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 Rp /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 i = 85°.4+0°.9-0°.8 of and a planet radius of Rp = 0.755 ± 0.040 RJ. These measurements further support models in which the planet is greatly enriched in heavy elements.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science
- planetary systems
- techniques: photometric