A Precise Estimate of the Radius of the Exoplanet HD 149026b from Spitzer Photometry
We present Spitzer 8 μm transit observations of the extrasolar planet HD 149026b. At this wavelength, transit light curves are weakly affected by stellar limb darkening, allowing for a simpler and more accurate determination of planetary parameters. We measure a planet–star radius ratio of R_p/R_★ = 0.05158 ± 0.00077, and in combination with ground-based data and independent constraints on the stellar mass and radius, we derive an orbital inclination of i = 85.◦4^(+0.◦9)_(−0.◦8) and a planet radius of R_p = 0.755 ± 0.040 R_J. These measurements further support models in which the planet is greatly enriched in heavy elements.
Additional Information© 2009 American Astronomical Society. Received 2008 May 6; accepted 2008 October 20; published 2009 February 18. We are grateful to F. van Leeuwen for providing parallax data for HD 149026, and to G. Takeda for discussions regarding the spectroscopic determination of stellar properties. We are especially grateful to G. Henry for sharing many seasons of photometric data. We would also like to thank an anonymous referee for specific and helpful recommendations. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech.
Published - 0004-637X_692_1_229.pdf
Accepted Version - 0805.0777.pdf