data and improved parameters for the extrasolar transiting planet OGLE-TR-56b , 2003 .

[45]  David Charbonneau,et al.  Transit Photometry of the Core-dominated Planet HD 149026b , 2005 .

[46]  Debra A. Fischer,et al.  A Comparison of Observationally Determined Radii with Theoretical Radius Predictions for Short-Period Transiting Extrasolar Planets , 2005 .

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